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Question
Indole (the structure shown below) will cross a membrane about 1000 times faster than tryptophan. Which of the following is the most likely explanation for this phenomenon?
a. there is a specific secondary active transporter for indole while tryptophan moves by facilitated diffusion
b. indole can easily move through a lipid bilayer by simple diffusion while tryptophan movement is slowed by the presence of ionized functional groups
c. both tryptophan and indole use the same transporter protein which has a much higer affinity for indole than for tryptophan
d. since indole is not normally present in biological systems, it is not bound to proteins that would prevent transport in the manner that tryptophan is
e. none of the above
Answer
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