Biology Midterm (CH 1-9)

  1. What is the smallest unit of life?
    The smallest unit of life is the cell.
  2. What methods do biologists use to study cells?
    Microscopy and Cell Fractonation
  3. What is cell fractionation and describe the steps.
    Cell Fractionation: A technique that takes  cells apart and separates major organelles and other subcellular structures from one another

    The centrifuge spins test tubes holding  mixtures of disrupted cells at a series of  increasing speeds. At each speed, the  resulting force causes a subset of the cell  components to settle to the bottom of the  tube, forming a pellet.

    Lower speeds = pellet with larger components

    Higher speeds = pellet with smaller components
  4. Define resolution and magnification
    Resolution: A measure of the clarity; the  minimum distance two points can be  separated and still be distinguished as  separate points

    Magnification: The ratio of an object's image to its real size
  5. Describe the utility of light microscope
    The light microscope (LM) is used to magnify objects by using light.

    • ~The light is passed through the specimen
    • ~Light passes through  the lens
    • ~The lenses refract the light thus magnifying the specimen
    • ~The image is then projected into the eyepiece or camera
  6. What is an electron microscope?
    Focuses a beam of electrons through the  specimen or onto its surface
  7. Describe the two types of electron microscopes
    Scanning Electron Microscope (SEM): Show a 3D image of the surface of a specimen; Used for detailed study of topography of specimen

    Transmission Electron Microscope (TEM): Profiles a thin section of a specimen; Used to study internal structure of cells
  8. What are prokaryotic cells, and give examples?
    Prokaryotic Cells: DNA is concentrated in necleoid (a region that is not membrane-enclosed)

    Examples: Bacteria and Archaea
  9. What are eukaryotic cells and give examples?
    Eukaryotic Cells: Most of the DNA is in  nucleus (which is bounded by double membrane)

    Examples: Protists, Fungi, Animals, and Plants
  10. What are the basic features common to all cell types?
    Plasma Membrane - selective barrier bounding them

    Cytosol - semifluid, jelly-like substance inside plasma membrane in which subcellular components are suspended

    Chromosomes - Carry genes (DNA)

    Ribsomes- Tiny complexes that make proteins according to instructions from genes
  11. Describe the anatomy of a bacterial cell
    Fimbiae - Nucleoid - Ribosomes - Plasma Membrane - Cell Wall - Capsule - Flagella
  12. What is the surface to volume ratio?
    • [Surface Area : Volume]
    • [Surface Area / Volume]

    The plasma membrane functions to allow passage of just enough oxygen, nutrients, and wastes to service the entire cell. For each square micrometer, only a limited amount of a particular substance can cross per second.

    As a cell increases in size, its surface area  grows proportionately less than its volume.  Thus a smaller object has a greater ratio of  surface area to volume.
  13. Describe the plasma membrane and the major components of this membrane
    Selective barrier common to all cells

    The plasma membrane functions to allow  passage of just enough oxygen, nutrients,  and wastes to service the entire cell. For each square micrometer, only a limited amount of a particular substance can cross per second.
  14. Describe the nucleus.

    Include the nucleolus, chromosomes, and chromatin
    Contains most of the genes

    Nuclear Envelope encloses the nucleus, separating its contents from the cytoplasm

    Nucleolus: Mass inside nucleus where ribosomal RNA (rRNA) is synthesized from instructions in the DNA; Proteins imported from the cytoplasm are assembled with rRNA into small/large subunits of ribosomes

    Chromosomes: Structures that carry genetic information; Each contain one long DNA molecule and associated proteins (which help coil the DNA)

    Chromatin: The complex of DNA and proteins
  15. Describe ribosomes.Where are they found?
    Ribsomes: Complexes made of ribosomal RNA and protein that carry out protein synthesis

    Free ribsomes are suspended in the cytosol, Bound ribsomes are attached to the outside of the endoplasmic reticulum/nuclear envelope
  16. What is the endomembrane system and what does it include?
    System that carries out tasks in the cell  including: protein synthesis, protein transport (to membranes & organelles), metabolism & movement of lipids, and detox of poisons

    Includes: Nuclear Envelope, Endoplasmic Reticulum, Golgi Apparatus, Lysosomes, Various vesicles and vacuoles, and Plasma  Membrane
  17. Describe the endoplasmic reticulum
    Endoplasmic Reticulum (ER): Extensive network of membranes that accounts for more than half of the total membrane in many eukaryotic cells.

