Matt's MCAT Flashcards

  1. 5' cap
    a methylated guanine nucleotide added to the 5' end of eukaryotic mRNA. The cap is necessary to initiate translation of mRNA
  2. A band
    The band of the sarcomere that extends the full length of the thick filament. The A band includes regions of thick and thin filament overlap
  3. Absolute refractory period
    A period of time following an action potential during which no additional action potential can be evoked regardless of the level of stimulation. (usually because Na+ channel closed whle K+ efflux)
  4. Accessory glands
    The three glands in the male reproductive system that reproduce semen: the seminal vesicles
  5. Accessory organs
    (1) In the GI tract
  6. Acetylcholine (Ach)
    The neurotransmitter used throughout the parasympathetic nervous system as well as the neuromuscular junction.
  7. Acetylcholinesterase (AChE)
    The enzyme that breaks down acetylcholine in the synaptic cleft.
  8. Acetyl-CoA
    The first substrate in teh Krebs cycle
  9. Acid hydrolases
    Enzymes that degrade various macromolecules and that require an acidic pH to function properly. Acid hydrolases are found within the lysosomes of cells.
  10. Acinar cells
    Cells that make up exocrine galnds
  11. Acrosome
    A region at the head of a sperm cell that contains digestive enzyems which
  12. Actin
    A contractile protein. In skeletal and cardiac muscle
  13. Action potential
    A localized change in a neruon's or musce cell's membrane potential that can propogate itself away from its point of origin. Action potentials are an all-or-none process mediated by the opening of voltage-gated Na+ and K+ channels when the membrane is brought to the threshold potential; opening of the Na+ channels causes a characteristic depolarization
  14. Activation energy (Ea)
    The amount of energy required to produce the transition state of a chemical reaction. If the activation energy for a reaction is very high
  15. Active site
    The 3D site of an enzyme where substrates (reactants) bind and a chemical reaction is facilitated.
  16. Active transport
    The movement of molecules through the plasma membrane against their concentration gradients. Active transport requires input of cellular energy
  17. Adenine
    One of the four aromatic bases found in DNA and RNA; also a component of ATP
  18. Adenohypophis
    anterior pituitary gland
  19. Adipocyte
    fat cell
  20. Adrenal medulla
    The inner region of the adrenal gland. The adrenal medulla is part of the sympathetic nervous systme
  21. Adrenergic tone
    A constant input to the arteries that keeps them somewhat constricted to maintain a basal level of blood pressure.
  22. Adrenocoricotropic hormone (ACTH)
    A trop hormone produced by the anterior pituitary gand that targets the adrenal cortex
  23. Afferent arteriole
    The small artery that carries blood toward the capillaries of the glomerulus.
  24. Afferent neuron
    A neuron that arries information (action potentials) to the central nervous system; a sensory neuron.
  25. Albumin
    A blood protein produced by the liver. Albumin helps to mantain blood osmotic pressure (oncotic pressure)
  26. Aldosterone
    The principal mineralocorticoid secreted by teh adrenal cortex. This steroid hormone targets the kidney tubules and increases renal reabsorption of sodium [and excretion of potassium]. (this causes ADH to be secreted & increased water comes out
  27. Alimentary canal
    "Also known as the gastrointestinal (GI) tract of the digestive tract
  28. Allosteric regulation
    The modifaction of enzyme activity through interactino of molecules with specific sites on the enzyme other than the active site (called allosteric sites)
  29. Alveoli
    (singular alveolus.) Tiny sacs
  30. Allele
    A version of a gene. For example
  31. Amino Acid
    The monomer of a protein; amino acids hae an amio group on one end fo the molecule and a carboxylic acid group on the other
  32. Amino acid acceptor site
    The 3' end of a tRNA molecule that binds an amino acid. The nucleotide sequence at this end is CCA
  33. Aminoacyl tRNA
    A tRNA with an amino acid attached. This is made by an animoacyl-tRNA synthetase specific to the amino acid being attache.d
  34. Aminion
    A sac filled with fluid (aminotic fluid) that surroudns and protects a developing embryo.
  35. Amphipathic
    The characteristics of amolecule that has both polar (hydrophilic) and non-polar hydrophobic) regions
  36. Amylase
    An enzyme that digests starch into disaccharides. Amylase is secreted by salivary glands and by the pancreas.
  37. Anabolism
    The process of bulidng complex structures out of simpler precursors
  38. Analogous structures
    Physical structures in two different organism that have funcitonal similarity due to their evoluntion in a common environment
  39. Anal sphincter
    The valve that controls the release of feces from the recturm. It has an internal part made of smooth muscle (thus involuntary) and an external part made of skeletal muscle (thus voluntary).
  40. Anaphase
    The third phase of mitosis. During anaphase
  41. Anaphase I
    The third phase of meiosis I. During anaphase I the rplicated homologous chromosomes are separated (the tetrad is split) and pulled to opposite sides of the cell.
  42. Anaphase II
    The third phase of meiosis II. During anaphase II the sister chromatids are finally spearated at their centromeres and puled to opposite sides of teh cell. Note that anaphase II is identical to mitotic anaphase
  43. Androgens
    Mal sex hormones. Testosteron is the primary androgen.
  44. Angiotensin
    A normal blood protein produced by the liver
  45. Antagonist
    Something that acts to oppose the action of something else. For example
  46. Anterioir pituitary gland
    Also known as the adenohypophysis
  47. Antibody (Ab)
    Also called immunoblobins
  48. Anticodon
    A sequence of three nucleotides (found int he anticodon loop of tRNA) that is complementary to a specific codon in mRNA. The codon to which the anticodon is complementary specifies the amino acid that is carried by that tRNA.
  49. Antidiuretic hormone (ADH)
    Also called vasopressin
  50. Antigen (Ag)
    A molecule (usually a protein) capable of initiating an immune repsonse (antibody production).
  51. Antigen presenting cell
    "Cells that possess MHC II (B cells and macrophages) and are able to display bits of ingested antigen on their surface in order to activate T cells. See also ""MHC"""
  52. Antiparallel orientation
    The normal configuration of double-stranded DNA in which the 5' end of oen strand is paired with the 3' end of the other
  53. Antiporter
    A carrier protein that transports two molecules acrss the plasma membrane in opposite directions.
  54. Aorta
    The largest artery in teh body; the aorta carries oxygenated blood away from the left ventricle of the heart.
  55. Appendix
    A mass of lymphatic tissue at the befenning of the large intestine that helps trap ingested pathogens.
  56. Aqueous humor
    A thin
  57. Arousal
    A function in the reproductive system
  58. Artery
    A blood vessel that carries blood away from the heart chambers. Arteries have muscular walls to regulate blood flow and are typically high-pressure vessles.
  59. A site
    Amino-acyl tRNA site; the site on a ribosome where a new amino acid is added to a growing peptide.
  60. ATP synthase
    A protein complex foudn in the inner membrane of the mitochondira. It is essentially a channel that llows H+ ions to flow from teh intermembrane space to the matrix (down teh gradeint produced by the enyzmes complexes of the electron transport chain); as the H= ions flow through the channel
  61. Atrioventricular bundle (AV) bundle
    Also known as the Bundle of His
  62. Atrioventricular (AV) node
    The second major node of the cardiac conduction system (after the SA node). The cardiac impulse is delayed slightly at teh AV node
  63. Atrioventricular valves
    The valves in the heart that separte the atria from teh ventricles. The tricuspid valve separates teh right atrium from the right ventricel
  64. Atrium
    One of the two small chambers in the heart that receive blood and pass it on to the ventricles. The right atrium receives deoxygenated blood from teh body through the superior and inferiro vena cavae
  65. Attachment
    The first step in viral infection. Attachemen of a virus to its host is very specific and is also known as adsorption.
  66. Auditory tube
    The tube that connects the middle ear acity with the pharynx; also known as the Eustachian tube. Its fucntion is to equalize midle ear pressure with atmospheric pressure so that pressure on boths sides of the tympanic membrane is the same.
  67. Autoimmune reaction
    An immune reaction directed against normal (necessary ) cells.Fo example
  68. Autonomic nervous system (ANS)
    The division of the periperal nervsous system that innervates and cotnrols the visceral organs (everything but the skeletal muscles). It is also knowns as the involuntary nervous system and an be subdivided into the sympathetic and parasympathetic divisions.
  69. Autosome
    A chromosome that does not determine gender (is not a sex chromosome). Humans have two sex chromsomes and 22 autosomes.
  70. Autotroph
    An organism that makes its own
  71. Auxotroph
    "A bacterium that cannon survive on minimal medium (glucose alone) because it lacks the ability to syntheisze a molecule it needs to live (typically an amino acid). Auxotrphs must ave the needed substance (the auxiliary trophic substance) added to their medium in order to survive. The are typically denoted by teh susbstance they require followed by a ""-"" sign in superscript. For example
  72. Avascular
    Lacking a blood supply; cartialge is an example of this
  73. Axon
    A long projection off the cell body of a neruon down which an action potential can be propagated.
  74. Bacilus
    A bacterium having a rod-like shaped (plural = bacilli).
  75. Bacteriophage
    A virus that infects a bacterium.
  76. Baroreceptor
    A sensory receptor that responds to hcanges in pressure; for example
  77. Basement membrane
    A layer of collagen fibers that separates epithelial tissue from connective tisse (example of epithelial cells in digestive tract) - they are actual connective tissue.
  78. Basilar membrane
    The flexible membrane in teh chochlea that supports the organ of Corti (structure which contains the hearing receptors). The fibers of the basilar membrane are short and stiff near the oval windown and long and fleaxible near the apex of the cochlea. This difference in structure allows the basilar membrane to help trasnduce pitch.
  79. B cell
    A type of lymphocyte that can recognize (bind to) an antigen adn secrete an antibody specific for that antigen. When activated by binding an antigen
  80. Bicarbonate
    HCO3-. THis ion results from the dissociation of carbonic acid
  81. Bile
    A green fluid made from cholesterol and secreted by teh liver. It is stored and concentrated in the gallbladder. Bile isn an amphipathic molecule that is secreted itno the small intestine when fats are present
  82. Binary fission
    An asexual method of bacterial reproduction that serves only to increase the size of the population; ther is no introduciton of gnetic diversity. THe bacterium simply grows in size until it has doubled its cellular components
  83. Bipolar neuron
    A neuron with a single axon and a single dendrite
  84. Blastocyst
    A fluid-filled sphere formed about 5 days after fertilization of an ovum that is made up of an outer ring of cells and inner cell mass. THis is the structure that implants in the endometrium of the uterus.
  85. Bohr effect
    The tendency of certain factors to stablize the hemoglobin in the tense conformation
  86. Bone marrow
    A non-bony material that fills the hollow spaces inside bones. Red bone marrow is found in regiosn of spongy bone and is the site of blood cell (red and white) production. Yellow bone marrow is found in the diaphysis (shaft) of long bones
  87. Bowman's capsule
    The region of the nephron that surrounds the glomerulus. The capsule ollects the plasma that is filtered from teh capillaries in the glomerulus.
  88. Bronchioles
    Very small air tubes int eh respiratory system (diameter 0.5 - 1.0 mm). The walls of the bronchioles are made of smooth muscle (thus involunatry) to help regulate air flow.
  89. Brush border enzymes
    Enzymes secreted by the mucosal cells lining the intestine. The brush border enzymes are disaccharides adn dipeptidases taht digest the smallest peptides and carbohydrates into their respective monomers.
  90. Bulbourethral galnds
    Small paired gland found inferior to the prostate in males and at the posterior end of the penile urethra. They secrete an alkaline mucus on sexual arousal that helps toneutralize any traces of acidic urine the urethra that might be harmful to sperm.
  91. Calcitonin
    A hormone produced by the C-cells of the thyroid gland that decreases serum calcium levels. It targets teh bones (stimulates osteoblasts)
  92. Calcitriol
    A hormone produced from vitamin D that acts in essentially the same manner as parathyroid hormone.
