GATE- PRACTICE QUESTION

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

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.

Questions 182-185 refer to the following model as an example of adaptive radiation and species diversification.

One of the classical examples of evolution occurs on the Galápagos Islands with Darwin's finches. The islands have always been separate from the South American mainland and vary in size and elevation. The lowlands are covered with thorn scrub, while higher elevations (found only on the larger islands) are covered with moist, dense forests. All the organisms living on these islands are descendants of species that have emigrated there, primarily from South America. In studying the finch populations, researchers have identified fourteen species, none of which are found on the mainland.

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