HomeworkQuestions(WeekII) - Label the selectivity filter,...

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Study Questions – Week 2 1. What are the approximate transfer rates of ion channels? How does this range of rates compare with those of transporters? 2. Describe three mechanisms cells use to produce diversity of ion channel structure and function. 3. What experimental approaches have been used to obtain the amino acid sequences of ion channels, for example the nicotinic cholinergic receptor and the shaker K channel? 4. Draw a diagram of the muscle nicotinic acetylcholine receptor (nAChR) showing its subunit composition. To which subunit does acetylcholine (ACh) bind? How many ACh binding sites are present on the nAChR? 5. How does the subunit composition of the neuronal nAChR differ from that of the muscle nAChR? 6. What are hydropathy indices and how do they help us draw inferences about channel subunit structure? 7. How does the structure of the voltage-activated K channel (K v ) differ from those of the Na v and Ca v channels? 8. Draw a diagram of the bacterial K channel crystallized by Mackinnon.
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Unformatted text preview: Label the selectivity filter, central cavity, and the arrangement of transmembrane segments. 9. How does this channel flux K ions at a rapid rate (what is the rate?) while maintaining such a high level of ion selectivity? 10. What is meant by rectification? Draw a current-voltage plot showing the characteristic behavior of an inward rectifying channel. 11. What is meant by primary vs. secondary transport? How does this terminology relate to pumps and transporters? 12. Describe the forces driving movement of ions through ion channels, ion pumps (ATPases), and ion transporters (exchangers, antiporters, symporters). 13. What property of the Na/K pump makes it electrogenic? 14. How does the Na/Ca exchanger extrude Ca from the cytoplasm? What could cause this exchanger to run in reverse? Can all exchangers run in reverse? 15. Write the equation for the reversal potential (V r ) of Na-Ca exchanger. 16. Why is the lumen of synaptic vesicles so acidic?...
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This note was uploaded on 01/31/2011 for the course CBNS 120 taught by Professor Adams during the Winter '10 term at UC Riverside.

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