  93. Calmodulin
    A cyoplasmic Ca2+-binding protein. Calmodulin is particularly important in smooth muscle cells
  94. Canaliculus
    Very small tube or channel
  95. Capacitation
    An incrase in the fragility of the membranes of sperm cells when exposed to the female reproductive tract. Capacitation is required sot aht the acrosomal enzymes can be relased to faciliate fertilization.
  96. Capilary
    The smalles of all blodo vessles
  97. Capsid
    The outer protein coat of a virus (the whole coat)
  98. Carbohydrates
    Molecules made from monosaccharides that serve as the primary source of cellular energy
  99. Carbonic anhydrase
    An enzyme present in erythrocytes (as well as in other places) that catalyzes the conversion of CO2 and H2O into carbonic acid (H2CO3).
  100. Cardiac conduction system
    The specialized cells of the heart that spontaneously initiate action potentials and transmit them to the cardiac muscle cells. The cells of the conduction system are essentially cardiac muscle cells
  101. Cardiac muscle
    The muscle tissue of the heart Cardiac muscle is striated
  102. Cardiac output
    The volume of blood pumped out of the heart in one minute (vol/min); the product of the stroke volume (vol/beat) and the heart rate (beat/min). Cardiac output is directly proportional to blood pressure**.
  103. Carrier protein
    An integral membrane protein that undergoes a conformational change to move a molecule from one side of the membrane to another. See also 'uniporter'
  104. Cartilage
    A strong connective tissue with varying degrees of flexibility. (1) Elastic cartilage is the most flexible
  105. Catabolism
    The process of breaking down large molecules into smaller precursors
  106. Catalase
    The primary enzyme in peroxisomes; catalse catalyzes the hydrolysis of hydrogen peroxide (H2O2) into water and oxygen.
  107. Catalyst
    Something that increases the rate of a chemical reaction by reducing the activation energy for that reaction. The free energy of reaction remains unchanged.
  108. cDNA
    Complementary DNA. DNA produced synthetically by reverse trascribing mRNA. Because of eukaryotic mRNA splicing
  109. Cecum
    The first part of the large intestine.
  110. Cell surface receptor
    An integral membrane proteint hat binds extracellular signaling molecules
  111. Central canal
    The hollow center of an osteon
  112. Central chemoreceptors
    Receptors in the central nervous system that monitor the pH of cerebrospinal luid to help regulate ventilation rate.
  113. Central Nervous System
    The subdivision of the nervous system consisting of the brain and spinal cord.
  114. Centriole
    A structure composed of a ring of nine microtube triplets
  115. Centromere
    A structure near the middle of eukaryotic chromosomes to which the fibers of the mitotic spindle attach during cell division.
  116. Cerebellum
    The region of teh brain that coordinates and smooth skeletal muscle activity.
  117. Cerebral cortex
    A thin (4 mm) layer of gray matter on the surface of the cerebral hemispheres. The cerebral cortex is the conscious mind
  118. Cerebrospinal fluid
    A clear fluid the circulates around through the brain and spinal cord that helps to physially support teh brain and act as a shock absorber
  119. Ceruminous gland
    A gland that secretes a waxy product
  120. Cervix
    The opening to the uterus The ervix is typically plugged with a sticky acidic mucus during non-fertile times (to form a barrier against the entry of pathogens)
  121. Channel protein
    An integral protein that selectively allows molecules across the plasma membrane. See also entries under 'ion channel'
  122. Chemical synapse
    A type of synapse at which a chemical (a neurotransmitter) is released from teh axon of a neuron into the ysnaptic cleft where it binds to receptors on the next structure in sequence
  123. Chemoreceptor
    A sensory receptor that responds to specific chemicals. Some examples are gustatory (taste) receptors
  124. Chemotaxis
    Movement that is directed by chemical gradients
  125. Chemotroph
    An organism that relies on a chemical source of energy (such as ATP) instead of light (which phototrophs).
  126. Chief cells
    Pepsinogen-secreting cells foudn at teh bottom of the gastric glands
  127. Chitin
    A poysaccharide found in the cell walls of fungi and in the exoskeletons of insects.
  128. Cholecystokinin (CCK)
    A hormone secreted by the samll intestine (duodenum) in response to the presence of fats. It promotes release of bile from the gallbladder and pancreatic juice from the pancreas
  129. Cholesterol
    A large
  130. Chondrocyte
    A mature
  131. Chorion
    The portion of the placenta derived from the zygote.
  132. Choroid
    The darkly pigmented middle layer of the eyeball
  133. Chromosome
    A single piece of double-stranded DNA; part of the genome of an organism. Prokaryotes have circular chromosomes and eukaryotes have linear chromosomes.
  134. Chylomicron
    A type of lipoprotein; the form in which absorbed fats from the intestines are transported to the circulatory system.
  135. Chyme
    Partially digested
  136. Chymotrypsin
    One of the main pancreatic proteases; it is activated (from chymotrypsinogen) by trypsin.
  137. Cilia
    A hair-like structure on teh cell surface composed of microtubules ina '9+2' arrangement (nine pairs of microtubles surrounding 2 single microtubules in the center). Teh microtubules are conneted with a contractile protien called dynein. Cilia beat in a repetitive sweeping motion
  138. Ciliary muscles
    Muscles that help focus light on teh retin by controlling the curvature of the lens of the eye.
  139. Circular smooth muscles
    The inner layer of smooth muscle in the wall of the digestive tract. When the circular muscle contracts
  140. Clathrin
    A fibrous protein found on the intracellular side of the plasma membrane (also associated with the Golgi complex) that helps invaginate the membrane. Typically cel surface receptors are associated with clathrin-coated pits at the plasma membrane binding of the ligan to the receptor trigger invagination (example: cholesterol uptake via lipoprotein endocytosis).
  141. Cleavage
    The rapid mitotic division of a zygot that being within 24-36 hours after fertilization
  142. Coccus
    A bacteria having a round shape (plural = cocci)
  143. Cochlea
    The curled structure in the inner ear that contains the membranes and hair cells that transduce sound waves into action potentials.
  144. Codominance
    A situation in which a heterozygote displays the phenotype associated with each of the alleles
  145. Codon
    A group of three nucleotides taht is specific for a particular amino acid
  146. Coenzyme
    An **organic molecuel taht associates non-covalently with an enzyme
  147. Cofactor
    An **inorganic molecule that associates non-covalently with an enzyme and that is required for the proper functioning of the enzyme
  148. Collagen
    A protein fiber with a unique triple-helix that gives it great strength. Tissues with a lot of collagen fibers are typically very strong
  149. Collecting duct
    The portion of the nephron where water reabsorption is regulated via antidiuretic hormone (ADH). Several nephrons empty into each collecting duct
  150. Common bile duct
    The duct that carries bile from the gallbladder and liver to the small intestine (duodenum).
  151. Compact bone
    A dense
  152. Competitive inhibitor
    An enzyme inhibitor that competes with substrate for binding at the active site of teh enzyme. When the inhibitor is bound
  153. Complement system
    A group of blood proteins that bind non-specifically to the surface proteins of foreign cells (such as bacteria)
  154. Cones
    Photoreceptors in the retina of the eye that responds to bright light and provide color vision.
  155. Conjugation
    A form of genetic recombination in bacteria in which plasmid and/or genomic DNA is transferred from one bacterium to the toher through a conjugation bridge.
  156. Connective tissue
    One of the four basic tissue types in the body (epithelial
  157. Convergent evolution
    A form of evolution in which different organisms are placed into the same environment and exposed to teh same selection pressures. This causes the organisms to evolve along similar lines. As a result
  158. Cooperativity
    A type of substrate binding to a multi-active site enzyme
  159. Cornea
    The clear portion of the tough outer layer of teh eye ball
  160. Corona radiata
    The layer of granulosa cells taht surround an oocyte after is has been ovulated.
  161. Coronary vessels
    The blood vessels taht carry blood to and from cardiac muscle. The coronary arteries branch off teh aorta and carry oxygenated blood to the cardiac tissue. The coronary veins collect deoxygenated blood from teh cardiac tissue
  162. Corpus callosum
    The largest bundle of white matter (axons) connecting th two cerebral hemispheres.
  163. Corpus luteum
    'Yellow body.' The remnants of an ovarian follicle after ovulation has occurred. The cells enlarge and begin secreting progesterone
  164. Cortex
    The outer layer of an organ
  165. Corticosteroids
    Steroid hormones secreted from the adrenal cortex. The two major classes are teh mineralocorticoids and glucocorticoids. Aldosterone is the principal mineralocorticoid
  166. Cortisol
    The principal glucocorticoid secreted from teh adrenal cortex. This steroid hormone is released ruing stress
  167. Creatine Phosphate
    An energy storage molecule used by muscle tissue. The phosphate from creatine phosphate can be removed and attached to an ADP to generate ATP quickly.
  168. Cristae
    The folds of the inner membrane of a mitochondrion
  169. Cross bridge
    The connection of a mosin head group to an actin filament during muscle contraction (the sliding filament theory).
  170. Crossing over
    The exchange of DNA between paired homologus chromosomes (tetrads) during *prophase I* of meiosis.
  171. Cyclic AMP (cAMP)
    A cyclic version of adenosine monophosphate
  172. Cytokinesis
    The phase of mitosis during which the cell physically splits into two daugter cells. Cytokinesis begins near the end of anaphase
  173. Cytosine
    One of the four aromatic bases found in DNA and RNA. Cytosine is a pyrimidine; it pairs with guanine.
  174. Dendrite
    A projection of the cell body of a neuron that recieves a nerve impulse form a different neuron and send the impulse to the cell body. Neurons can have one or several dendrites!
  175. Dense connective tissue
    Connective tissue with large amounts of either collagen fibers (making them strong) or elastic fibers
  176. Depolarization
    The movement of teh membrane potential of a cell away from rest potential in a more positive direction.
  177. Dermis
    A layer of connective tissue underneath the epidermis of the skin. The dermis contains blood vessels
  178. Desmosome
    A general cell junction
  179. Determination
    The point during development at which a cell becomes committed to a particular fate (sensory
  180. Diaphragm
    The primary muscle of inspiration. The diaphragm is stimulated to contract at regular intervals by the respiratory center in the medulla oblongata (via the phrenic nerve). Although it is made of skeletal muscle (and can therefore be voluntary controlled)
  181. Diaphysis
    The shaft of a long bone. The diaphysis is hollow and is made entirely from compact bone.
  182. Diastole
    The perio of time during which the ventricles of the heart are relaxed.
  183. Diastolic pressure
    The pressure measured in the arteries while the ventricles are relaxed (during diastole).
  184. Diencephalon
    The portion of theforebrain that includes the thalamus and hypothalamus.
  185. Differentiation
    The specialization of cell types
  186. Diffusion
    The movement of a particle (the solute) in a solution from its region of high concentration to its region of low concentration ( or down it concentration gradient).
  187. Diploid organism
    An organism that has two copies of its genome it each cell. The paired genomes are said to be homologous.
  188. Disaccharide
    A molecule composed of two monosaccharides. Common disaccharides include maltose
  189. Distal convoluted tubule
    The portion of the nephron tubule after the loop of Henle
  190. Divergent evolution
    A form of evolution in which the same organism is placed into different environments with different selection pressures. This causes organisms to evolve differently
  191. DNA polymerase
    Also called DNA pol
  192. Dominant
    The allele in a heterozygous genotype that is expressed; the phenotype resulting from either a heterozygous genotype or a homozygous dominant genotype.
  193. Dorsal root ganglion
    A group of sensory neuron cell bodies found just posterior to the spinal cord on either side. A pair of root ganglia exists for each spinal nerve that expands from the spinal cord. The ganglia are part of the peripheral nervous system (PNS).
  194. Downstream
    Toward the 3' end of an RNA transcript (the 3' end of the DNA coding strand). Stop codons and (in eukaryotes) the pol-A tail are found 'downstream.'
