Over the course of evolutionary time, animal body sizes have gotten larger, yet cell sizes have not. Cells have stayed proportionally the same size to remain efficient, because
A) if cells got larger, the demand for energy and raw materials would greatly decrease.
B) larger cells would become limited by the ability to move materials across the plasma membrane.
C) of limitations of the composition of the plasma membrane.
D) of the inability of the nucleus to produce sufficient DNA for larger cells.
E) the Golgi apparatus would not be able to meet the demands of cell transport of larger cells.
B
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In E. coli the heat shock response, which alters the proteins produced by the cell at different temperatures, is mediated by
A) degradation of chaperone proteins at high temperatures. B) denaturing of DNA in the promoters in the genes of heat-sensitive proteins. C) synthesis of alternative sigma factors at high temperatures to activate transcription of heat-shock genes. D) increasing the promoter affinity of already existing polymerase sigma factors at high temperatures.
Which insecticide has been outlawed in the United States but not in Latin America?
a. DDT b. pyrethrum c. inorganic phosphates d. biological insecticides e. sulfur-containing insecticides
One map unit is equal to a recombination frequency of
A) 1%. B) 5%. C) 10%. D) 50%. E) 100%.
The sulfonamide antibiotics kill bacteria by
A) interfering with cell wall synthesis B) disrupting folic acid metabolism C) reacting with bacterial cell membranes D) inhibiting bacterial motility