Question

Many cells take up molecules against their concentration gradients: the molecules are more concentrated inside the cell than outside. Amino acids are frequently transported in this fashion. For the question below, think about intestinal cells growing in medium that is equivalent to blood. The concentration of amino acids is higher in the cell's cytoplasm than in the medium outside the cell.

Please indicate whether each of the following modes of transport would permit amino acid uptake into the cell. For each, please explain in one sentence why this mechanism would or would not result in amino acid uptake.

a. A sodium antiporter

b. A sodium symporter

c. An ATP-driven amino-acid pump

Answer 1

Answer: c. An ATP-driven amino-acid pump

Reason:

A sodium symporter: It often works as downhill movement of the solute molecules from a region of more concentration to the region of low concentration inorder ot allow another ion to uphill against concentration gradient. Example sodum –glucose symport. This mechanism would not allow to would permit amino acid uptake into the cell.

A sodium dependent antiport: This is mechanism in which ion molecules enable movement of ions from higher region of concentration to lower concentration region thereby enable to release some energy (exergonic reaction)..

In an antiport (NA+-K+ exchange transport) two species of ion or other solutes are pumped in opposite directions across a membrane. One of these species is allowed to flow from high to low concentration which yields the entropic energy to drive the transport. This mechanism would not allow to would permit amino acid uptake into the cell.

An ATP-driven amino-acid pump: This is the method of transport of substrate molecules into the cell by amino acid uptake via ATP hydrolysis to boost the pump for translocation of amino acid across membrane. Example of this pump ABC transporters.