  195. Duodenum
    The first (approximately 5%) of the small intestinte.
  196. Dynein
    A contractile protein connecting microtubules in the '9+2- arrangement of cilia and eukaryotic flagella. The contraction of dynein produces the characteristic movement of these structures.
  197. Ectoderm
    One of the three primary (embryonic) germ layers formed during gastrulation. Ectoderm ultimately forms external structures such as the skin
  198. Edema
    Swelling of tissues
  199. Effector organ
    The organ that carries out teh command sent along a particular motor neuron
  200. Efferent arteriole
    The small artery that carries blood away from the capillaries of the glomerulus.
  201. Efferent neuron
    A neuron that carries information (action potentials) away from the central nervous system; a motor neuron.
  202. Ejaculation
    A subphase of male orgasm
  203. Ejection fraction
    The fraction of teh end-diastolic volume ejected from the ventricles in a single contraction of teh heart. THe ejection fraction is normally around 60% of the end diastolic volume.
  204. Elastin
    A fibrous
  205. Electrical synapse
    A type of syanpse in which the cells are connected by gap junctions
  206. Electron transport chain
    A series of enzyme complexes found along the inner mitochondrial membrane. NADH and FADH2 are oxidized by tehse enzymes; the electrons are shuttled down the chain and are ultimately passed to oxygen and to produce water. The electron energy is used to pump H+ out of the mitochondrial membrane; the resulting H+ gradient is subsequently used to drive the production of ATP.
  207. Embryonic stage
    The period of human development from implantation through 8 weeks of gestation. Gastrulation
  208. Emission
    A subphase of male orgasm. Emission is the movement of sperm (via the vas deferens) and semen into the urtehra in prepartion for ejaculation.
  209. Endocrine gland
    A ductless gland that secretes a hormone into the blood
  210. Endocrine system
    A systme of ductless glands taht secrete chemical messengers (into) the blood - has to be into the blood.
  211. Endocytosis
    The uptake of material into a cell
  212. Endoderm
    One of the three primary (embryonic) germ layers formed during gastrulation. Endoderm ultimately forms internal structures
  213. Endometrial cycle
    The 28 days of the menstrual cycle as they apply to the events in the uterus. The endometrial cycle is also known as the uterine cycle
  214. Endometrium
    The inner epithelial lining of the uterus that thickens and develops during the menstrual cycle
  215. Endospore
    A bacterial structure formed in unfavorable growth conditions. Endospores have very rough outer shells made of peptidoglycan and can survive harsh conditions. The bacterium inside the endospore is essentially dormant and can become active (called germination) when conditions again become favorable.
  216. Endosymbitoic theory
    the theory that mitochondria and chloroplasts originated as independent unicellular organsims living in symbiosis with larger cells
  217. Endotoxin
    A normal component of the outer membrane of Gram-negative bacteria. Endotoxins produce extreme immune reactions (septic shock)
  218. End plate potential
    The depolarzation of the motor end plate on a muscle cell.
  219. Enteric nervous system
    The nervous system of the gastrointestinal tract. It controls secretion and motility within teh Gi tract
  220. Enterogasterone
    A hormone secreted by the small intestine (duodenum) in response to the presence of food. It decreases the rate at which chyme leaves the stomach and enters the small intestine.
  221. Enterokinase
    A duodenal enzyme that activates trypsinogen (from the pancreas) to trypsin.
  222. Envelope
    A lipid bilayer that surrounds the capsid of an animal virus. the envelope is acquired as teh virus buds out through the plasma membrane of its host cell. Not all annimal viruses possess and envelope.
  223. Enzyme
    A physiological catalyst. Enzymes are usually proteins
  224. Epidermis
    The outermost layer of teh skin. The epidermis is made of epithelial tissue that is constantly dividing at the bottom; teh cells migrate to teh surface (dying along the way) to be sloughed off at the suface.
  225. Epididymis
    A long
  226. Epiglottis
    A flexible piece of cartilage in the larynx that flips downward to seal teh trachea during swallowing.
  227. Epinephrine
    A hormone produced and secreted by teh adrenal medulla that prolongs and increases teh effects of the sympathetic nervous system.
  228. Epiphyseal plate
    A band of carilage (hyaline) found between the diaphysis and epiphyses of long bones during childhood and adolescence. Cell proliferation in the middle of the eiphyseal plate essentially forces teh diaphysis and epiphyses further apart
  229. Epiphysis
    One of the two ends of long bone (pl: eiphyses). The epiphyses have an outer shell made of compact bone and inner core of spongy bone. The spongy bone is filled with red bone marrow
  230. Epistasis
    A situation in which the expression of one gene prevents expression of all allelic forms of another gene
  231. Epithelial tissue
    One of the four basic tissue types in the body (epithelial
  232. Epitope
    The specific site on an antigenic molecule that binds to a T cell receptor or to an antibody.
  233. EPSP
    Excitatory postsynaptic potential; a slight depolarization of a postsynaptic cell
  234. Erectile tissue
    Specialized tissue with a lot of space that can fill with blood upon proper stimulation
  235. Erythrocyte
    A red blood cell; they are filled with hemoglobin
  236. Erythropoietin
    A hormone produced and released by the kidney that stimulates the production of red blood cells by the bone marrow.
  237. Estrogen
    The primary female sex hormone. Estrogen stimulates the development of female secondary sex characteristics during puberty
  238. Euchromatin
    DNA that is loosely packed around histones. This DNA is more accessible to enzymes and the genes in euchromatin can be activated if needed.
  239. Eukaryotic
    A cell characterized by the presence of a nucleus and other membrane-bound organelles. Eukaryotes can be unicellular (protists) or multicellular (fungi
  240. Exclusion
    The removal ( and usually the activation) of a viral genome from its host's genome.
  241. Excitation-contraction coupling
    The mechanism that ensures tehat skeletal muscle contraction does not occur without neural stimulation (excitation). A trest
  242. Excretion
    The elimination of wastes from the body.
  243. Exocrine gland
    A gland that secretes its product into a duct
  244. Exocytosis
    The secretion of a cellular product to the extracellular medium through a secretory vesicle.
  245. Exon
    A nucleotide sequence in RNA that contains protein-coding information. Exons are typically separated by introns (intervening sequences) that are spliced out prior to translation.
  246. Exotoxin
    A toxin that secreted by a bacterium into its surrounding medium that help the bacterium compete with other species. Some exotoxins cause serious disease in humans (botulism
  247. Expiration
    The movement of air out of the respiratory tract. Expiration can be passive (caused by relaxation of the diaphragm and elastic recoil of the lungs) or active (caused by contraction of the abdominal muscles
  248. Facilitated diffusion
    Movement of a hydrophilic molecuel across the plasma membrane of a cell
  249. Facultative anaerobe
    An organism that will use oxygen (aerobic metabolism) if it is available
  250. FADH2
    The reduced from (carries electrons) of FAD (flavin adenine dinucleotide). this is the other main electron carrier in cellular respiration (NADH is the most common).
  251. Fascicle
    A bundle of skeletal muscle cells. Fascicles group together to form skeletal muscles.
  252. Fast block to polyspermy
    The depolarization of the egg plasma membrane upon fertilization
  253. Feedback inhibition
    Also called negative feedback
  254. Fermentation
    The reduction of pyruvate to either ethanol or lactate in order to regenerate NAD+ from NADH. Fermentation occurs in the absence of oxygen
  255. Fertilization
    The fusion of a sperm with an ovum during sexual reproduction. Fertilization typically occurs in the uterine tubes and requires capacitation of the sperm and relase of the acrosomal enzymes. Fertilization is a species-specific process
  256. F (fertility) factor
    A bacterial extrachromosal elent that allows the bacterium to initati conjugation. Bacteria that possess teh F factor are known as F+ 'males'.
  257. Fetal stage
    The period of human development beginning at 8 weeks of gestation and lasting until birth (38-42 weeks of gestation). During this stage the organs formed in the embryonic stage grow and mature. The developing baby is known as a fetus during this time period.
  258. Fibrinogen
    A blood protein essential to blood clotting. The conversion of fibrinogen to its active form (fibrin) is among the final steps in clot formation
  259. Fibroblast
    A generic connective tissue cell that produces fibers; the progenitor of all other connective tissue cell types.
  260. Filtration
    The movement of a substance across a membane via pressure. In the kidney
  261. Fimbriae
    Fingerlike projection of the uterin (fallopian) tubes that drape over the ovary.
  262. First law of Thermodynamics
    The law of conservation of energy; the energy of the universe is constant
  263. Flagella
    A long
  264. Fluid mosaic model
    the current understanding of membrane structure
  265. Follicle
    A developing oocyte and all of its surrounding (supporting) cells.
  266. FSH
    A tropic hormone produced by the anterior pituitary gland that targets the gonads. In females
  267. Follicular phase
    The first phase of the ovarian cycle
  268. F1 generation
    The first generation of offspring from a given genetic cross.
  269. Formed elements
    The cellular elements of blood; erythrocytes
  270. Frameshift mutation
    A mutation caused by an insertion or deletion of base pairs in a gene sequence in DNA such that the reading frame of the gene (and thus teh amino acid sequence of the protein) is altered.
  271. Frank Starling mechanism
    A mechanism by which the stroke volume of the heart is increased by increasing the venous return of the heart (thus stretching the ventricular muscle).
  272. Functional synctium
    A tissue in which the cytoplasms of the cells are connected by gap junctions
  273. Gallbladder
    A digestive accessory organ near the liver. The gallbladder stores and concentrates bile produced by the liver
  274. Gametogenesis
    The formation of haploid gametes (sperm or ova) via meiosis.
  275. Ganglion
    A clump of gray matter (unmyelinated neuron cell bodies) found in the peripheral nervous system.
  276. Gap junction
    A junction between cells
  277. Gap phase
    A phase in the cycle between mitosis and S phase (G1) or between S phase and mitosis (G2). During gap phases the cell undergoes normal activity and growth; G1 may include preparation for DNA replication and G2 includes preparation for mitosis. Note that non-dividing cells remain permanently in G1
  278. Gastrin
    A hormone released by teh G cells of the stomach in the presence of food. Gastrin promotes muscular activity of the stomach as well as secretion of hydrochloric acid
  279. Gastrulation
    the division of the inner cell mass of a blastocyst (developing embryo) into the three primary germ layers. Gastrulation occurs during weeks 2-4 of gestation.
  280. Gene
    A portion of DNA that codes for some product
  281. Gene pool
    The sum of all genetic material in a population.
  282. Genetic code
    The 'language' of a molecular biology that specifies which amino acid corresponds to which three-nucleotide group (codon).
  283. Genome
    All the genetic information in an organism; all of an organism's chromosomes.
  284. Genotype
    The combination of alleles of an organism carries. In a homozygous genotype
  285. Gibbs free energy
    The energy in a system that can be used to drive chemical reactions. If the change in free energy of a reaction (Delta G
  286. Glomerulus
    The ball of capillaries at the beginning of the nephron where blood filtration takes place.
  287. Glucagon
    A peptide hormone produced and secreted by the alpha cells
  288. Glycolipid
    A membrane lipid consisting of a glycerol molecule esteried to two fatty acid chains and a sugar molecule.
  289. Goblet cells
    Unicellular exocrine glands found along the respiratory and digestive tracts taht secrete mucus.
  290. Golgi apparatus
    A stack of membranes found near the rough ER in eukaryotic cells that is involved in the secretory pathway. The Golgi is involved in protein glycosylation (and other protein modification) and sorting and packagin proteins.
  291. Gonadotropin releasing hormone (GnRH
    A hormone released from the hypothalamus that triggers the anterior pituitary to secrete FSH and LH.
  292. Gonadotropins
    Anterior pituitary topic hormones FSH (follicle stimulating hormone) and LH (luteinizing homeon) that stimulates the gonads (testes and ovaries) to produce gametes and to secrete sex steroids.