    Consists of tubules and sacs called cisternae.

    The ER membrane separates the ER lumen from the cytosol

    The ER membrane and nuclear envelope are continuous = the space between the two membranes of the envelope is continuous w/ the lumen of the ER

    Smooth ER and Rough ER
  18. Describe the function of the rough ER
    (Studded with ribsomes on the outer surface of the membrane)

    Makes secretory proteins and is membrane factory for the cell
  19. Describe the function of the smooth ER
    (Outer surface lacks ribsomes)

    Functions in diverse metabolic processes including: lipid synthesis, metabolism of carbs, poison/drug detox, and calcium ion storage
  20. Describe the structure and function of the Golgi
    Stacks of many flattened membranous sacs (cisternae); The membrane of each cisternae in a stack separates its internal space from the cytosol

    The membranes of cisternae located on  opposite sides of the stack differing in  thickness and molecular composition (cis and  trans face)

    Function: Modifies products of the endoplasmic reticulum, Manufactures some macromoleules
  21. What are lysosomes and what is their important function
    Membranous sac of hydrolytic enzymes that many eukaryotic cells use to digest macromolecules

    Function: Intracellular digestion in a variety  of circumstances and recycle the cell's own organic material (autophagy)
  22. What are vacuoles and name some organisms that possess specific types
    Vacoules: Large vesicles derived from the endoplasmic reticulum and Golgi apparatus; selective in transporting solutes

    Food Vacoules: Formed by phagocytosis

    Contractile Vacoules: Pump excess water out of the cell

    Central Vacoules: Develop by the coalescence of smaller vacoules; in mature plant cells; contains cell sap (which is plant's main storage of inorganic ions)
  23. What are the semiautonomous organelles?
    Mitochondria and Chloroplasts

    (autonomous organelles)
  24. Describe the mitochondria and what is its’ important function
    The sites of cellular respiration, the metabolic process that uses oxygen to drive the generation of ATP by extracting energy from sugars, fats, and other fuels
  25. Describe the chloroplast and what is its’ important function
    Found in plants and algae

    The sites of photosynthesis, converting solar energy to chemical energy by absorbing sunlight and using it to drive the synthesis of organic compounds such as sugars from CO2 and H2O
  26. Describe peroxisomes
    A specialized metabolic compartment bounded by a single membrane

    Contain enzymes that remove hydrogen atoms from various substrates and transfer them to oxygen, producing hydrogen peroxide as a by-product

    Many different functions

    • ~Use O to break fatty acids down into smaller molecules that are transported to mitochondria and used for fuel for cellular respiration
    • ~Those in the liver detoxify alcohol and other harmful compounds
    • ~Contains an enzyme that converts the poisonous H2O2 to H2O
    • ~Glyoxysomes in the fat-storing tissues of plant seeds contain enzymes that initiate the conversion of fatty acids to sugar
  27. What is a cell’s cytoskeleton?
    A network of fibers extending throughout the cytoplasm
  28. What are the three main proteins in cytoskeleton’s structure?
    • 1) Microtubules
    • 2) Microfilaments
    • 3) Intermediate Filaments
  29. What are motor proteins and what is their function within the cytoskeleton?
    Proteins that interact with cytoskeletal  elements and other cell components, producing movement of the whole cell or parts of the cell

    Inside the cell, vesicles and other organelle's use the motor protein "feet" to "walk" to their destinations along tracks provided by  cytoskeleton
  30. Describe the ECM of animal cells and its function
    ECM = Extracellular Matrix

    Made up of glycoproteins and other carb-containing molecules secreted by the cells

