3209%20Ch1-10%20Answers%20to%20Reader%20Questions - MCB...

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Unformatted text preview: MCB 3209 Answers to Reader Questions, Chapters 1­10 Ch 1, p. 4 1. Organ 2. See p. 5 slides 3. T 4. F Ch 2 p. 7 1. b 2. T 3. Each mol, no matter how big, is associated with about 300 water mols. Thus, glycogen with many glucoses reduces amt of water associated with it inside cells. 4. F, cholesterol is lipid and often associated with fat, but fat and cholesterol are different 5. T 6. a and b. Soln containing 150 mM Ca and 150 mM Cl would need another 150 mM of some anion to be electroneutral. 7. pH = ‐ log [H} = ‐ log 2 – log (10‐7) = 0.3 – (‐7) = 6.7 8. 1 g/liter = 1g/180 g/mole/liter = 5.55 x 10‐3 moles/liter 9. no, proteins are coded by DNA, not by the amino acids in the diet. 10. UCGA Ch 3, p. 14 1. F 2. tRNA 3. 25,000 4. F 5. C 6. b 7. c 8. b 9. A 10. T 11. d Ch 4, p. 21 1. F 2. T 3. a 4. D 5. T 6. F 7. T 8. T 9. T 10. F 11. T 12. F 13. These are vitamins not synthesized by the body that are used as essential cofactors or coenzymes in enzymatic reactions. 14. decrease pH any time [H] increases Ch 5, p. 22 Note changes to reader Ch 5 in bold 1. T releases energy instead of exergonic 2. T 3. T 4. T 5. F 6. T 7. F 8. T 9. F 10. F 11. T 12. T 13. d 14. d 15. None of the above 16. a 17. d 18 f 19. c 20. A Ch. 6, p. 31 1. F, there is electroneutrality in cells, though there is small separation of charge right across the membrane. 2. F, rate is determined by concentration of solute and activity of the transporter, until saturation is reached, when further concs lead to no further change of rate. 3. Na‐K pump only because this is the only one that has ATP requirement directly. The others would be affected too, but only indirectly after lack of ATP had caused loss of Na and K conc gradients and the change in concs had altered membrane voltages. Such changes would then affect activities of the other transporters. 4. A. Na and Cl and water permeant, protein not permeant. Water moves from side 1 to side 2 because protein is only impermeant molecule. Na and Cl both move by diffusion from side 2 to side 1, but there would be only a very small or no voltage (equal permeabilities). B. Na and water permeable but Cl and protein impermeable. In this case, Na would diffusion down conc gradient making side 1 more positive than side 2, but there would be no net diffusion of Na because the membrane voltage would prevent net Na diffusion. Thus, water would move from side 1 to side 2 until the concs on the two sides equilibrated and there was no more osmotic gradient.s 5. K. Hyperkalemia will depolarize cells because Ki/Ko gradient is reduced, leading to depolarizing effect on the voltage. 6. Cl secretion along with Na drags water by osmosis from blood to the intestine lumen. Eating sugar and salt provides the Na and glucose that are required to make the Na‐glucose symporter work, and these solutes will drag water by osmosis from intestine lumen to the blood to counteract the fluid secretion induced by cholera. 7. Cold temperature reduces Na/K pump activity, but K channels can still work so they leak K from the cell into the extracellular fluid and gain Na from extracellular fluid into the cell. Heating the cells reverses the events because the Na/K pump can work again to recover the losses. 8. F 9. Na movement out of the cell 10. 0.3 M glucose 11. Same answer as #7. 12. red cells shrink when osm increases to 1200 mOsm/l then recovers to control when outside osmolarity decreases back to 300 mOsm/l. 300 mOsm/l is isotonic and iso‐osmotic 1200 mOsm/l is hypertonic and hyperosmotic 13. Assuming same diffusion coefficient, net flux = difference in conc. Thus, largest differences is c. 14. b 15. e Ch. 7, p. 34 1. F – these are Schwann cells 2. F 3. F, blocker of esterase prevents breakdown of Ach and prolongation of action of Ach. 5. F, depolarization (more positive inside) will occur with inward movement of Na. 6. T 7. F 8. F, absolute refractory period results from inactivation of the Na channels. Removal of inactivation requires cell becoming negative inside again. 9. Both excitatory and inhibitory nerves release neurotransmitters that bind to specific receptors. The actions of these receptors then depolarize (excitatory) or hyperpolarize (inhibitory) the postsynaptic cell. 10. Myelin provides insulation and increases length along the axon over which the electrical voltage at one node of Ranvier spreads. This increased spread of excitability increases rate of action potential propagation. 11. Ca channels are responsible for triggering fusion of transmitter‐containing synaptic vesicles with the nerve terminal of the presynaptic cell. In the absence of Ca in the medium or extracellular space, neurotransmitter cannot be released. 12. F. This is tricky, because repolarization requires the Na/K pump to maintain the Na and K gradients across the membrane, However, repolarization of the membrane potential occurs because K diffuses out of the cell causing inside to go more negative following peak positive voltage during action potential. 13. T. Depolarization causes both activation of Na channels at modest depolarizations and then inactivations of Na channels at larger depolarizations. 14. Action potential frequency is limited by refractory period because action potentials cannot be activated during this time (usually about 1‐2 msec long). Similarly, refractory period assures one‐way transmission along axon – action potential excites adjacent membrane “in front” of the action potential but cannot excite the adjacent membrane “behind” the action potential because the refractory period is still in effect. Ch. 8 p. 43 1. F, no requirement for the primary motor cortex 2. F, both located in the brain stem 3. T, hormone release from the anterior pituitary is controlled by hormone‐releasing hormones released from the hypothalamus into the portal circulation that is used to communicate between the two structures. 4. T 5. e 6. a 7. c 8. T 9. F 10. C 11. T Ch. 9 p. 51 1. d 2. T 3. C 4. T 5. F, neurotransmitter from somatic motor nerves is acetylcholine, which causes only excitation of skeletal muscles 6. T, acetylcholine is tonically released from parasympathetic nerves, and this slows the heart. A blocker of acetylcholine action would therefore speed the heart. 7. F, Ach from parasympathetic nerves slows heart and contraction of smooth muscle in GI tract. 8. T 9. T 10. Hypertension (too high blood pressure) results in some cases from too much activation of sympathetic nervous system, resulting in too fast heart beating and too much constriction of blood vessels (arterioles). Blocking sympathetic neurotransmitter (norepinephrine) action therefore reduces these effects and lowers arterial blood pressure. Ch 10 p. 55 1. F, adaptation refers to slowing of frequency of action potentials during constant stimulation. 2. F, action potentials always same size, even though generator potentials will be larger with larger stimulus. 3. F. There are indeed more sensory nerves in the skin of the finger than in the back, and these would then have larger homunculi, but the homunculi are in the postcentral, not the precentral, gyrus. 4. F, RPE is in the back of the eye, just adjacent to the retina. 5. T 6. F Information from left side of each retina projects to the left occipital lobe while information from right side of each retina projects to the right occipital lobe. 7. T, though there is new information indicating that some mechanical receptors may respond to some specific chemicals too. 8. F, receptor potentials are graded, with different sizes yielding different frequencies of action potentials. 9. c 10. C 11. A, b and c all true 12. T 13. T 14. F (repeats 4 – sorry!) 15. More light oculomotor nerve parasympathetic nerves contract circular smooth muscle, pupil smaller ...
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This note was uploaded on 09/21/2010 for the course MCB 57703 taught by Professor Machen during the Spring '08 term at University of California, Berkeley.

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