  293. G-protein linked receptor
    A cell surface receptor associated with an intracellular protein that binds and hydrolyzes GTP. When GTP is bound
  294. Graafian follicle
    A large
  295. Gram-negative bacteria
    Bacteria that have a thin peptidoglycan cell wall covered by an outer plasma membrane. They stain very lightly (pink) in Gram stain. Gram-negative bacteria are typically more resistant to antibiotics than Gram-positive bacteria.
  296. Gram-positive bacteria
    Bacteria that have a thick peptido glycan cell wall
  297. Granulosa cells
    the majority of the cells surrouding an oocyte in a follicle. Granulosa cells secrete estrogen during the follicular phase of the ovarian cycle (before ovulation).
  298. Gray matter
    Unmyelinated neuron cell bodies and short unmyelinated axons.
  299. Growth hormone
    A hormone released by the anterior pituitary that targets all cells in the body. Growth hormone stimulates whole body growth in children and adolescents
  300. Guanine
    One of the four aromatic bases found in DNA and RNA. Guanine is a purine; it pairs with cytosine.
  301. Gustatory receptors
    Chemoreceptors on the tongue that respond to chemicals in a food.
  302. Gyrase
    A prokaryotic enzyme used to twist teh single circular chromosome of prokaryotes upon itself to form supercois. Supercoiling helps to compact prokaryotic DNa and make it sturdier.
  303. Hair cells
    Sensory receptors found in the inner ear. Cochlear hair cells respond to vibration in the cochlea caused by sound waves and vestibular hair cells respond to changes in position and acceleration (used for balance).
  304. Haploid organism
    An organism that has only a single copy of its genome in each of its cells. Haploid organisms possess no homolous chromosomes.
  305. Hardy-Weinberg law
    A law of population genetics that states that the frequencies of alleles in a given gene pool do not change over time. There are five assumptions required for this law to hold true: there must be no mutation
  306. hCG
    Human Chorionic Gonadotropin
  307. Helicase
    An enzyme that unwinds the double helix of DNA and separates the DNA strands in preparation for DNA replication.
  308. Hematocrit
    The percentage of wholeblood made up of erythrocytes The typical hematocrit value is between 40-45%.
  309. Hematopoiesis
    The synthesis of blood cells (occurs in the red bone marrow)
  310. Hemizygous gene
    A gene appearing in a single copy in diploid organisms
  311. Hemoglobin
    A four-subunit protein found in red blood cells that binds oxygen. Each subunit contains a heme group
  312. Hemophilia
    An X-linked recessive disorder in which blood fails to clot properly
  313. Hemostasis
    The stoppage of bleeding; blood clotting.
  314. Hepatic portal vein
    A vein connecting the capillary bed of the intestines with the capillary bed of the liver. This allows amino acids and gluocse absorbed from the intestines to be delivered first to the liver for processing before being transported throughout the circulatory system.
  315. Heterochromatin
    DNA that is densely packed around histones. The genes in heterochromatin are generally inaccessible to enzymes and are turned off.
  316. Heterotroph
    An organism that cannot make its own food
  317. Heterozygous
    A genotype in which two different alleles are possessed for a given gene.
  318. Hexokinase
    The enzymes that catalyzes the phosphorylation of glucose to form glucose-6-phosphate in the first step of glycolysis. This is one of the ain regulatory steps of this pathway. Hexokinase is feedback-inhibited by glucose-6-P.
  319. Hfr bacterium
    High frequency of recombination bacterium An F+ bacterium that has the fertility factor integrated into its chromosome. When conjugation takes place
  320. Histones
    Globular protein that assist in DNA packaging in eukaryotes. Histones form octamers around which DNA is wound to form a nucleosome.
  321. hnRNA
    Heterogeneous nuclear RNA; the primary transcript made in eukaryotes before splicing.
  322. Homeostasis
    The maintenance of relatively constant internal conditions (such as temperature
  323. Homologous chromosomes
    A pair of similar chromosomes that have the same genes in the same order
  324. Homologous structures
    Physical structures in two different organisms that have structural similarity due to a common ancestor
  325. Homozygous
    A genotype in which two identical alleles are possessed for a given gene. The allelles can both be dominant (homozygous dominant) or both be recessive (homozygous recessive)
  326. Humoral immunity
    Specif ic defense of the body by antibodies
  327. Hydroxyapatite
    Hardy crystals consisting of calcium and phosphate that form the bone matrix.
  328. Hyperpolarization
    The movement of the membrane potential of a cell away from rest potential in a more negative direction.
  329. Hypodermis
    Aso called a subcutaneous layer
  330. Hypophysis
    The pituitary gland.
  331. Hypothalamic-pituitary portal system
    A set of veins that connect a capillary bed in the hypothalamus (the primary capillary plexus) with a capillary bed in the anterior pituitary gland (the secondary capillary bed). Releasing and inhibiting factors from the hypothalamus travel along the veins to directly affect cells in the anterior pituitary.
  332. Hypothalamus
    The portion of the diencephalon involved in maintaining body homeostasis. the hypothalamus also controls the release of hormones from the pituitary gland.
  333. H zone
    The region at the center of an A band of a sarcomere that is made up of myosin only. The H zone gets shorter (and may disappear) during muscle contraction.
  334. I band
    The regino of the sarcomere made up only of thin filaments. The I band is bisected by a Z line. I bands alternate with A bands to give skeletal and cardiac muscle a striated appearance. I bands get shorter (and may disappear completely) during muscle contraction.
  335. Ileocecal valve
    The sphincter that separates the final part of the small intestine (the ileum) from the fron part of the large intestine (the cecum). It is typically kept contracted (closed) so that chyme can remain in the small intestine as long as possible. The ileocecal valve is stimulated to relax by the presence of food in the stomach.
  336. Ileum
    The final section (approximately 55%) of the small intestine.
  337. Implantation
    The burrowing of a blastocyst (a developing embryo) into the endometrium of the uterus
  338. Incomplete dominance
    A situation in which a heterozygot displays a blended version of the pheotypes associated with each allele
  339. Inducible enzymes
    An enzyme whose transcription can be stimulated by an abundance of its substrate (as opposed to repressible enzyme). Usually in catabolism.
  340. Induction
    The process by which neighboring cells can influence the determination (and subsequent differentiation) of a cell.
  341. Inflammation
    An irritation of a tissue caused by infection or injury. Inflammation is characterized by four cardinal symptoms; redness (rubor)
  342. Inhibin
    A protein hormone secreted by sustenacular cells of the testes that acts to inhibit the release of FSH and LH from the anterior pituitary.
  343. Innate immunity
  344. Inner cell mass
    The mass of cells in the blastocyst that ultimately give rise to the embryo and other embryonic structues (the amion
  345. Inspiration
    The movement of air into the respiratory tract. Inspiration is an *active process*
  346. Insulin
    A peptide hormone produced and secreted by the Beta cells of the pancreas. Insulin targets cells in the body
  347. Integral membrane protein
    A protein embedded in the lipid bilayer of a cell. These are typicallly cell surface receptors
  348. Intercalcated discs
    The division between neighboring cardiac muscle cells. Intercalcated discs include gap junctions
  349. Intercostal muscles
    Muscles located in between the ribs that play a role in ventilation.
  350. Interleukin
    A chemical secreted by a T cell (usually the helper Ts) that stimulates activation and proliferation of other immune system cells.
  351. Intermediate filaments
    Cytoskeletal filaments with a diameter in between that of the microtubule and the microfilament. Intermediate filaments are composed of many different proteins and tend to play structural roles in cells.
  352. Interneuron
    A neuron found completely within the central nervous system. Interneous typically connect sensory and motor neurons
  353. Internodal tract
    The portion of the cardiac conduction system between the SA node and the AV node.
  354. Interphase
    All of the cell cycle except for mitosis. Interphase includes G1
  355. Interstitial cell
    Also called Leydig cells
  356. Intron
    A nucleotide sequence that intervenes between protein-coding sequences. In DNA
  357. Ion channel
    A protein channel in a cell membrane that is specific for a particular ion
  358. IPSP
    Inhibitory postsynaptic potential; a slight hyperpolarization of the postysynaptic cell
  359. Iris
    A pigmented membrane found just in from the lens of the eye. In the center of iris is the pupil
  360. Islets of Langerhans
    "Also called simply
  361. Jejunum
    The middle (approximtely 40%) of the small intestine.
  362. Juxtaglomerular apparatus (JGA)
    A contact point between the afferent arteriole of the glomerulus and the distal convoluted tubule of the nephron. It is involved in regulating blood pressure.
  363. Juxtaglomerular cells.
    The cells of the afferent artery at the juxtaglomerular apparatus. They are baroreceptors that secrete renin upon sensing a decrease in blood pressure.
  364. Keratin
    A protein-based substance secreted by cells of the epiderms as they migrate outward. The keratin makes the cells tougher (better able to withstand abrasion) and helps make the skin waterproof.
  365. Kinase
    An enzyme that phosphorylates something else. Kinases are frequently used in regulatory pathways
  366. Krebs cycle
    The third stage of cellular respiration
  367. Labia
    The folds of skin that enclose the vaginal and urethral openings of females.
  368. Labor contractions
    Strong contractions of the uterus (stimulated by oxytoncin) that force a baby out of the mother's baby during childbirth. Labor contractions are part of a positive feedback cycle
  369. Lacteals
    Specialized lymphatic capillaries in the intestines that take up lipids as well as lymph.
  370. Lactic acid
    Produced in muscle cells from the reduction of pyruvate (under anaerobic conditions) to regenerate NAD+ so that glycolysis can continue. A rise in lactic acid usually accompanies an increase in physical activity.
  371. Lacunae
    Small cavities in the bone or cartilage that hold individual bones or cartilage cells.
  372. Lagging strand
    The newly forming daughter strand of DNA that is replicated in a discontinuous fashion
  373. Lag phase
    A short period of time **prior to exponential growth of a bacterial population during which no
  374. Large intestine
    The final phase of the digestive tract
  375. Larynx
    A rigid structure at the top of the trachea (so it is part of trachea
  376. Law of Independent Assortment
    Mendel's seond law. States that genes found on different chromosomes
  377. Law of Segregation
    Mendels' first law. The Law of Segregation states that the two alleles of a given gene will be separate from one another during gamete formation (meiosis).
  378. Lawn
    A dense grwoth of bacteria that covers the surface of a petri dish.
  379. Leading strand
    The newly forming daughter strand of DNA that is replicated in a continuous fasion; the daughter strand that is replicated in thes aem direction that parental DNA is unwinding.
  380. Leak channel
    An ion channel that is constitutively open
  381. Length-tension relationship
    The relationship of muscle length to its ability to generate strong contractions. Maximum tension (contraction strength) is achieved at sarcomere lengths between 2.0 and 2.2 microns. Tension decreases outside of this range <-- remember.
  382. Leukocyte
    A type of white blood cell; leukocytes are either B or T cells and are involved in disease defense.
  383. Ligament
    A strong band of connective tissue that connets bones to one another.
  384. Ligand
    The specific molecule that binds to a receptor.
  385. Ligand-gated ion channel
    An ion channel that is opened or closed based on the binding of a specific ligand to teh channel. Once opened
  386. Ligase
    An enzyme that connects two fragments of DNA to make a single fragment; also called DNA ligase. This enzyme is usedd during DNA replication and is also used in recombinant DNA research.
  387. Lipoprotein
    Large conglomerations of proteins
  388. Linkage
    The failure of two separate genes to boey the Law of Independent Assortment
  389. Lipid
    A hydrophobic molecule
  390. Liver
    The largest organ in the abdominal cavity. The liver has many roles
  391. Local autoregulation
    The ability of tissues to regulate their own blood flow in the absence of neural stiulation. THis is generally accomplished via metabolic wastes (such as CO2) that act as vasodilators.
  392. Log phase
    The period of exponential growth of bacterial population.
  393. Long bone
    The most common class of bone in the body
  394. Longitudinal muscle
    The outer layer of smooth muscle in the wall of the digestive tract. When the longitudinal muscle contracts the tube shortens.