    Collagen is most abundant

    Can regulate a cell's behavior by communicating with a cell through integrins; Can influence the activity of genes in the nucleus
  31. What is collagen?
    Glycoprotein most abundant in the ECM of most animal cells

    Forms strong fibers outside the cells

    Accounts for about 40% of the total protein in the human body
  32. Describe plasmodesmata
    Channels that connect cells

    Cytosol passing through the plasmodesmata joins the internal chemical environments of adjacent cells. These connections unify most of the plant into one living continuum
  33. Describe tight junctions, desmosomes, and gap junctions
    Tight Junctions: Plasma membranes of   neighboring cells are very tightly pressed  against each other, bound together by specific proteins. Forming continuous seals around the cells. Establish a barrier that prevents leakage of extracellular fluid across a layer of epithelial cells.


    Desmosomes: Function like rivets, fastening cells together into strong sheets. Intermediate filaments made of sturdy keratin proteins anchor desmosomes in the cytoplasm. Attach muscle cells to each other in a muscle.

    Gap Junctions: Provide cytoplasmic channels from one cell to an adjacent cell and in this way are similar in their function to the plasmodesmata in plants. Consist of membrane proteins that surround a pore through which ions, sugars, amino acids, and other small molecules may pass. Necessary for communication between cells in many types of tissues.
  34. Define selective permeability
    Allows some substances to cross more easily than others
  35. What is a phospholipid and where is it found?
    An amphipathic molecule

    Most abundant lipid in most membranes
  36. What are amphipathic molecules?
    They have both a hydrophilic region and a hydrophobic region
  37. Define the fluid mosaic model
    The currently accepted model showing the arrangement of molecules in the plasma membrane
  38. Define saturated vs. unsaturated
    Saturated hydrocarbon tails pack together, increasing membrane viscosity

    Unsaturated hydrocarbon tails prevent packing, enhancing membrane fluidity
  39. Which scientists provided the necessary information for fluid mosaic model?
    In 1972, Singer and Nicolson proposed that the membrane is a mosaic of proteins dispersed and individually inserted into the phospholipid bilayer
  40. Which scientists proposed the sandwich model and the problems with this model?
    In 1935, H. Davson and J. Danielli proposed the sandwich model in which the phospholipid bilayer lies between two layers of globular proteins
  41. Describe the fluidity of the membranes
    Membranes are not static sheets of molecules locked in place. A membrane is held together by hydrophobic interactions (weaker than covalent). Most lipids and some of the proteins can shift laterally. Very rarely a lipid may flip-flop across the membrane switching from one phospholipid to the next
  42. How does temperature effect the fluidity of the membranes?
    A membrane remains fluid as temp decreases until phospholipids settle into closely packed arrangement and solidifies

    Temp at which a membrane solidifies depends on the type of lipids it's made of
  43. What are the two types of membrane proteins?
    Integral Proteins: Penetrate the hydrophobic interior of the lipid bilayer; Majority are transmembrane proteins

    Peripheral Proteins: Not embedded in the lipid bilayer at all; Appendages loosely bound to the surface of the membrane, often exposed to parts of integral proteins
  44. What are transmembrane proteins?
    Proteins that span the membrane
  45. Describe where microfilaments are located and their interaction in the plasma membrane.
    May be noncovalently bound to membrane proteins, a function that helps maintain cell shape and stabilizes the location of certain membrane proteins
  46. What are the functions of membrane proteins?
    • ~ Transport
    • ~ Enzymatic activity
    • ~ Signal transduction
    • ~ Cell-cell recognition
    • ~ Intercellular joining
    • ~ Attachment to the cytoskeleton and  extracellular matrix (ECM)
  47. What is meant by signal transduction, cell to cell recognition and intercellular joining?
    Signal Transduction: A membrane protein has a binding site with a specific shape that fits  the shape of the chemical messenger...The external messenger may cause the protein to change shape, allowing it to relay the message to the inside of the cell, usually binding to a cytoplasmic protein.

