試題詳解

26. You are studying the entry of a molecule into red blood cells. You determine the rate of movement across the membrane under a variety of conditions and carry out the following results: 1. The molecules can move across the membrane in either direction. 2. The molecules always move down their concentration gradient. 3. No energy source is required for the molecules to move across the membrane. 4. As the difference in concentration across the membrane increases, the rate of transport reaches a maximum. The mechanism used to get this molecule across the membrane is most likely:
(A) simple diffusion.
(B) facilitated diffusion.
(C) active transport.
(D) pinocytosis.
(E) There is not enough information to determine a mechanism.