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Exam 2 - Cell Biology Cell Biochemistry Exam 2 Read each...

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Cell Biology / Cell Biochemistry Exam 2 Oct 17, 2006 Read each question carefully and select the single best answer. 1. The resting membrane potential of neurons is primarily determined by which of the following? a. the sodium concentration gradient b. the asymmetric distribution of phospholipids across the plasma membrane c. the concentration gradient of negatively charged metal ions d. the selective permeability of plasma membrane to calcium ions e. the selective permeability of plasma membrane to potassium ions 2. Voltage-gated sodium channels are composed of a. a single polypeptide with four homologous domains, each containing six transmembrane alpha helices b. a single polypeptide with six homologous domains, each containing four transmembrane alpha helices c. four polypeptides, each containing four transmembrane alpha helices d. four polypeptides each containing six transmembrane alpha helices 3. Which domain of the voltage gated potassium channel is forms the selectivity filter ?
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4. Which domain of the voltage gated potassium channel is forms the voltage sensor ? 5. During the action potential, which event results in re-polarization of the axonal membrane? 6. Myelinated axons conduct action potentials much faster than unmyelinated axons because .... a. myelin is an excellent insulator b. voltage gated ion channels are concentrated at the nodes c. action potential re-generation occurs only at the nodes d. all of the above e. none of the above 7. Why do action potentials propagate along the axon?
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