  395. Loop of Henle
    The loop of the nephron that dips downward into the renal medulla. The loop of Henle sets up a concentration gradient in the kidney such that from the cortex to the renal pelvis osmolarity increases. The descending limb of the loop of Henle is permeable to water
  396. Loose connective tissue
    Connective tissue that lacks great amount of collagen or elastic fibers (hence
  397. Lower esophageal sphincter
    Formerly called the cardiac sphincter
  398. Lumen
    The inside of the a hollow organ (e.g.
  399. Luteal phase
    The third phase of the ovarian cycle
  400. Luteinizing Hormone (LH)
    A tropic hormone produced by the anterior pituitary gland that targets the gonads. In females LH triggers ovulation and the development of a corpus luteum during the menstrual cycle; in males
  401. Lymphatic system
    A set of vessels in the body that runs alongside the vessels of the circulatory system. It is a one-way system
  402. Lymph node
    A concentrated region of white blood cells found along the vessels of the lympatic system.
  403. Lymphocyte
    The second most common of the five classes of leukocytes. Lymphocytes are involved in specific immunity and include two cell types
  404. Lymphokine
    A chemical secreted by a T cell (usually the helper Ts) that stimulates activation and proliferation of other immune system cells.
  405. Lysogenic cycle
    A viral life cycle in which the viral genome is incorporated into the host genome where it can remain dormant for an unspecified period of time. Upon activation
  406. Lysosome
    A eukaryotic organelle filled with digestive enzymes (acid hydrolases) that is involved in digestion of macromolecules such as worng organelles or material ingested by phagocytosis.
  407. Lysozyme
    An enzyme that lyses bacterial cell walls. Lysozyme is produced in the end stages of the lytic cycle so that new viral particles can escape their hosst; it is also found in human tears and human saliva.
  408. Lytic cycle
    "A viral life cycle in which the host is turned into a ""virus factory"" and ultimately lysed to release the new viral particles."
  409. Macrophage
    A large
  410. Macula densa
    The cells of the distal tubule at the juxtaglomerular apparatus. They are receptors that monitor filtrate osmolarity as a means of regulatin filtration rate. If a drop is osmolarity is sensed
  411. Maternal inheritance
    Genes that are inherited only from the mother
  412. Matrix
    The interior of a mitochondrion (the region bounded by the inner membrane).
  413. Mechanoreceptors
    A sensory receptor that responds to mechanical disturbances
  414. Medium
    The environment in which or upon which bacteria grow. It typically contains a sugar source and any other nutrients that bacteria may require. 'Minimal medium' contain nothing but glucose.
  415. Medulla
    The inner region of an organ
  416. Medulla oblongata
    The portion of the hindbrain that controls respiratory and blood pressure
  417. Meiosis
    A type of cell division (in diploid cells) that reduces the number of chromosomes by half. Meiosis usualy produces haploid gametes in organisms that undergo sexual reproduction. It consists of a single interphase (G1
  418. Melanin
    A pigment produced by melanocytes in teh bottom cell layer of the epidermis. Melanin production is increased on sun exposure and helps prevent cllular damage due to UV radiation.
  419. Memory cell
    A cell produced when a B cell is activated by antigen. Memory cells do not actively fight the current infection
  420. Meninges
    The protective
  421. Menopause
    The perio dof tim ein a woman's life when ovulation and menstruation cease. Menopause typically begins in the late 40s.
  422. Menstruation
    The first phase of the uterine (endometrial) cycle
  423. Mesoderm
    One of the three primary (embryonic) germ layers formed during gastrulation. Mesoderm ultimately forms 'middle' structures such as bones
  424. Metaphase
    The secon phase of mitosis. During metaphase chromosomes align at the center of the ell (the metaphase plate).
  425. Metaphase I
    The second phase of meiosis I. During metaphase I the paired homologous chromsomes (tetrads) align at the center of the cell (the metaphase plate).
  426. Metaphase II
    The second phase of meiosis II. Metaphase II is identical to mitotic metaphase
  427. MHC
    "Major Histocompatability complex
  428. Microfilament
    The cytoskeleton filaments with the smallest diameter. Microfilaments are composed of the contractile protein actin. They are dynamic filaments
  429. Microtubule
    The largest of the cytoplasmic filaments. Microtubules are composed of two types of protein
  430. Microvilli
    Microscopic outward folds of the cells lining the small intestine; microvilli serve to increase the surface area of the small intestine for absorption.
  431. Midbrain
    The portion of the brain responsible for visual and auditory startle reflexes.
  432. Milk letdown
    The release of milk from the mammary glands via contraction of ducts within the glands. Contraction is stimulated by oxytocin
  433. Missense mutation
    A point mutation in which a codon that specifies an amino acid is mutated into a codon that specifies a different amino acid.
  434. Mitochondrion
    An organelle surrounded by a double=membrane (two lipid bilayers) where ATP production takes place. The interior (matrix) is where PDC and the Krebs cycle occur
  435. Mitosis
    The phase of the cell cycle during which the replicated genome is divided. Mitosis has four phases (prophase
  436. Monocistronic mRNA
    mRNA that codes forsingle type of protein
  437. Monosaccharide
    The monomer of a carbohydrate. Monosaccharides have the general chemical formula CnH2nOn
  438. Morula
    A solid clump of cells resulting from cleavage in the early embryo. Because there is very little growth of these cells during cleavage
  439. Motor end plate
    The portion of the cell membrane at the neuromusclar junction; essentially the postsynaptic membrane at the synapse.
  440. Motor unit
    A motor neuron and all the all the skeletal muscle cells it innervates. Large motor units are typically found in large muscles (e.g.
  441. Motor unit recruitment
    A mechanism for increasing tension (contractile length) in a muscle by activating more motor units.
  442. mRNA
    Messenger RNA; the type of RNa that is read by a ribosome to synthesize protein.
  443. Mucocilliary escalator
    The layer of ciliated
  444. Mucosa
    The layer of epithelial tissue that lines body cavities in contact with the outside environment (respiratory
  445. Mullerian ducts
    Earlier embryonic ducts that can develop into femal internal genitalia in the absence of testosteron.
  446. Mullerian inhibiting factor (MIF)
    A substance secreted by embryonic testes that causes the regression of the Mullerian ducts.
  447. Multipolar neuron
    A neuron with a single axon and multiple dendrites; the most common type of neuron in the nervous system.
  448. Mutualism
    A form of symbiosis in which both organisms involved benefit from the association.
  449. Myelin
    An insulating layer of membranes wrapped around the axons of almost all neurons in the body. Myelin is essentially the plasma membranes of specialized cells; Schwann cells in the peripheral nervous system
  450. Myofiber
    A skeletal muscle cell
  451. Myofibril
    A string of sarcomeres with a skeletal muscle cell (hence smaller than myofiber). Each muscle cell contains hundreds of myofibirils.
  452. Myoglobin
    A globular protein found in muscle tissue that has the ability to bind oxygen. Myoglobin helps to store oxygen in the muscle for use in aerobic respiration (it does not move
  453. Myometrium
    The muscuar layer of the uterus. The myometrium is made of smooth muscles that retains its ability to divide in order to accomodate the massive size increases that occur during pregnancy. The myometrium is stimulated to contract during labor by the hormone oxytocin.
  454. Myosin
    One of the contractie proteins in muscle tissue. In skeletal and cardiac muscles
  455. Myosin light-chain kinase (MLCK)
    A kinase in smooth muscle cells activated by calmodulin the presence of Ca2+. As its name implies
  456. NADH
    The reduced form of NAD+ (nicotinamide adenine dinucleotide). This is the most common electron carrier in cellular respiration.
  457. Na+/K+ ATPase
    A protein found in the plasma membrane of all cells in the body that uses the energy of an ATP (hydrolyzes ATP) to move three Na+ ions out of the cell and two K+ ions into the cell
  458. Natural selection
    The mechanism described by Charles Darwin that drives evolution. Through mutation
  459. Nephron
    The function unit of the kidney. Each kidney has about a million nehprons; this is where blood filtration and subsequent modification of the filtrate occurs. The nephron empties into collecting ducts
  460. Neuron
    The basic functional and structural unit of the nervous system. The neuron is a highly specialized cell
  461. Neuromuscular junction
    The synapse between a motor neuron and a muscle cell. At the NMJ
  462. Neurotransmitter
    A chemical released by the axon of a neuron in response to an action potential that binds to receptors on a postsynaptic cell and causes that cell to either depolarize slightlly (EPSP) or hyperpolarize slightly (IPSP). Examples are acetylcholine
  463. Neuralation
    The formatino of the nervous system during weeks 5-8 of gestation. Neuralation begins when a section of the ectoderm invaginates and pinches off to form the neural groove
  464. Nociceptors
    Pain receptors. Nociceptors are found everywhere in the body except for the brain.
  465. Nodes of Ranvier
    Gaps in the myelin sheath of the axons of peripheral neruons. Action potentials can 'hump' from node to node
  466. Noncompetitive inhibitor
    An enzyme inhibitor that binds at a site other than the active sit of an enzyme (binds at an allosteric site). THis changes the three-dimensional shape of the enzyme such that it can no longer catalyze the reaction
  467. Nondisjunction
    The failure of homologous chromosomes or sister chromatids to separate properly during cell division. This could ocur during *anaphase I of meiosis (homologous chromosomes) [--> leaving 2 gametes w/ 2 copies and 2 gametes w/ no copies of chromosome]
  468. Nonsense mutation
    A point mutation in which a condon that specifies an amino acid is mutated into a stop (nonsense) codon.
  469. Norepinephrine
    The neurotransmitter used by the sympathetic division of the ANS at the postganglionic (organ-level ) synapse.
  470. Nuclear envelope
    The membrane surrounding the DNA in eukaryotic cells made of two lipid bilayers.
  471. Nuclear localization sequence
    A sequence of amino acids (usually basic) that directs a protein to the nuclear envelope
  472. Nuclear pore
    A protein channel in the nuclear envelope that llows the free passage of molecules smaller than 60 kD.
  473. Nucleolus
    A region within the nucleus where rRNA is transribed and ribosomes are partially assembled.
  474. Nucleoside
    A structure composed of a ribose molecule linked to one of the aromatic bases. In a deoxynucleoside
  475. Nucleosome
    A structure composed of two coils of DNA wrapped around an octet of histone proteins. The nucleosome is the primary form of packagin of eukaryotic DNA.
  476. Nucleotide
    A nucleoside with one or more phosphate gropus attached. Nucleoside triphosphates (NTPs) are the building blocks of RNA and are also used as energy molecules
  477. Nucleus
    An organelle bounded by a double membrane (double lipid bilayer) called the nuclear envelope. The nucleus contains the genome and is the site of replication and transcription.
  478. Linker DNA
    The string between beads of DNA on histones. They are also wrapped around a single histone
  479. Obligate aerobe
    An organism that requires oxygen to survive (aerobic metabolism only).
  480. Obligate anaerobe
    An organism that can only survive in the absence of oxygen (anaerobic metabolism); oxygen is toxic to obligate anaerobes.
  481. Okazaki fragments
    Small fragments of DNa produced on the lagging strand during DNa replication
  482. Olfactory receptors
    Chemoreceptors in the upper nasal cavity that respond to odo chemicals.
  483. Oncotic pressure
    The osmotic pressure in the blood vessels due only to plasma proteins (primarily albumin) --> causes water to rush back into capillaries at end.
  484. Oogonium
    A *precursor* cell that undergoes mitosis during fetal development to produce more oogonium. These cells are then activated to produce primary oocytes
  485. Operator
    A specific DNA nucleotide sequence where transcriptional regulatory proteins can bind.
  486. Operon
    A nucleotide sequence on DNA that contians three elemtns: a coding sequence for one or more enzymes
  487. Optic disk
    The 'blind spot' of the eye
  488. Optic nerve
    The nerve extending from the back of teh eyeball to teh brain that carries visual information. The ptic nerve is made up of the axons of the ganglion cells of the retina.
