A&P ch 3

  1. cell theory
    • cell is the smallest structural and functional living unit
    • organismal functions depend on individual and collective cell functions
    • biochemical activities of cells are dictated by their specific sucellular structures
    • continuity of life has a cellular basis
  2. 3 basic parts of human cells
    • plasma membrane
    • cytoplasm
    • nucleus
  3. plasma membrane
    • bimolecular layer of lipids and proteins in constantly changing fluid mosaic
    • dynamic role in cell activity
    • separates intracellular fluid (ICF) from extracellular fluid (ECF) - interstitial fluid (IF) = ECF
    • membrane lipids
  4. membrane lipids
    • phospholipids
    • glycolipids
    • cholesterol
  5. membrane proteins
    • integral proteins
    • peripheral proteins
  6. integral proteins and function
    • firmly inserted into membrane (most transmembrane)
    • transport proteins, enzymes or receptors
  7. peripheral proteins and function
    • loosely attached to integral proteins
    • include filaments on intracellular surface and glycoproteins on extracellular surface
    • enzymes, motor proteins, cell-to-cell links, provide support on intracellular surface, and form part of glycocalyx
  8. membrane protein functions (6)
    • transport
    • receptors for signal transduction
    • attachment to cytoskeleton and extracellular matrix
    • enzymatic activity
    • intercellular joining
    • cell-cell recognition
  9. membrane junctions
    • gap junction - pores that allow small molecules to pass from cell to cell
    • tight junction - prevent fluids and most molecules from moving between cells
    • desmosome - "rivets" that anchor cells together
  10. membrane transport
    • passive processes - no cellular energy (ATP) required; substance moves down its concentration gradient
    • active processes - energy required; occurs only in living cell membranes
  11. passive processes (4)
    • simple diffusion
    • carrier mediated diffusion
    • channel mediated diffusion
    • osmosis
  12. simple diffusion
    movement of fat soluble molecules directly through phospholipid bilayer down concentration gradient
  13. carrier mediated facilitated diffusion
    • protein carrier specific for one chemical
    • binding of substrate causes shape change in transport protein
    • sugars, amino acids are transported
  14. channel mediated facilitated diffusion
    • channel protein
    • mostly ions selected based on size and charge
  15. osmosis
    diffusion of solvent (usually water) through a specific channel protein or through the lipid bilayer
  16. tonicity
    ability of a solution to cause a cell to shrink or swell
  17. isotonic
    solution and cytosol have same concentration
  18. hypertonic
    • solution has greater concentration than cytosol
    • water moves out of cell
  19. hypotonic
    • solution has less concentration than cytosol
    • water moves into cell
  20. active transport
    • requires carrier proteins (solute pumps)
    • moves solutes against concentration gradient
    • 2 types - primary and secondary
  21. primary active transport
    • uses ATP
    • energy from hydrolysis of ATP causes shape change in transport protein so that bound solutes (ions) are "pumped" across the membrane
  22. sodium-potassium pump
    • located in all plasma membranes
    • involved in both primary and secondary transport
    • maintains electrochemical gradients essential for functions of muscle and nerve tissues
  23. secondary active transport
    • depends on an ion gradient created by primary active transport
    • energy stored in ionic gradients is used indirectly to drive transport of other solutes
    • cotransport - always transports more than one substance at a time; symport - substances transported in same direction; antiport - substances transported in opposite directions
  24. vesicular transport
    • forms of active transport
    • transport of large particles, macromolecules, and fluids across plasma membranes
    • requires energy
  25. functions of vesicular transport
    • exocytosis - transport out of cell
    • endocytosis - transport into cell
    • transcytosis - transport into, across, then out of cell
    • substance trafficking - transport from one area or organelle in cell to another
  26. phagocytosis
    transports larger molecules or substances by engulfing/"eating" them
  27. pinocytosis
    transports fluids
  28. receptor mediated endocytosis
    hormone and cholesterol uptake
  29. membrane potential
    the separation of oppositely charged particles (ions) across a membrane creates a membrane potential (potential energy measured as voltage)
  30. resting membrane potential (RMP)
    • voltage measured in resting state in all cells
    • ranges from 50-100 mV
    • results from diffusion and active transport of ions (mostly K+)
  31. generation and maintenance of RMP (6)
    • the Na+-K+ pump (sodium potassium pump) continually ejects Na+ from cell and carries K+ back in (3Na+ : 2K+)
    • some K+ continually diffuses down its concentration gradient out of cell through K+ leakage channels
    • membrane interior becomes negative (relative to exterior) because of lg anions trapped inside cell
