B a complete turn of the citric acid cycle requires

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Unformatted text preview: te dehydrogenase. (D) ADP is an allosteric activator of cytochrome oxidase, which is unable to transfer electrons to O2 without ADP. (E) The proton gradient produced by pyruvate metabolism quickly inhibits electron transport; the inhibition is released by ATP synthesis. 161. Which of the following is the most likely reason that O2 consumption stops a short time after the addition of ADP, as shown in Figure 1 ? (A) The O2 concentration has fallen to zero. (B) Most of the ADP has been phosphorylated. (C) The mitochondria have burst from excess ATP. (D) The pyruvate dehydrogenase activity has been destroyed. (E) The electron transport system has been denatured. GO ON TO THE NEXT PAGE. Unauthorized copying or reuse of any part of this page is illegal. 46 162. In Figure 2, the addition of X941 results in the nearly complete depletion of the O2 in the assay mixture. A further test showed that this depletion occurred even when inorganic phosphate was omitted from the assay. The most likely explanation for the effect of X941 is that X941 (A) allows O2 to leak out of the mitochondria (B) is a precursor to the synthesis of ADP (C) uncouples ADP phosphorylation from electron transport (D) serves as an alternative electron acceptor in the system (E) serves as an allosteric activator of pyruvate dehydrogenase 163. If X941 is an ionophore, which of the following best describes its mode of action? (A) It rearranges the mitochondrial membrane, thus allowing O2 to pick up electrons of higher energy. (B) It allows O2 to diffuse through the inner mitochondrial membrane more quickly. (C) It sequesters ions that are known to inhibit the transfer of electrons to O2. (D) It allows protons to diffuse through the inner mitochondrial membrane, thus dissipating the proton gradient. (E) It acts as an electron donor, thus providing the electron transport system with a large number of electrons to reduce O2. GO ON TO THE NEXT PAGE. Unauthorized copying or reuse of any part of this page is illegal. 47 Questions 164-167 Graphs showing the metabolic response of five different species of animals at various ambient temperature exposures are shown below. The average body mass of each of the species is 25 grams. All measurements were made using respirometers in the lab with the animals at rest and postabsorptive. GO ON TO THE NEXT PAGE. Unauthorized copying or reuse of any part of this page is illegal. 48 164. Of the species studied, which is best insulated? (A) (B) (C) (D) (E) Species Species Species Species Species A B C D E 166. Which of the following can be concluded for species C, D, and E ? (A) Metabolic costs increase with increased body mass. (B) Metabolic expenditures decrease below the lower critical temperature. (C) The lowest metabolic costs are in the thermoneutral zone. (D) The lowest metabolic costs are attained at an ambient temperature of 20°C. (E) The animals require no energy input in the thermoneutral zone. 167. Which of the following pairs of species are ectotherms? (A) (B) (C) (D) (...
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This document was uploaded on 03/16/2014 for the course BIO 1434 at UT Arlington.

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