Question

Which of the following is most likely true of a protein that cotransports glucose and sodium ions into the intestinal cells of an animal?
A) Sodium and glucose bind to the same site on the cotransporter.
B) Transport of glucose against its concentration gradient provides energy for uptake of sodium ions against the electrochemical gradient.
C) Sodium ions can be transported whether or not glucose is present outside the cell, but glucose transport requires cotransport of sodium ions.
D) Transport of sodium ions down their electrochemical gradient facilitates the transport of glucose against its concentration gradient.
E) Following transport of sodium ions into the cell, the cotransporter can also transport potassium ions out of the cell.

Answer 1

Answer:

D) Transport of sodium ions down their electrochemical gradient facilitates the transport of glucose against its concentration gradient.

Explanation:

Active transport refers to the movement of molecules across biological membranes against a concentration gradient. Active transport can be divided into 1-primary active transport, which requires energy from the hydrolysis of adenosine triphosphate (ATP); and 2-secondary active transport, which requires an electrochemical gradient generated by pumping ions in/out of the cell. The case above described represent a type of secondary transport active because the movement of sodium (Na) ions is used as energy source to move glucose molecules against their concentration gradient.