q2 - raji_321

[ArchivalUser]

In an in vitro system designed to study glucose transport in intestinal cells, a synthetic lipid bilayer membrane containing a specific glucose transporter is suspended between two aqueous compartments, called X and Y. If the glucose concentrations in X and Y are equal, but a positive membrane potential is established in compartment X, net glucose transport occurs from compartment X into compartment Y. Which of the following glucose transporters best explains these results, and
which compartment corresponds to the inside of the cell?
A. A glucose uniport, with compartment X corresponding to the inside of the cell.
B. A glucose uniport, with compartment Y corresponding to the inside of the cell.
C. A sodium-glucose symport, with compartment X corresponding to the inside of the cell.
D. A sodium-glucose symport, with compartment Y corresponding to the inside of the cell.
E. A voltage-gated glucose channel, with compartment Y corresponding to the inside of the cell.

[ArchivalUser]

d. .. (this is a confusing q... i remember it... but the answer is still obscure... ) hi raji.

[ArchivalUser]

hi joannitam... good mornig..

D is correct..

The correct answer is D. Since the sodium-glucose symport moves net positive charge (the sodium) when it moves glucose, the net glucose transport is affected by both the electrical and chemical gradients. As with virtually all mammalian cells, normal intestinal cells have a negative membrane potential on the cytosolic face of the membrane, so compartment Y corresponds to the inside of the cell.

A glucose uniport (choices A and B) can respond only to the glucose gradient, since no net charge is moved by the transporter.

Intestinal cells have a net negative charge inside the cell, thus X corresponds to the outside of the cell, not the inside of the cell (choice C).

There are no voltage-gated glucose channels (choice E).