Lydia,

19. It is first necessary to recognize that oligomycin inhibited O2 consumption. From Figure 1, it is apparent that the addition of ADP had originally stimulated respiration. The most reasonable explanation for this is that ADP, as the substrate for the ATP synthase, is stimulating ATP synthesis. This would relieve the proton gradient, increase electron transport, and stimulate O2 consumption. The subsequent addition of oligomycin counteracted this effect, so the suggestion that it directly inhibits the ATP synthase is logical. Choice C is therefore the best answer: Inhibiting ATP synthesis would increase the proton gradient, decrease the electron transport, and decrease O2 consumption. Choice A should be eliminated because an uncoupler would relieve the proton gradient, which would increase electron transport and increase O2 consumption. Choice B should be eliminated because a respiratory substrate (succinate, for example) would enhance O2 consumption. Choice D is incorrect because an agonist is an activator that would stimulate ATP production and O2 consumption.

ATP synthase makes ATP. If you inhibit making ATP, you will not need as much oxygen to help with the formation. Try to keep the concepts simple. Uncoupling the proton gradient would render the ETC inefficient, and increase the demand.

31. the effect of Ca2+ binding to troponin, necessary for the generation of force, and for the reloading of Ca2+ into the SR after the stimulus, which is necessary for relaxation. This is part of the muscle contraction you should be familiar with.

57. I do not think you should focus on the specifics of these questions. Learning to answer questions from tables is a skill and with more practice, it will be less confusing. Try reading through the solutions and watching the video explanations, and when you pick up the general themes they use to answer these questions apply them to the next figure questions you answer.