    • electrochemical gradient begins to attract K+ back into cell
    • RMP is established at the point where the electrical gradient balances the K+ concentration gradient
    • a steady state is maintained because the rate of active transport is equal to and depends on the rate of Na+ diffusion into the cell
  32. cell-environment interactions
    involves glycoproteins and proteins of glycocalyx - cell adhesion molecules (CAMs) and membrane receptors
  33. cell adhesion molecules (CAMs)
    • anchor ells to extracellular matrix or to each other
    • assist in movement of cells past one another
    • CAMs of blood vessel lining attract white blood cells to injured or infected areas
    • stimulate synthesis or degradation of adhesive membrane junctions
    • transmit intracellular signals to direct cell migration, proliferation and specialization
  34. membrane receptors
    • contact signaling - touching and recognition of cells eg. normal development and immunity
    • chemical signaling - interaction between receptors and ligands (neurotransmitters, hormones and paracrines) to alter activity of cell proteins (eg. enzymes or chemically gated ion channels)
    • G protein-linked receptors - ligand binding activates a G protein, affecting an ion channel or enzyme or causing the release of an internal second messenger, such as cyclic AMP
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  35. cytoplasm
    • located between plasma membrane and nucleus
    • contains - cytosol (water with solutes), cytoplasmic organelles, and inclusions (granules of glycogen or pigments, lipid droplets, vacuoles and crystals)
  36. cytoplasmic organelles
    • 2 types -
    • membranous - mitochondria, peroxisomes, lysosomes, endoplasmic reticulum, golgi apparatus
    • nonmembranous - cytoskeleton, centrioles, ribosomes
  37. mitochondria
    • double-membrane structure with shelflike cristae
    • provide most of cell's ATP via aerobic cellular respiration
    • contain their own DNA and RNA
  38. ribosomes
    • granules containing protein and rRNA
    • site of protein synthesis
    • free ribosomes synthesize soluble proteins
    • membrane-bound ribosomes (on rough ER) synthesize proteins to be incorporated into membranes or exported from the cell
  39. ER
    • interconnected tubes and parallel membranes enclosing cisternae
    • continuous with nuclear membrane
    • 2 types - rough and smooth
  40. rough ER
    • external surface studded with ribosomes
    • manufactures all secreted proteins
    • synthesizes membrane integral proteins and phospholipids
  41. smooth ER
    • tubules arranged in a looping network
    • enzyme (integral protein) functions:
    • - in the liver - lipid and cholesterol metabolism, breakdown of glycogen, and along with kidneys, detox of drugs, pesticides and carcinogens
    • - synthesis of steroid-based hormones
    • - in intestinal cells - absorption, synthesis, and transport of fats
    • - in skeletal and cardiac muscle - storage and release of calcium
  42. golgi apparatus
    • stacked and flattened membranous sacs
    • modifies, concentrates, and packages proteins and lipids
    • transport vessels from ER fuse with convex cis face of Golgi
    • proteins then pass through Golgi to trans face
    • secretory vesicles leave trans face of Golgi stack and move to designated parts of cell
  43. lysosomes
    • spherical membranous bags containing digestive enzymes (acid hydrolases)
    • digest ingested bacteria, viruses, and toxins
    • degrade nonfunctional organelles
    • break down and release glycogen
    • break down bone to release Ca2+
    • destroy cells in injured or nonuseful tissue (autolysis)
  44. endomembrane system
    • produces, stores and export biological molecules
    • degrades potentially harmful substances
  45. peroxisomes
    • membranous sacs containing powerful oxidases and catalases
    • detoxify harmful or toxic substances
    • neutralize dangerous free radicals (highly reactive chemicals with unpaired electrons)
  46. cytoskeleton
    • elaborate series of rods throughout cytosol
    • microtubules
    • microfilaments
    • intermediate filaments
  47. microfilaments
    • dynamic actin strands attached to cytoplasmic side of plasma membrane
    • involved in cell motility, change in shape, endocytosis and exocytosis
  48. intermediate filaments
    • tough, insoluble ropelike protein fibers
    • resist pulling forces on the cell and attach to desmosomes
  49. microtubules
    • dynamic hollow tubes
    • most radiate from centrosome
    • determine overall shape of cell and distribution of organelles
  50. motor molecules
    • protein complexes that func tion in motility (eg movement of organelles and contraction)
    • powered by ATP
  51. centrosome
    • cell center near nucleus
    • generates microtubules; organizes mitotic spindle
    • contains centrioles: small tube formed by microtubules
  52. cellular extensions
    • cilia and flagella - whiplike, motile extensions on surgaces of certain cells, contain microtubules and motor molecules, cilia move substances across cell surfaces, longer flagella propel whole cells
    • microvilli - fingerlike extensions of plasma membrane, increase surface area for absorption, core of actin filaments for stiffening
