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CB Lecture 5-6 B
Lipids, Membranes, and Membrane Transport
| Question | Answer |
|---|---|
| How do integral membrane proteins get into the membrane? | cross membrane once; cross membrane multiple times; greasy feet; bound to another membrane protein |
| How to proteins span the membrane bilayer? Solution 1 | multiple amphipathic helices can associate to form a channel through the lipid bilayer. |
| How to proteins span the membrane bilayer? Solution 2 | beta-Barrels proteins function as transporters |
| FRAP | Fluorescence Recovery After Photobleaching. It's how proteins diffuse in the plane of the membrane. |
| How are the proteins restricted of their mobility? | anchored to the cytoskeleton or the extracellular maxtrix; bound to another cell; enclosed by a diffusion barrier |
| What can pass through the lipid bilayer? | small hydrophobic molecules (O2, CO2, N2, Benzene); small unchared polar molecules (H2O, Glycerol, Ethanol) |
| What CAN'T pass through the lipid bilayer? | Larger polar molecules (amino acids, nucleotides, sugars); ions (H+, Na+, K+, Ca, OH-) |
| What are the two major classes of membrane transport proteins? | Channels and carriers |
| Channels | form a pore in the membrane, allowing molecules to pass through membrane and down gradient |
| Carriers | transfer molecules across membrane. Does not form an open channel. |
| What kind of "things" require carrier to transport them through the membrane? | lysosome, nucleotides, sugars, amino acids, Na+ and K+, ATP and ADP, Pyruvate |
| What does passive transport mean? | there is no energy involved, "things" goes from high to low concentration; down Gradient |
| What is active transport? | Up gradient; requires energy, from low to high concentration. |
| Where does the energy for active transport come from? | ATP, light, electrons |
| What is Na+ K+ ATPase do? | uses energy of ATP hydrolysis to pump Na+ out and K+ in |
| Explain how Na+ K+ ATPase works. Step 1-3 | 1) 3 Na+ bind to cyotplasmic domain 2) PO4^ -2 transferred from ATP to protein, ADP released. 3) Na+ transferred across membrane. |
| Explain how Na+ K+ ATPase works. Step 4-6 | 4) 2 K+ bind to external domain. 5) PO4^ -2 cleaved from protein. 6) K+ transferred across membrane |
| What is the net of the Na+ and K+ of Na+ K+ ATPase? | 3 Na+ out and 2 K+ in per ATP |
| Electrogenic pump | creates a voltage across membrane. |
| Plants use (blank) for symport in place of (blank) | H+, Na+ |
| How is the osmotic equilibrium of animal cells maintained? | by the Na+ K+ pump |
| What if the Na+ and K+ pump is inactivitated with oubain if if ATP is depleted?? | Ion gradient collapses, and water is drawn into cells by osmosis. Cell swells and bursts |
| How does plant cells oppose osmotic swelling forces? | by cell walls |
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