cell membrance

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cell membrance
2010-10-12 16:57:25
cell membrane lipid bilayer

details concerning cell membranes-lipid bilayer
Show Answers:

  1. Compare and contrast membrane lipids in archaea and bacteria.
    • a. Archaea: Single membrane, Plasma, Glycerol molecules may be on opposite sides of the membrane and are covalently attached,Ether link
    • b. Bacteria: Single membrane,Plasma,Ester link
    • c. Eukaryotes: Multiple membranes, Around organelles; Subtle differences in proteins causes organelle has distinct characteristics
  2. Summarize the evidence for membrane fluidity.
    • Mosaic b/c has proteins, phospholpids etc
    • Fluid b/c things can move easily around
    • Lipids in the membrane are fluid and can diffuse laterally
    • Also rotate around-spin about y-axis
    • Flip-flop-rarely- Generally needs enzyme
  3. Explain the role of cholesterol in membrane fluidity.
    • Amphipathic
    • Buffers membrane fluidity- Fits between phospholipid subunits Especially for animals w/ high body temp ie humans
    • Fill holes caused by kinked hydrocarbon tails-unsaturated
    • Prevent fatty acids from coming together and solidifying membrane=bad-Keeps F.A from being too fluid and moving apart
    • Polar head
  4. Carrier protein
    • Binds to the transported molecule
    • i. Similar to enzyme
    • b. Very discriminatory
    • c. Facilitate diffusion
    • d. Slower than channel if gate were open
  5. Channel proteins-used for ions
    • a. Don't bind with molecule
    • b. Often require certain size/charge
    • i. Ie NA ones will allows Na but not K
    • c. Often gated
    • i. If gated were to go bye bye=> rush due to such high concentration gradient
  6. Movement against a concentration gradient requires energy
    a. Can be done by carrier protein
  7. Conformational changes
    usually result of ATP hydrolysis
    • Energy comes from:
    • 1) Coupled transporter
    • a. Pos delta G w/ neg delta G
    • b. Glucose in-against 10 fold(10x more inside) w/ Na which is going DOWN gradient into cell(cell has less)
    • 2) ATP driven pump
    • 3) light driven pump
  9. What drives the transport of gluten?
    sodium electrochemical gradient
  10. Central metabolism summary
    • 1. Glucose
    • 2. Glycolysis
    • a. Pyruvate
    • 3. Citric acid cycle
  11. what regulates channels?
    • voltage gated
    • ligand gated (from inside or outside)
    • mechanical gated (pressure)-toe
  12. Dilipid bilayer membrane can/can't get through
    • CANT Get Through:
    • § Large
    • § Charged
    • § Polar
    • § Ions
    • § Sugars
    • § a.a
    • CAN Get Through
    • § Small
    • § nonpolar
  13. membrane characteristics
    • travel throuout the cell by budding off and fusing
    • mosaics of lipids and proteins-Fluid Mosaic
    • Lots of proteins etc that span membrane
    • Alpha helix w/ nonpolar A.A.
  14. What are anchors
    hold cells together- A hold protein which is also held by one from other cell
  15. Receptors
    have them in ears etc-catch=>cascade of signals=>sent to brain=>interpreting
  16. transporters
    • let things in and out
    • only allows things that fit binding site
    • turnstile
  17. channels
    • discriminate based on size and electric charge
    • door w/ force field
  18. Define osmosis.
    movement of water from area of low solute concentration(high water) to high solute concentration
  19. membrane potential
    differnece in elextical potential
  20. Explain how membrane potential contributes to transport across cell membranes.
  21. Describe how the membrane potential is generated and maintained in animal cells.
  22. Compare and contrast symport and antiport processes.
    • symport:an integral membrane protein that simultaneouly transports two substances across membrane in the same direction.
    • antiport:simutaneously transports two different molecules, in opposite directions, across the membrane
  23. Explain how patch clamping works and what it can tell us about ion channels.
    • micoroelectrode pressed against cell surface and detaches a patch of membrane current passes through membrane patch and glass microelectrode to oscilloscope which shows current passing in circuit via membrane channels
    • ion channel opens to allow positive ions to pass which is shown by increase in current-showing open channel-current at 0=closed, can watch ion channel open and close by itself without change of the voltage running across the membrane
  24. Describe how an action potential is generated and propagated in a nerve cell.