    Cell-to-Cell Recognition: Some glycoproteins serve as ID tags that are specifically recognized by membrane proteins of other cells. Usually short-lived.

    Intercellular Joining: Membrane proteins of adjacent cells may hook together in various kinds of junctions. More long lasting then cell-to-cell
  48. What is the difference between transport proteins and enzymatic activity proteins?
    Transport Proteins: The proteins that span the membrane may 1) provide a hydrophilic channel across the membrane that is selective, or, 2) shuttle a substance from one side to the other by changing shape

    Enzymatic Activity Proteins: The protein built into the membrane may be an enzyme with its active site exposed to substances in the adjacent solution. In some cases, several enzymes in a membrane are organized as a team that carry out sequential steps of a metabolic pathway.
  49. What are the two main types of membrane carbohydrates?
    Short, branched chains of fewer than 15 sugar units

    Glycolipids: Molecules covalently bonded to lipids

    Glycoproteins: Molecules covalently bonded to proteins (most are glycoproteins)
  50. Describe the hydrophilic and hydrophobic regions and what can penetrate the bilayer
    • Nonpolar molecules are hydrophobic, so they can dissolve in the lipid bilayer of the  membrane and cross it easily, without the aid of membrane proteins.
    •       Ex: O2 and CO2

    • Ions and Polar molecules are hydrophilic, so the hydrophobic interior of the membrane impedes direct passage through the membrane
    •       Ex: Glucose (& other sugars) and even H2O pass only slowly through a lipid bilayer
  51. Name the types of transport proteins and differentiate between carrier and channel proteins
    Channel Proteins: Function by having a hydrophilic channel that certain molecules or  atomic ions use as a tunnel through the membrane

    Carrier Proteins: Hold onto their passengers and change shape in a way that shuttles them across the membrane
  52. Define passive transport.
    The diffusion of a substance across a biological membrane
  53. Define active transport
    The pumping of a solute across a membrane against its gradient, requiring a cell's energy to do the work
  54. Define diffusion and give some examples of simple diffusion
    Diffusion: The movement of particles of any substance so that they spread out into the available space

    Example: Cellular Respiration
  55. Define osmosis and give an example
    The diffusion of free water across a selectively permeable membrane, whether artificial or cellular
  56. What is tonicity and what are the three osmotic possibilities?
    Tonicity: The ability of a surrounding solution to cause a cell to gain or lose water; Depends on its concentration of solutes that cannot cross the membrane relative to that inside the cell

    Hydrotonic: Water will enter faster than it leaves

    Isotonic: No net movement of water across the plasma membrane; Water diffuses but at the same rate in both directions

    Hypertonic: Water leaves faster than it enters
  57. Explain what would happen to a plant cell in a hypertonic environment
    Plant cells are turgid (=firm) and healthiest in hypertonic environments

    The uptake of water is eventually balanced by the wall pushing back on the cell

    Hypotonic (normal) ~ Isotonic (limp) ~ Hypertonic (plasmolyzed)
  58. Explain what would happen to an animal cell in a hypertonic environment
    Animal cells would lose water, shrivel, and probably die.

    Hypotonic (swell/burst) ~ Isotonic (normal) ~ Hypertonic (shrivel/die)
  59. Differentiate between turgidity and plasmolysis and which cells does it occur
    Turgidity: Turgid means very firm; the healthy state for most plant cells

    Plasmolysis: Phenomenon when a plants plasma membrane pulls away from the cell wall at multiple places as the plant shrivels  due to loss of water; Can cause plant to wilt, then plant death
  60. How does a paramecium adapt to a hypotonic environment?
    It has a plasma membrane that is much less permeable to water than the membranes of most other cells, which only slows the continual uptake of water. It doesn't burst because of its contractile vacuole, which acts as a bilge pump, forcing water out as quick as it enters by osmosis
  61. How does water and hydrophilic substances cross the membrane?
    Facilitated Diffusion
  62. What is facilitated diffusion?
    Phenomenon where polar molecules and ions impeded by the lipid bilayer of the membrane diffuse passively with the help of transport proteins that span the membrane
  63. Describe the sodium-potassium pump, and when would an organism use this pump
    Transport system that exchanges Na+ for K+ across the plasma membrane of animal cells
  64. Differentiate between active and passive transport
    Passive transport does not require work, while active transport does.

