51 questions 172 174 refer to the following

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Unformatted text preview: cidate the mechanism of sucrose uptake by the marine bacterium Vibrio alginolyticus. Sucrose uptake was determined by incubating washed cells in [14 C]-sucrose for short periods of time, harvesting, rewashing the cells, and measuring the sucrose present. Uptake was measured in the presence of Na+, Na+ plus CCCP (an inhibitor of proton gradient formation), K+, and Li+. 172. Based on the data, which of the following statements best describes the uptake of sucrose by these cells? (A) Sucrose crosses the membrane by simple diffusion. (B) Sucrose is transported by a carrier-mediated system. (C) Sucrose transport is not dependent on Na+. (D) Sucrose transport occurs by only one mechanism. (E) Sucrose is not transported into the cell under most conditions. 173. The primary reason for testing the effects of CCCP is to determine whether (A) the effect of Li+ is dependent on Na+ (B) a proton gradient is required for sucrose transport (C) Na+ transport occurs alone (D) nonsaturable transport occurs (E) K+ can substitute for Na+ in sucrose transport Unauthorized copying or reuse of any part of this page is illegal. 174. Which of the following is the best explanation for the effects of Li+ and K+ on the uptake of sucrose? (A) These ions bind to sucrose and block its entry into the cell. (B) These ions decrease the net Na+ available in the cells for cotransport. (C) These ions uncouple the respiratory process that generates energy for the uptake of sucrose. (D) These ions are not transported rapidly by the Na+/sucrose cotransporter system. (E) These ions are allosteric effectors of the sucrose transporter system. GO ON TO THE NEXT PAGE. 52 Questions 175-177 The concept of species diversity has two components: evenness and richness. Evenness is based on the relative abundance of species. Richness is based on the total number of species present. Diversity indices combine a measure of richness and evenness. The Simpson index (C) is calculated from the following equation. C i ni / N 2 where ni = importance value for each species N = total importance values Below are data collected in two terrestrial plant communities that represent part of a successional chronosequence. In this case, importance values were measured as percent cover. EARLY-SUCCESSIONAL COMMUNITY Species A B C D E Percent Cover 83 5 9 2 1 LATE-SUCCESSIONAL COMMUNITY Species F G H I J Percent Cover 24 20 18 23 15 175. The Simpson index value for the late-successional community is (A) (B) (C) (D) (E) 1.00 0.410 0.205 0.0410 0.0205 177. Experimental removal of species B and C in the early-successional community resulted in a slower subsequent colonization and establishment of species F and G. This result suggests that the primary mechanism by which F and G replace B and C during succession is (A) (B) (C) (D) (E) inhibition facilitation competitive displacement allelopathy facultative mutualism 176. The data indicate that, relative to the earlysuccessional community, the late-successional community has which of the following characteri...
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