  489. Organ of Corti
    The structure in the cochlea of the inner ear made up of the basilar membrane
  490. Organogenesis
    The stage of human development during which the organs are formed. Organogenesis begins after gastrulation and is completed by the eight week of gestation.
  491. Orgasm
    A function of the reproductive system controlled by the sympathetic nervous system. In males
  492. Origin of replication
    The specific location on a DNa strand where replication begins.. Prokaryotes typically have a single origin of replication
  493. Osmosis
    The movement of water (the solvent) from its region of high concentration to its region of low concentration. NOte that the water concnetration gradient is opposite to the solute concentration gradient
  494. Osmotic pressure
    The force required to resist the movement of water by osmosis. Osmotic pressure is essentialy a measure of the concentration of a solution. A solution that is hyighly concnetrated has a strong tendency to draw water into itself
  495. Ossicles
    The three small bones found in the middle ear (the malleus
  496. Osteoblast
    A cell that produces bone.
  497. Osteoclast
    A phagocytic-like bone cell that breaks down bone matrix to release calcium and phosphate into the bloodstream.
  498. Osteocyte
    A mature
  499. Osteon
    The unit of combact bone
  500. Outer ear
    The portion of the ear consisting of the pinna and the external auditory canal. The outer ear is separated from the middle ear by the tympanic membrane (the eardrum).
  501. Oval window
    The membrane that separates the middle ear from the inner ear.
  502. Ovarian cycle
    The 28 days of the menstrual cycle as they apply to events in the ovary. The ovarian cycle has three subphases: the follicular phase
  503. Ovary
    The female primary sex organ. The ovary produces female gametes (ova) and secretes estrogen and progesterone.
  504. Ovulation
    The release of a secondary oocyte (along with some granulosa cells) from the ovary at the approximate midpoint of the menstrual cycle (typically around day 14). Ovulation is triggered by a surge in LH.
  505. Oxaloacetate
    A four-carbon molecule that binds with the two-carbon acetyl unit of acetyl-CoA to form citric acid in the first step of the Krebs cycle.
  506. Oxidation
    To attach oxygen
  507. Oxidative phosphorylation
    The oxidation of high-energy electron carriers (NADH and FADH2) coupled to the phosphorylation of ADP
  508. Oxytocin
    A hormone released by the posterior pituitary that stimulates uterine contractions during childbirth and milk ejection during breastfeeding.
  509. Pacemaker potential
    A self-initiating action potential that occurs in the conduction system of the heart and triggers action potentials (and thus contraction) in the cardiac muscle cells Tee pacemaker potential is triggered by the regular
  510. Pancreas
    An organs in the abdominal cavity with two roles. The first is an exocrine role: to produce digestive enzymes and bicarbonate
  511. Pancreatic duct
    The main duct of the pancreas. The pancreatic duct carries the exocrine secretions of the pancreas (enzymes and bicarbonate) to the small intestine (dueodenum).
  512. Parasite
    An organism that requires the aid of a host organism to survive
  513. Parasympathetic nervous system
    The division of the autonomic nervous system known as the 'resting and digesting' system. It causes a general decrease in body activities such as heart rate
  514. Parathyroid hormone (PTH)
    A hormone produced and secreted by the parathyroid glands that increases serum calcium levels. It targets the bones (stimulates osteoclasts)
  515. Parietal cells
    Cells found in gastric glands that secrete hydrochloric acid (for hydrolysis of ingested food) and gastric intrinsic factor (for absorption of vitamin B-12).
  516. Partial pressure
    The contribution of an individual gas to the total ppressure of a mixture of gases. Partial pressures are used to describe the amounts of the various gases carried in the bloodstream.
  517. Passive transport
    Movement across the membrane of a cell that does not require energy input from the cell. Passive transport relies on concentration gradients to provie the driving force for movement
  518. Penetrance
    The percentage of individuals with a particular genotype that actually displays the phenotype associated with the genotype.
  519. Penetration
    The second step in viral infection
  520. Pepsin
    A protein-digesting enzyme secreted by the chief cells of the gastric glands. Pepsin is secreted in its inactive form (pepsinogen) and is activated by gastric acid. It is unusual in that its pH optimum is around 1-2; most of these enzymes in the body function best at neutral pHs
  521. Peptide bond
    The bond formed between the carboxyl group of one amino acid and the amino group of another.
  522. Peptide hormone
    A hormone made of amino acids (in some cases just a single
  523. Peptidoglycan
    A complex polymer of sugars and amino acids; the substance from which bacterial ell walls are made.
  524. Perfusion
    The flow of blood through a tissue; ischeia is when there is no blood flow
  525. Peripheral chemoreceptors
    Receptors in the carotid arteries and the aorta that monitor blood pH to help regulate ventilation rate.
  526. Peripheral membrane protein
    A protein that is associated with the plasma membrane of a cell
  527. Periperal nervous system
    All parts of the nervous system except for the brain and spinal cord.
  528. Peripheral resistance
    The resistance to blood flow in the systemic circulation. Peripheral resistance increases if arteries constrict (diameter decreases)
  529. Periplasmic space
    The spac0e between the inner and outer cell membranes in Gram-negative bactera. The peptidoglycan cell wall is found in the periplasmic space
  530. Peristalsis
    A wave of contraction that sweeps along a muscular tube
  531. Peroxisome
    Small organelles that contain the hydrogen peroxide produced as a byproduct of lipid metabolism. Peroxisomes convert hydrogen peroxide to water and oxygen by way of the enzyme catalase.
  532. Phagocytosis
    The non-specific uptake of solid material by a cell accomplished by englufing the particle with plasma membrane and drawing it into the cell.
  533. Pharynx
    A passageway leading from behind the nasal cavity to the trachea. The pharynx is divided into three regions
  534. Phenotype
    The physical characterisitcs resulting from the genotype. Phenotypes are usually described as dominant or recessive.
  535. Phosphofructokinase
    The enzyme that catalyzes the phosphorylation of fructose-6-phosphate to form fructose-1-6-bisphosphate in the third step of glycolysis. This is the main regulatory step of glycolysis. PFK is feedback-inhibited by ATP.
  536. Phospholipid
    The primary membrane lipid. Phospholipids consist of a glycerol molecule esterified to two fatty acid chains and a phosphate molecule. Additional
  537. Photoreceptor
    A receptor that responds to light
  538. Phototroph
    An organism that utilizes light as its primary energy source.
  539. Pilus
    A long projection on a bacterial surface involved in an attachment
  540. Pinocytosis
    The non-specific uptake of liquid particles into a cell by invagination of the plasma membrane and subsequent 'pinching off' a small bit of the extracellular fluid.
  541. Placenta
    An organ that develops during pregnacy
  542. Placental villi
    Zygot-derived projections that extend into the endometrium of the uterus during pregnancy. Fetal capillaries grow into the placental villi
  543. Plaque
    A clear area in a lawn of bacteria. Plaques represent an area where bacteria are lysing (dying) and usually caused by a lytic virus.
  544. Plasma
    The liquid portion of blood; plasma contains water
  545. Plasma cell
    An activated B cell that is secreting antibody.
  546. Plasmid
    A small
  547. Platelets
    Extremely small pseudo-cells in the blood
  548. Pleiotropic gene
    A gene that has effects on several different characteristics.
  549. Pleura
    The membranes that line the surface of the lungs (visceral pleura) and the inside wall of the chest cavity (parietal pleura).
  550. Pleural pressure
    The pressure in the (theoretical) space between the lung surface and the inner wall of the chest cavity.
  551. Point mutation
    A type of mutation in DNa where a single base is substituted for another.
  552. Polar body
    A small cell with extremely little cytoplasm that results from the unequal cytoplasmic divsion of the primary (produces the first polar body) and the secondary (produces the second polary body) oocytes during meiosis (oogenesis). The polar bodies degenerate.
  553. Poly-A tail
    A string of several hundred adenine nucletodies added to the 3' end of the eukaryotic mRNA.
  554. Poycistronic mRNA
    mRna that codes for several different proteins by utliizing different reading frames
  555. Polysaccharides
    A molecule formed by joining many monosaccharides together. POlysaccharides are typically energy-storage molecules (glycogen in animals
  556. Polyspermy
    The fertilization of an oocyte by more than one sperm. This occurs in some animals
  557. Population
    A subset of a species consisting of members that mate and reproduce with one another.
  558. Pore
    A pathway through a plasma membrane that restrics passage based only on the size of the molecules. Pore are made from porin proteins.
  559. Portal systems
    A system of blood vessels where the blood passes from arteries to capillaries to veins
  560. Posterior pituitary gland
    Also known as the neurohyophysis
  561. Postganglionic neuron
    In the autonomic division of the PNS
  562. Potassium leak channel
    An ion channel specific for potassium found in the plasma membrane of all cells in the body. Leak channels are constitutively open and allow their specifi ion to move across the membrane according to its gadient. Potassium leak channels allow potassium to leave the cell.
  563. Power stroke
    The step in the sliding filament theory during which yosin undergoes a conformaitonal change to its low energy state
  564. Preganglionic neuron
    In the autonomic divison of the PNS
  565. Primary active transport
    Active transport that relies directly on the hydrolysis of ATP.
  566. Primary bronchi
    The first branches of the trachea. There are two primary bronchi
  567. Primary immune response
    The first encounter with an antigen
  568. Primary oocytes
    Diploid cells resulting from the activation of anoogoium; primary oocytes are ready to enter meiosis I. remember: cyte means ready to undergo meiosi
  569. Primary spermatocytes
    Diploid cells resultinf rom the activation of a spermatogoium; primary spermatocytes are ready to enter meiosis I. remember: cyte means ready to undergo meiosis.
  570. Primase
    An RNA polymerase that creates a primer (made of RNA) initiate DNa replication. DNA pol binds to the primer and elongates it.
  571. Productive cycle
    A life cycle of animal viruses in which the mature viral particles bud from the host cell
  572. Progesterone
    A steroid hormone produced by the corpus luteum in the ovary during the second half of the menstrual cycle Progesterone maintains and enhances the uterine lining for the possible implantation of a fertilized ovum. It is the primary hormone secreted during pregnancy.
  573. Prokaryote
    An organism that lacks a nucleus or any other memrane-bound organelles. All prokaytes belong to the Kingdom Monera (not protista!)
  574. Prolactin
    A hormone secreted by the anterior pituitary that tarets the mammary glands stimulating them to produce breastmilk.
  575. Proliferative phase
    The second phase of the uterine (endometrial) cycle
  576. Promoter
    The sequence of nucleotides on a chromosome that activates RNA polymerase so that transcription can take place. The promoter is found upstream of the start site
  577. Prophase
    The first phase of mitosis. During prophase the replicated chromosomes condense
  578. Prophase I
    The first phase of meiosis I. During prophase I the replicated chromosomes condense
  579. Prophase II
    The first phase of meiosis II. Prophase II is identical to mitotic prophase
  580. Proprioreceptor
    A receptor that responds to changes in body position
  581. Prostate
    A small gland encircling the male urethra just inferior to the bladder (only reproductive structure not paired). Its secretion contain nutrients and enzymes and account for approximately 35% of the ejaculate volume.
  582. Prosthetic group
    A non-protein
  583. Proteins
    Molecules made by connecting amino acids via peptide bonds. Proteins are synthesized (translated) by ribosomes
  584. Proximal convoluted tubuel
    The first portion of the nephron tubuel after the glomerulus. THe PCT is the site of most reabsorption; all filtered nutrients are reabsorbed here as well as most of the filtered water.
  585. P site
    Peptidyl-tRNA site; the stie on a ribosome where the growing peptide (attached to a tRNA) is found during translation.
  586. Ptyalin
    Salivary amylase
  587. Pulmonary artery
    The blood vessel that carries deoxygenated from the right ventricle of the heart to the lungs.