  53. nucleus
    • genetic library with blueprints for nearly all cellular proteins
    • responds to signals and ditates kinds and amounts of proteins to be synthesized
    • most cells are uninucleate
    • red blood cells are anucleate
    • skeletal muscle cells, bone destruction cells, and some liver cells are multinucleate
  54. nuclear envelope
    • double-membrane barrier containing pores
    • outer layer is continuous with rough ER and bears ribosomes
    • inner lining (nuclear lamina) maintains shape of nucleus
    • pore complex regulates transport of lg molecules into and out of nucleus
  55. nucleoli
    • dark-staining spherical bodies within nucleus
    • involved in rRNA synthesis and ribosome subunit assembly
  56. chromatin
    • thread-like strands of DNA, histone proteins and RNA
    • arranged in fundamental units called nucleosomes
    • condense into barlike bodies called chromosomes when the cell starts to divide
  57. cell cycle
    • defines changes from formation of the cell until it reproduces
    • interphase (G1, S, G2)
    • cell division
    • -prophase
    • -metaphase
    • -anaphase
    • -telophase
  58. interphase
    • period from cell formation to cell division
    • nuclear material called chromatin
    • 4 subphases
    • - G1 vigorous growth and metabolism
    • - G0 gap phase in cells that permanently cease dividing
    • - S DNA replication
    • - G2 preparation for division
  59. DNA replication
    • DNA helices begin unwinding from the nucleosomes
    • helicase untwists the double helix and exposes complementary chains
    • the Y-shaped site of replication is the replication fork
    • each nucleotide strand serves as a template for building a new complementary strand
    • DNA polymerase works in one direction, continuous leading strand is synthesized, discontinuous lagging strand is synthesized in segments, DNA ligase splices together short segments of discontinuous strand
  60. mitotic phase of cell cycle
    • essential for body growth and tissue repair
    • doesn't occur in most mature cells of nervous tissue, dkeletal muscle, and cardiac muscle
  61. 2 distinct events of cell division
    • mitosis
    • cytokinesis
  62. prophase
    • chromosomes become visible, each with two chromatids joined at a centromere
    • centrosomes separate and migrate toward opposite poles
    • mitotic spindles and asters form
    • nuclear envelope fragments
    • kinetochore microtubules attach to kinetochore of centromeres and draw them toward the equator of the cell
    • polar microtubules assist in forcing the poles apart
  63. metaphase
    • centromeres of chromosomes are aligned at the equator
    • this plane midway between the poles is called the metaphase plate
  64. anaphase
    • shortest phase
    • centromeres of chromosomes split dimultaneously- each chromatid now becomes a chromosome
    • chromosomes (V shaped) are pulled toward poles by motor proteins of kinetochores
    • polar microtubules continue forcing the poles apart
  65. telophase
    • begins when chomosome movement stops
    • the two sets of chromosomes uncoil to form chromatin
    • new nuclear membrane forms around each chromatin mass
    • nucleoli reappear
    • spindle disappears
  66. cytokinesis
    • bigins during late anaphase
    • rign of actin microfilaments contracts to form a cleavage furrow
    • two daughter cells are pinched apart, each containing a nucleus identical to the original
  67. control of cell division
    "go" signals - critical volume of cell when membrane is inadequate for exchange; chemicals

    "stop" signals - cantact inhibition; growth-inhibiting factors produced by repressor genes
  68. mRNA
    carries instructions for building a polypeptide, from gene in DNA to ribosomes in cytoplasm
  69. rRNA
    structural component of ribosomes that, along with tRNA, helps translate message from mRNA
  70. tRNA
    bind to amino acids and pair with bases of codons of mRNA at ribosome to begin process of protein sythesis
  71. transcription factor
    • loosens histones from DNA in area to be transcribed
    • binds to promoter, a DNA sequence specifyin g start site of gene to be transcribed
    • mediates the binding of RNA polymerase to promoter
  72. RNA polymerase
    • enzyme that oversees synthesis of mRNA
    • unwinds DNA template
    • adds complementary RNA nucleotides on DNA template and joins them together
    • stops when it reaches termination signal
    • mRNA pulls off the DNA template, is further processed by enzymes, and enters cytosol
  73. translation
    • mRNA attaches to a small ribosomal subunit that moves along the mRNA to the start codon
    • lg ribosomal unit attaches, forming a functional ribosome
    • anticodon of a rRNA binds to its complementary codon and adds its amino acid to the forming protein chain
    • new amino acids are added by other tRNAs as ribosome moves along rRNA, until stop codon is reached
  74. role of rough ER in protein synthesis
    • mRNA-ribosome complex is directed to rough ER by a signal-recognition particle (SRP)
    • forming protein enters the ER
    • sugar groups may be added to the protein, and its shape may be altered
    • protein is enclosed in a vesicle for transport ot Golgi
Card Set
A&P ch 3