ch5 bio

  1. general stucture of membranes is known as
    fluid mosaic model
  2. like a "lake" in which is variety of proteins "float"
    phospholipid bilayer
  3. maintain a bilayer organization spontaneously helps membranes fuse during phagocytosis, vesicale formation, etc
  4. phospholipids vary fatty acid chain length, degree of saturation, phosphate groups
    membranes may be up to 25 percent cholesterol
  5. membranes contain proteins, the number of proteins varies with cell function
    some membrane proteins extend across the lipid bilayer ith hydrophobic and heydrophilic regions or domains
  6. the proteins and lipids in the membrane are independent and only interact noncovalently
  7. spand the bilayer, hydrophilic ends protrude on either side
    integral membrane proteins
  8. dont penetrate teh bilayer
    peripheral membrane proteins
  9. may have different domains on either side of the membrane
    transmembrane proteins
  10. the two sides of the membrane can have very different properties
    some membrane proteins can move freely within teh bilayer, while some are anchored to a specific region
  11. some membrane proteins can be anchored by cytoskeleton elements or lipid rafts lipids in semiolid state
  12. membranes are dynamic and are constantly forming and transforming and fusing and breaking down
  13. membranes have cabs on the outer surface that serve as recognition sites for other cells and moelcules
    glycolipids and glycoproteins
  14. cells arrange themselves in groups by cell recognition and cell adhesion
    these processes can be studied in sponge cells the cells are easily separated and will come back together again
  15. binding of cells is usually homotypic: the same molecule sticks out from both cells and forms a bond
    some binding is heterotypic the cells have different proteins
  16. help ensure directional movement of materials
    tight junctions
  17. like spot welds
  18. allow communication
    gap junctions
  19. some substances can pass through but not others in membranes
    selective permeability
  20. no outside energy required- diffusion
    passive transport
  21. energy is required for passing through
    active transport
  22. teh process of random movement toward equilibrium
  23. particles continue to move, but there is no net change in distribution
  24. new movement is directional until equilibrium is reached
    diffusion is net movement from regions of greater concentration to regions of lesser concentration
  25. diffusion trate depends on diameter of the moelcuesl or ion, temperature of the solution, electric charges, concentration gradient
    diffusion works very well over short distances
  26. membrane properties affect the diffusion of solutes
    the membrane is pereable to solutes that move easily across it and impermeable to those that cant
  27. small moelcules pass through the lipid bilayer
    simple diffusion
  28. lipid soluble moecules can diffuse across the membrane as can water
    electrically charged an polar molecules cant pass through easily
  29. the diffusion of water
  30. osmosis depends on the number of solute particles present no tthe type of particlesif 2 solutions are separated by a membrane that allows watherbut not solutes to pass throughwather will diffuse from the region of higher wather concentration (lower solute concentration) to the region of lower water concentration (higher solute concentration)
  31. equal solute concentration( and equal water concentraion)
    isotonic solution
  32. higher solute concentraion
  33. lower solute concentration
  34. water will diffuse (net movement) from a hypotonic solution across a membrane to a hypertonic solution
    animal cells may burst when placed in a hypotonic solution
  35. plant cells with rigid cell walls build up internal pressure that keeps more water from entering (TURGOR PRESSURE)
  36. polar molecules can cross the membrane through channel proteins and carrier proteins
    facilitated diffusion(passive)
  37. have a central pore lined with polar amino acids
    channel proteins
  38. important channels proteins, most are gated can be closed or open to ion passage, gate opens when protein is stimulated to change its shape. stimulus can be a molecule or electrical charge resulting from many ions
    ion channels
  39. gradients can be a concentration gradient of ions, or an electrochemical gradient resulting from a charge imbalance across the membrane
    membrane potential is a charge imbalance across a membrane
  40. water may pass through the membrane by hydrating ions that pass through a channel
    water also enters cells through special water channels called aquaporins
  41. transport polar molecules such as glucose across membranes
    carrier proteins
  42. glucose binds to the protein which causes it to change shape
  43. moves substances against a concentration gradient requires energy
    active transport
  44. active transport involves 3 kinds of proteins:
    uniports, symports, and antiports
  45. requires direct participation of atp
    primary active transport
  46. energy comes from an ion concentration gradient that is established by primary active transport
    secondary active transport
  47. primary active transport, found in all animal cells, the pump is an tegral membrane glycoprotein. it is an antiport
    sodium- potassium pump
  48. energy can be "regained" by letting ions move across a membrane with the concentration gradient- secondary active transport, aids in uptake of amino acids and sugars, uses symports and antiports
    macromolecules (proteins, polysaccharides, nucleic acids) are too large to cross the membrane, teh can be taken in or excreted by means of vesicles
  49. processes that bring molecules and cells into a eukaryotic cell ( the plasma membrane folds in or invaginates around teh material, forming a vesicle)
  50. molecules or entire cells are engulfed. some protists feed in this way. some whte blood cells engulf foreign substances. a food vacuole or a phagosome forms which fuses w a lysosome
  51. a vesicle forms to bring small dissolved substances or fluids into a cell. vesicles are much smaller than in phagocytosis. constant in endothelial cells
  52. highly specific, depends on receptor proteins integral membrane proteins - to bind to specific substances, sites are called coated pits- coated with other proteins such as clathrin
    receptor mediated endocytosis
  53. mammalian cells take in cholesterol by receptor- mediated endocytosis
    lipids are packaged by the liver into lipoproteins- secrete to boodstream
  54. liver must take up low-density lipoproteins for recycling. teh ldls bind to specific receptor proteins
  55. material in vesicles is expelled from a cell. indigestible materials are expelled. other materials leave cells such as digestive enzymes and neurotransmitters
  56. (keeping different materials separated)
    endoplasmic reticulum segregates newly-formed proteins
    • (electrically excitable membranes)
    • teh plasma membrane of neurons conducts nerve impulses
  57. membranes help transform energy:
    -inner mitochondrial membranes- energy from fuel molecules is transformed to atp
    -thylakoid membranes of chloroplasts transform light energy to chemical bonds
    membrane proteins can organize chemical reactions
  58. many cellular processes involve a series of enzyme-catalyzed reactions- all the moelcules must come together for these to occur. forms an assembly line of enzymes
    membrane proteins process info and binding of a specific ligand can initiate, stop or change cell functions
  59. the cholera toxin - one subunit binds to a cell surface receptor- the toxin molecule changes shape and allows the other subunit to enter teh cell
    -the subunit acts as an enzyme to modify a peripheral protein- this opens chloride channels in the membrane
    - cl- and na+accumulate in teh intestines, followed by osmotic loss of water
Card Set
ch5 bio
ch5 bio