  588. Pulmonary circulation
    The flow of blood from the heart
  589. Pulmonary edema
    The collection of fluid in the alveoli
  590. Pulmonary vein
    One of several vessels that carry oxygenated blood from the lungs to the left atrium of the heart.
  591. Pupil
    A hole in the center of the iris of the eye that allows light to enter the eyeball. The diameter of pupil is controlled by the iris in response to the brightness of the light.
  592. Purine bases
    Aromatic bases found in DNA and RNA that are derived from purine. They have a double rightn structure and include adenine and guanine.
  593. Purkinje fibers
    The smallest (and final) fibers in the cardiac conduction system. The Purkinje fibers transmit the cardiac impulse to the ventricular muscle.
  594. Pyloric sphincter
    The valve that regulates the passage of chyme from the stomach into the small intestine.
  595. Pyrimidine bases
    Aromatic bases found in DNa and RNA that have a single-ring structure. They include cytosine
  596. Pyruvate dehydrogenase complex
    A group of three enzymes that decarboxylates pyruvate
  597. Pyruvic acid
    The product of glycolysis; 2 pyruvic acid (pyruvate) molecules are produced from a single glucose molecule. In the absence of oxygen
  598. Receptor-mediated endocytosis
    A highly specific cellular uptake mechanism. The molecule to be taken up must bind to cell surface receptor found in a clathrin-coated pit.
  599. Recessive
    The allele in a heterozygou genotype that is not expressed; the phenotype resulting from possession of two recessive alleles (homozygous recessive).
  600. Recombination frequency
    The RF value
  601. Rectum
    The final portion of the large intestine.
  602. Reduction
    To remove oxygen
  603. Reflex arc
    A relatively direct connection between a sensory neuron and a motor neuron that allows an extremely rapid response to a stimulus
  604. Relative refractory period
    The period of time following an action potential when it is possible
  605. Release factor
    A cytoplasmic protein that binds to a stop codon where it appears in the A-site of the ribosome. Release factors modify the peptidyl transferase activity of the ribosome
  606. Renal absorption
    The movement of a substance from the filtrate (in the renal tuble) bak into the bloodstream. Reabsorption reduces the amount of a substance in the urine.
  607. Renal tubule
    The portion of the nephron after the glomerulus and apsule; the region of the nephron where the filtrate is modified along its path to becoming urine.
  608. Renin
    An enzyme secreted by the juxtaglomerular cells when blood pressure decreases. Renin onverts angiotensinogen to angiotensin I.
  609. Replication
    The duplication of DNA
  610. Relication fork(s)
    The site(s) where the parental DNA double helix unwinds during replication.
  611. Replication bubbles
    Multiple sites of replication found on large
  612. Repolarization
    The return of membrane potential to normal resting values after a depolarization of hyperpolarization.
  613. Repressible enzyme
    An enzyme whose transcription can be stopped by an abundance of its product (as opposed to inducible enzymes). Usually part of anabolism of product.
  614. Repressor
    A regulatory protein that binds DNA at a specific nucleotide sequence (sometimes known as the operator) to prevent transcription of downstream genes.
  615. Residual volume
    The volume of air remaining in the lungs after a maximal forced exhalation
  616. Resolution
    A function the reproductive system (conrolled by the sympathetic nervous system) that returns the body to its normal resting state after sexual arousal and orgasm.
  617. Respiratory acidosis
    A drop in blood pH due to hypoventilation (too little breathing) and a resulting accumulation of Co2.
  618. Respiratory alkalosis
    Arise in blood pH due to hyperventilation (excessive breathing) and a resulting decrease in CO2.
  619. Resting membrane potential
    An electrical potential established across the plasma membrane of all cells by the Na+/K+ ATPase and the K+ leak channels. IN most cells
  620. Restriction endonuclease
    A bacterial enzyme that recognizes a specific DNA nucleotide sequence and that cuts the double helix at a specific site within the sequence.
  621. Retina
    The innermost layer of the eyeball. The retina is made up of a layer of photoreceptors
  622. Retinal
    A chemical derived from vitamin A found in the pigment proteins of the rod photoreceptors of the retina. Retinal changes conformation when it absorbs light
  623. Retrovirus
    A virus with an RNA genome (e.g. HIV) that undergoes a lysogenic life cycle in a host with a double stranded DNA genome. In order to integrate its genome with the host cell genome
  624. Reverse transcriptase
    An enzyme that polymerizes a strand of DNA by reading an RNA template (an RNA dependent DNa polymerase); used by retrovirus in order to integrate their genome with the host cell genome.
  625. Ribosome
    A structure made of two protein subunits and rRNA; this is the site of protein synthessis (translation) in a cell. Prokaryotic ribosomes (also known as 70S ribosomes) are smaller than eukaryotic ribosome (80S ribosomes). The S value refers to the sedimentation rate during centrifugation.
  626. RNA dependent RNA polymerase
    A viral enzyme that makes a strand of RNA by reading a strand of RNa . All prokaryotic and eukaryotic RNa polymerases are DNa dependent; they make a strand of RNa by reading a strand of DNA.
  627. RNA polymerase
    An enzyme that transcribes RNa. Prokaryotes have a single RNA pol
  628. Rods
    Photoreceptors in the retina of the eye that respond to dim light and provide us with black and white vision.
  629. Rough endoplasmic reticulum
    A large system of folded membranes within a eukaryotic cell that has ribosomes bound to it
  630. rRNA
    Ribosomal RNA; the type of RNA that associates with ribosomal proteins to make a functional ribosome. It is thought that the rRNA has the peptidyl transferase activity.
  631. Rule of addition
    A statistical rule stating that the probability of either of two indpendent (and mutually exclusive) events ocuring is the sum of their individual probabilities minus the probability of them both occuring together.
  632. Rule of multiplication
    A statistical rule stating that the probability of two independent events occuring together is the product of their individual probabilities.
  633. Saltatory conduction
    A rapid from of action potential conduction along the axon of a neuron in which the action potential appears to jump from nodde of Ranvier to node of Ranvier.
  634. Saprophyte
    An organism (such as a fungus) that feeds of dead plants and animals.
  635. Sarcolemma
    The plasma membrane of a muscle cell.
  636. Sarcomere
    The unit of muscle contraction. Sarcomeres are bounded by Z lins
  637. Sarcoplasmic reticulum
    The smooth ER of a muscle cell
  638. Schwann cell
    One of the two peripheral nervous system supporting (glial) cells. Schwann cells from he myelin sheath on axons of peripheral neurons.
  639. Sclera
    The white portion of teh tough outer layer of the eyeball
  640. Sebaceous gland
    Oil-forming glands found all over the body
  641. Seondary active transport
    Active transport that releies on an established concentration gradient
  642. Secondary immune response
    "A subsequent immune response to previously encountered antigen that results in antibody production and T cell activation. The secondary immune response is mediated by memory cells (produced during the primary immune respone) and is much faster and stronger than the rpimary response
  643. Secondary oocyte
    A haploid cell resulting from the first meiotic division of oogenesi (not that the cytoplasmic division in this case is unequal
  644. Secondary spermatocytes
    Haploid cells resulting from the first meiotic division of spermatogenesis. Secondary spermatocytes are ready to enter meiosis II.
  645. Secondary sex characteristics
    The set of adult characteristics that develop during puberty under the control of the sex steroids. In males the secondary sex characteristics include enlargement and maturation of the genitalia
  646. Second Law of Thermodynamics
    The entropy (disorder) of the universe (or system) tends to increase.
  647. Second messenger
    An intracellular chemical signal (such as cAMP ) that relays instructions from the cell surface to enzymes in the cytosol.
  648. Secretin
    A hormone secreted by the small intestine (duodenum) in response to low pH (e.g.
  649. Secretion
    (1) The secretion of useful substances from a cell
  650. Secretory phase
    The third phase of the uterin (endometrial) cycle
  651. Semen
    An alkaline
  652. Semicircular canals
    Three loop-like structures in the inner ear that contain sensory receptors to monitor balance.
  653. Semiconservative replication
    DNA replication in which each of the parental strands is read to make a complementary daughter strand
  654. Semilunar valves
    The valves in the heart that separate the ventricles from the arteries. The pulmonary semilunar valve separates the right ventricle from the pulmonary artery
  655. Seminal vesicles
    Paired glands found on the posterior external wall of the bladder in males. Their secretions contain an alkaline mucus and fructose
  656. Seminiferous tubules
    Small convoluted tubules in the testes where spermatogenesis takes place.
  657. Sertolli cells
    Cells that form the walls of the seminiferous tubules and help in spermatogenesis Sertoli cells are also called susenacular cells.
  658. Serum
    Plasma with the *clotting factors removed*. Serum is often used in diagnostic tests because it does not clot.
  659. Sex-linked rait
    A triat determined by a gen on either the X or Y chromosomes (the sex chromosomes).
  660. Shine-Dalgarno sequence
    The prokaryotic ribosome-binding site on mRNA
  661. Signal recognition particle (SRP)
    A cytoplasmic protein that recognizes the signal sequences of proteins destined to be translated at the rough ER. It binds first to the ribosome translating the protein with the signal sequence then to an SRP receptor on the rough ER>
  662. Signal sequence
    A short sequence of amino aids
  663. Signal transduction
    The intracellular process triggered by the binding of a ligand to its receptor on the cell surface. Typically this activates seond messenger pathways.
  664. Silent mutation
    A point mutation in which a codon that specifies an amino acid is mutated into a new codon that specifies the same amion acid.
  665. Simple diffsuion
    The movement of a hydrophobic molecule across the plasma membrane of cell
  666. Single strand binding proteins
    Proteins that bind to and stabilize the signle strands of DNA exposed when helicase unwinds the double helix in preparation for replication.
  667. Sinoatrial (SA) node
    A region of specialized cardiac muscle cells in the right atrium of the heart that initiate the impules of heart contraction; for this reason the SA node is knownas the 'pacemaker' of the heart.
  668. Sister chromatid
    Identical copies of a chromosome
  669. Skeletal muscle
    Muscle tissue that is attached to the bones. SKeletal muscle is striated multinucleate
  670. Siding filament theory
    The mechanism of contraction in skeletal and cardiac muscl cells. It is a series of four repeated steps: (1) myosin binds actin
  671. Slow block to polyspermy
    Also known as the cortical reaction
  672. Small intestine
    The regino of the digestive tract where virtually al digestion and absorption occur. It is subdivided into three regions: the duodenum
  673. Smooth Endoplasmic Reticulum
    A network of membranes inside eukarytoic cells invovled in lipid synthesis (steroid in gonads)
  674. Smooth muscle
    Muscle tissue found in the walls of hollow organs
  675. Soma
    The cell body of a neuron.
  676. Somatic nervous system
    The division of the peripheral nervous system that innervates and controls the skeletal muscles; also known as the voluntary nervous system.
  677. Spatial summation
    Integration by a postsynaptic neuron of inputs (EPSPs and IPSPs) from multiple sources.
  678. Spermatid
    A haploid but immature cell resulting from the second meiotic division f spermatogenesis. Spermatids undergo significant physical changes to become mature sperm (spermatozoa).
  679. Spermatogenesis
    Sperm production; occurs in human males on a daily basis from puberty until death. Spermatogenesis results in the production of four mature gametes (sperm) from a single precursor cell (spermatogonium). For maximum sperm viability
  680. Spermatogonium
    A diploid cell that can undergo mitosis to form more spermatogonium
  681. S phase
    The phase of the cell cycle during which the genome is replicated.
  682. Sphincter of Oddi
    The valvecontrolling release of bile and pancreatic juice into the bloodstream.
  683. Sphygmomanometer
    A blood pressure cuff
  684. Spirochete
    A bacterium having a spiral shape (plural = spirochetes)
  685. Spleen
    An abdominal organ that is considered part of the immune system. THe spleen has four functions: (1) it filters antigen from the blood (2) it is the site of B cell maturation
  686. Splicing
    One type of eukaryotic mRNA processing in which introns are removed from the primary transcript and exons are ligated together. SPlicing of transcripts can be different in different tissues.
