05-08-2010, 10:43 AM
1. A series of experiments are performed to determine the mechanism by which a pharmacologic agent transverses cell membranes and accumulates within target cells. The rate of transport depends on the concentration of the drug only. When the extracellular concentration of the agent exceeds 10nM, no further increase in the rate of uptake is observed. Structurally similar compounds pass through the cell membrane, but at a lower rate. Ouabain, an inhibitor of Na+/K+ ATPase, fails to inhibit transport. Which of the following is the most likely mechanism by which this agent enters cells?
A) Antiport
B) Facilitated diffusion
C) Ion-gated coupling
D) Simple diffusion
E) Symport
A) Antiport
B) Facilitated diffusion
C) Ion-gated coupling
D) Simple diffusion
E) Symport