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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
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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
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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
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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
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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
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Movement against a concentration gradient requires energy
a. Can be done by carrier protein
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Conformational changes
usually result of ATP hydrolysis
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ACTIVE TRANSPORT
- 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
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What drives the transport of gluten?
sodium electrochemical gradient
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Central metabolism summary
- 1. Glucose
- 2. Glycolysis
- a. Pyruvate
- 3. Citric acid cycle
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what regulates channels?
- voltage gated
- ligand gated (from inside or outside)
- mechanical gated (pressure)-toe
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Dilipid bilayer membrane can/can't get through
- CANT Get Through:
- § Large
- § Charged
- § Polar
- § Ions
- § Sugars
- § a.a
- CAN Get Through
- § Small
- § nonpolar
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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.
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What are anchors
hold cells together- A hold protein which is also held by one from other cell
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Receptors
have them in ears etc-catch=>cascade of signals=>sent to brain=>interpreting
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transporters
- let things in and out
- only allows things that fit binding site
- turnstile
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channels
- discriminate based on size and electric charge
- door w/ force field
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Define osmosis.
movement of water from area of low solute concentration(high water) to high solute concentration
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membrane potential
differnece in elextical potential
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Explain how membrane potential contributes to transport across cell membranes.
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Describe how the membrane potential is generated and maintained in animal cells.
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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
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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
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Describe how an action potential is generated and propagated in a nerve cell.
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