  687. Spongy bone
    A looser
  688. Start site
    The location on a chromosome where transcription begins.
  689. Steroid hormone
    A hormone derived from cholesterol. Steroids are generally hydrophobic and can easily cross the plasma membrane of cells
  690. Stomach
    The portion of the digestive tract that stores and grinds food. Limited digestion occurs in the somach
  691. Stop codon
    A group of nucleotides that does not specify a particular amino acid
  692. Stroke volume
    The volume of blood pumped out the heart in a single contraction.
  693. Submucosa
    The layer of connective tissue directly under the mucosa of an open body cavity.
  694. Substrate(s)
    The reactants in an enzyme-catalyzed reaction. Substrate binds at the active site of an enzyme.
  695. Sudoriferous gland
    A sweat gland located in the dermis of the skin. Sweat consists of water and ions (including Na+ and urea) and is secreted with temperatures rise.
  696. Summation
    (1) The integration of input (EPSPs and IPSPs) from many presynaptic neruons by a single postsynaptic neuron
  697. Supercoiling
    A method of DNA protection utilized by prokaryotes in which their large circular chromosome is coiled upon itself.
  698. Surfactant
    An amphipathic molecule secreted by cells in the alveoli (type 2 alveolar cells) tha reducs surface tension on the inside of the alveolar walls. This prevents the alveoli from collapsing upon exhale and sticking together
  699. Sympathic nervous system
    "The division of the autonomic nervous system known as the ""fright or flight"" system. It causes a genera increase in body activities such as heart rate
  700. Symporter
    A carrier protein that transports two molecules across the plasma membrane in the same direction. For example
  701. Synapse
    A neuron-to-neuron
  702. Synapsis
    Pairing of homologus chromosomes in a diploid cell
  703. Synaptic cleft
    A microscopic space between the axon of one neuron and the cell body or dendrites of a secon neruon
  704. Syncytium
    A large multinucleate cell
  705. Syngergist
    Something that works together with another thing to augment the the second thing's activity. For example
  706. Synovial fluid
    A lubricating
  707. Systemic circulation
    The flow of blood from the heart
  708. Systole
    The period of time during which the ventricles of the heart are contracted.
  709. Systolic pressure
    The pressure measured in the arteries during contraction of the ventricles (during systole).
  710. T cell
    A type of lymphocyte. The major subtypes of T cells are the helper T cells (CD4) and the killer T cells (CD8
  711. Telencephalon
    The cerebral hemispheres.
  712. Telomere
    A specialized region at the ends of eukaryotic chromosmes that contains several repeats of a particular DNA sequence. These ends are maintained (in some cells) with the help of a special DNA poymerase called telomerase. In cells that lack telomerase
  713. Telophase
    The fourth (and final) phase of mitosis. During telophase the nuclear envelope reforms
  714. Telophase I
    The fourth of meiosis I. Telophase I is identical to mitotic telophase
  715. Telophase II
    The fourth and final phase of meiosis II. Telophase II is identical to mitotic telophase
  716. Temporal summation
    Summation by a postsynaptic cell of input (EPSPs or IPSPs) from a single source over time.
  717. Tendon
    Strong bands of connective tissue that connect skeletal muscle to bone.
  718. Testcross
    A genetic cross between an organism displaying a recessive phenotype (homozygous recessive) and an organism displaying a dominant phenotype (for whic the genotype is unknown)
  719. Testes
    The primary male sex organ. The testes are suspended outside the body cavity in the scrotum and have two functions (1) produce sperm
  720. Testosterone
    The primary androgen (male sex steroid). Testosterone is a steroid hormone produced and secreted by the interstitial cells of the testes. It triggers the development of secondary male sex characteristics during puberty (including spermatogenesis) and maintains those characteristics during adulthood.
  721. Tetanus
    A smooth sustained muscle contraction
  722. Tetrad
    A pair of replicated homologous chromosomes. Tetrads form during prophase I of meiosis so that homologous chromosomes can exchange DNA in a process known as 'crossing over.'
  723. Thalamus
    The central structure of the diencephalon of the brain. the thalamus acts as a relay station and major integrating area for sensory impulses.
  724. Thecal cells
    A layer of cells surroudning the granulosa cells of the follicles in an ovary. Thecal cells help produce the estrogen secreted from the follicle during the first phase of the ovarian cycle.
  725. Thermoreceptor
    A receptor that responds to changes in temperature.
  726. Theta replication
    DNA replication in prokaryotes
  727. Thick filament
    In skeletal and cardiac muscle tissue
  728. Thin filament
    In skeleta and cardiac muscle tissue
  729. Thrombus
    A blood clot that forms in an unbrokened blood vessel. Thrombi are dangerous they can break free and begin travelin in the bloodstream (become an embolus). Emboli ultimately become stuck in a small vessel and prevent adequate blood delivery to tissues beyond the sticking point
  730. Thymine
    One of the four aromatic bases found in DNA. Thymine is a pyrimidine; it pairs with adenine.
  731. Thymus
    An immune organ located near the heart. THe thymus is the site of T cell maturation and is larger in children and adolescents.
  732. Thyroid stimulating hormone (TSH)
    A tropic hormone produced by the anterior pituitary gland that targets the thyroid gland
  733. Thyroxine
    Also called thryoid hormone
  734. Tidal volume
    The volume of air inhaled and exhaled in a normla
  735. Tight junction
    Also called occluding junctions
  736. Tolerant anaerobe
    An organism that can survive in the presence of oxygen (oxygen is not toxic)
  737. Tonsils
    Paired masses of lymphatic tissue near the back of the throat that help trap inhaled or swallowed pathogens.
  738. Topoisomerase
    An enzyme that cuts one or both strands of DNa to relieve the excess tension caused by the unwinding of the helix by helicase during replication.
  739. Total lung capacity
    The maximal volume of air that the lungs can contain. Total lung capacity is the sum of the vital capacity and the residual volume
  740. Totipotent
    Having the ability to become anything; a zygote is totipotent.
  741. Trachea
    The main air tube leading into the respiratory system. The trachea is made of alternating rings of cartilage and connective tissue.
  742. Transcription
    The enzymatic process of reading a strand of DNA to produce a complemenetary strand of RNA
  743. Transduction
    The transfre by a lysogenic virus of a portion of a host cell genome to a new host.
  744. Transition mutation
    A point mutation in which a pyrimidine is susbstituted for a pyrimidine
  745. Translation
    The process of reading a strand of mRNA to synthesize protein. Protein translation takes place on a ribosome.
  746. Transmembrane domain
    The portion of an integral membrane protein that passes through the lipid bilayer.
  747. Transversion mutation
    A point mutation in which a pyrimidine is substitued for a purine
  748. tRNA
    Transfer RNA; the type of RNA that carries an amino acid from the cytoplasm to the ribosome for incorporation into a growing protein.
  749. tRNA loading
    The attachment of an amino acid to a tRNA (not that this a specific interaction). tRNa loading requires two high-energy phosphate bonds.
  750. Trophoblast
    The outer ring of cells of a blastocyst. The trophoblast takes part in the formation of the placenta.
  751. Tropic hormone
    A hormone tha tcontrols the release of another hormone.
  752. Tropomyosin
    A helical protein that winds around actin helices in skeletal and cardiac muscle cells to form the thin filament of the sarcomere. In the absence of Ca2+
  753. Troponin
    A globular protein that ssociated with tropomyosin as part of the thin filament of the sarcomere. Troponin binds Ca2+
  754. Trypsin
    The main protease secreted by the pancreas; trypsin is activated (from trypsinogen) by enterokinase
  755. T tubules
    Also called transverse tubules
  756. Tympanic membrane
    The membrane that separate the outer ear from the middle ear. The tympanic membrane is also known as the eardrum.
  757. Umbilical cord
    The cord that connects the embryo of a developing mammal to the placenta in the uterus of the mother. The umbilical cord contains fetal arteries (carry blood toward the placenta) and veins (carry blood away from the placenta). The umbilical vessels derive from the allantois
  758. Uniporter
    A carrier protein that transports a single molecule across the plasma membrane.
  759. Universal acceptor
    A person with blood type AB+. Because this person's red blood cells possess all of the typical blood surface proteins
  760. Universal donor
    A person with blood type O-. Because this person's red blood cells possess none of the typical blood suface proteins
  761. Upsteam
    Toward the 5' end of an Rna transcript (the 5' end of the DNA coding strand). The promoter and start sites are upstream.
  762. Uracil
    One of the four aromatic bases found in RNA. Uracil is pyrimidine; it pairs with adnenine.
  763. Urea
    A waste product of protein dbreakdown
  764. Ureters
    The tubes that carry urine from the kindeys to the bladder.
  765. Urethra
    The tube that carries urine from the bladder to the to outside of the body. In males it also carries semen and sperm during ejaculation.
  766. Urinary sphincter
    The valve that controls the release of urine from the bladder. It has an internal part made of smooth muscle (thus involuntary) and an external part made of skeletal muscle (thus voluntary).
  767. Uterine tubes
    Also called falopian tubes
  768. Uterus
    The muscular femal organ
  769. Vaccination
    The deliberate exposure of a person to an antigen in order to provoke the primary immune response and memory cell production. Typically the antigens are those normally associated with pathogens
  770. Vagal tone
    The constant inhibition provided to the heart by the vagus nerve. Vagal tone reduces the intrinsic firing rate of teh SA node from 120 beats/minute to around 80 beats/minute.
  771. Vagina
    The birth canal; the stretchy
  772. Vagus nerves
    Cranial nerve pair X. The vagus nerves are very large mixed nerves (They carry both sensory input and motor input) that innervate virtually every visceral organ. They are especially important in transmitting parasympathetic input to the heart and digestive smooth muscle.
  773. Vasa recta
    The capillaries that surround the tubules of the nephron. The vasa recta reclaims reabsorbed substances
  774. Vas deferens
    A thick muscular tube that connects the epididymis of the testes to the urethra. Muscular contractions of the vas deferns during ejaculation ehp propel the sperm outward. Severing of the vas deferens (vasectomy) results in sterility of the male.
  775. Vein
    A blood vessel that carries blood toward the heart chambers. Veins do not have muscular walls
  776. Vena cava
    One of two large vessels (superior and inferior) that return deoxygenated blood to the right atrium of the heart.
  777. Venous returns
    The amount of blood returned to heart by the vena cavae.
  778. Ventricle
    One of two large chambers in the heart. The ventricles receive blood from the atria and pump it out of the lungs of the heart. The right ventricle has thing walls and pumps deoxygenated blood to the lungs through the pulmonary artery. The left ventricle has thick walls and pumps deoxygenated blood the body through the aorta.
  779. Vestibular glands
    Paired glands near the posterior side of the vaginal that secrete an alkaline mucus upon sexual arousal. The mucus helps to reduce the acidity of the vagina (which could be harmful to sperm) and lubricates the vagina to facilitate penetration.
  780. Villi
    (Singular:villus). Folds of the intestinal mucosa that project into the lumen of the intestine; vili serve to increase the surface area of the intestine for absorption.
  781. Virus
    A nonliving
  782. Vital capacity
    The maximum amount of air that can be forcibly exhaled from the lungs after filling them to their maximum level
  783. Vitamin
    One of several different nutrietns that must be consumed in the diet
  784. Vitreous humor
    A thick
  785. Voltage-gated ion channel
    An ion channel that is oepend or closed based on the electrical potential across the plasma membrane. Once opened
  786. White matter
    Myelinated axons
  787. Wolffian ducts
    Early embryonic ducts that can develop into male internal genitalia under the proper stimulation (testosterone).
  788. Yolk sac
    An embryonic structure particularly important in egg-laying animals because it contains the yolk
  789. Z lines
    The ends of a saromere.
  790. Zona pellucida
    A thick
  791. Zygote
    A diploid cell formed by the fusion of two gametes during sexual reproduction.
  792. Zymogen
    An inactive precursor of an enzyme
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Matt's MCAT Flashcards