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 compete for the same binding site in the cotransporter.
B) Glucose entering the cell down its concentration gradient provides energy for uptake of sodium ions against the electrochemical gradient.
C) Sodium ions can move down their electrochemical gradient through the cotransporter whether or not glucose is present outside the cell.
D) The cotransporter can also transport potassium ions.
E) A substance that blocks sodium ions from binding to the cotransport protein will also block the transport of glucose.

Question

Quizplus · Accepted Answer

The correct answer is E because in a cotransport system, the transport of one molecule (in this case, glucose) is directly coupled with the transport of another molecule (sodium ions) using the same transport protein. If a substance blocks sodium ions from binding to the cotransport protein, it disrupts the function of the cotransporter, thereby also blocking the transport of glucose into the cell. This is because the transport of glucose is dependent on the sodium gradient established by the sodium ions moving down their electrochemical gradient.

Which of the Following Is Most Likely TRUE of a Protein