    Diffuse vs Pump
  65. Explain the electrochemical gradient
    The combination of an electrical force and a chemical force acting on an ion

    Because the inside of a cell is negative compared with the outside, the membrane potential favors the passive transport of cations into the cell and anions out of the cell, thus two forces drive the diffusion of ions across a membrane
  66. Describe the electrogenic pump better known as the proton pump
    The proton pump is the main electrogenic pump of plants, fungi, and bacteria (sodium-potassium pump the electrogenic pump of animals)

    Actively transports protons out of the cell, which transfers positive charge from the cytoplasm to the extracellular solution.

    Elecrogenic pumps help store energy that can be tapped for cellular work
  67. What is cotransport?
    Mechanism in which a transport protein can couple the "downhill" diffusion of the solute to the "uphill" transport of a second substance against its own concentration gradient
  68. Describe the activity of the protein called the sucrose-H+ cotransporter
    Sucrose-H+ cotransporter is able to use the diffusion of H+ down its electrochemical  gradient into the cell to drive the uptake of sucrose
  69. Describe Exocytosis and give some examples
    Exocytosis: Process where the cell secretes certain molecules by the fusion of vesicles with the plasma membrane

    • Examples:
    • Cells in the pancreas that make insulin secrete it into the extracellular fluid by exocytosis

    Nerve cells use exocytosis to release neurotransmitters that signal other neurons or muscle cells

    • When plant cells are making walls exocytosis
    • delivers proteins and carbs from the Golgi vesicles to the outside of the cell
  70. Describe endocytosis, the types of endocytosis and give several examples
    Endocytosis: The cell takes in molecules and particulate matter by forming new vesicles from the plasma membrane; The events look like a reverse exocytosis

    Phagocytosis: A cell engulfs a particle by extending pseudopodia around it and packaging it within a food vacoule

    Pinocytosis: A cell continually "gulps" droplets of extracellular fluid into tiny  vesicles, formed by infoldings of the plasma membrane. The cell obtains molecules dissolved in the droplets.

    Receptor-Mediated Endocytosis: A specialized type of pinocytosis that enables the cell to acquire bulk quantities of specific substances, even though those substances may not be very concentrated in the extracellular fluid. Embedded in the plasma membrane are proteins with receptor sites exposed to the extracellular fluid
  71. What is metabolism?
    The totality of an organism's chemical reactions; Emergent property of life that arises from orderly interactions between molecules
  72. Define Catabolic pathways
    Metabolic pathway that releases energy by breaking down complex molecules to simpler compounds

    Ex: Cellular Respiration
  73. Describe Anabolic pathways
    Metabolic pathway that consumes energy to build complicated molecules from simpler ones

    Also called, biosynthetic pathways

    Ex: Synthesis of protein from amino acid
  74. Differentiate between kinetic energy and potential energy
    Kinetic Energy: The relative motion of an object

    Potential Energy: Energy that matter possesses because of its location or structure
  75. Describe thermodynamics
    The study of energy transformations that occur in a collection of matter
  76. What is the first law of thermodynamics
    The energy of the universe is constant

    "Energy can be transferred and transformed, but it cannot be created or destroyed"
  77. What is the second law of thermodynamics?
    There is an unstoppabletrend toward randomization of the universe as a whole

    "Every energy transfer or transformation increases the entropy of the universe"
  78. What is a negative ^G indicate?
    A negative ^G indicates that ^H and T^S are tallied.

    • ^H must be negative or T^S must be positive, or both
    • ^G = ^H - T^S   
    • (G= change in free energy, H = change in enthalpy, S = change in entropy, T = absolute temperature in Kelvin)
  79. Define Exergonic reactions
    • Releases free energy
    • ^G is negative
    • Spontaneous
  80. Define Endergonic reactions
    • Absorbs free energy
    • ^G is positive 
    • Nonspontaneous
  81. What are the three main kinds of work in a cell?
    Chemical Work: The pushing of endergonic reactions that would not occur spontaneously

    Transport Work: The pumping of substances across membranes against the direction of  spontaneous movement

    Mechanical Work: The contraction of muscle cells
  82. Define the structure of ATP
    Adenosine Triphosphate (ATP)

    Contains: sugar ribose with nitrogenous base adenine and a chain of 3 phosphate groups bonded to it

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  83. What occurs during the hydrolysis of ATP?
    The release of free energy generates heat.

    The cell's proteins harness the energy released to perform the three types of cellular work
  84. What is the term energy coupling and give an example
    The use of an exergonic process to drive an endergonic one

    Ex: Formation of glutamine from glutamic acid and ammonia
  85. What is phosphorylation?
    Transferring a phosphate group to some other molecule, such as a reactant
  86. What are catalysts?
    A chemical agent that speeds up a reaction without being consumed by the reaction
  87. What is the effect of enzymes on the reaction rate?
    Enzymes can only hasten reactions that would eventually happen anyway
  88. Describe the active site, substrate, induced fit, and products in an enzyme catalyzed reaction
    Active Site: A pocket or groove on the surface of the enzyme where catalysis occurs; The restrictive region of the enzyme molecule that actually binds to the substrate

    Substrate: The reactant an enzyme acts on; Bound with an enzyme, forms enzyme-substrate complex; The enzyme converts the substrate to the product of the reaction

    Induced Fit: Active site fits even more snugly around substrate; Brings chemical groups of the active site into positions that enhance their ability to catalyze the chemical reaction
  89. The active site of an enzyme can lower an EA barrier by four ways. Name the four ways...
    • 1) Orienting substrates correctly
    • 2) Straining substrate bonds
    • 3) Providing a favorable microenvironment
    • 4) Covalently bonding to the substrate
  90. Enzyme activity can be affected a number of ways. Name the different ways...
    • ~ Temperature and pH
    • ~ Cofactors
    • ~ Enzyme Inhibitors
  91. What is meant by an enzyme’s optimal temperature and pH?

    Give some examples
    The optimal temperature allows the greatest number of molecular collisions and the fastest conversion of the reactants to product molecules.

    The optimal pH is where the enzyme is most active; Fall in the range of pH 6-8 (there are exception)
  92. What is a cofactor and give examples
    Nonprotein helpers required by enzymes to aid in catalytic activity; May be bound tightly to the enzyme as permanent residents or they may bind loosely and reversibly along  the substrate

    Coenzyme: Cofactor that is an organic molecule

    Ex: Vitamins important in nutrition
  93. What is a coenzyme and give examples
    Coenzyme: Cofactor that is an organic molecule

    Ex: Vitamins important in nutrition
  94. Differentiate between competitive and noncompetitive inhibitors
    • Competitive Inhibitors: Reversible inhibitors that resemble the normal substrate molecule and compete for admission into the active site; Reduce the productivity of enzymes by blocking substrates from entering active sites
    • Noncompetitive Inhibitors:  Do not directly compete with the substrate to bind the enzyme at the active site; Impede enzymatic  reactions by binding to another part of the enzyme; Causes the enzyme molecule to change its shape in such a way the active site become less effective at catalyzing the conversion of substrate to product
  95. Explain allosteric regulation
    Any case in which a protein's function at one site is affected by the binding of a regulatory molecule to a separate site

    May result in either inhibition or stimulation of an enzyme's activity
  96. Describe feedback inhibition
    A metabolic pathway is halted by the inhibitory binding of its end product to an enzyme that acts early in the pathway; Results when ATP allosterically inhibits an enzyme in an ATP-generating pathway
Card Set
Biology Midterm (CH 1-9)
Campbell Biology 10th Edition CH 1-9