**Question:** Glucose symport occurs with

A. Sodium ions (Na+)
B. Chloride ions (Cl-)
C. Potassium ions (K+)
D. Hydrogen ions (H+)

**Correct Answer:** D. Hydrogen ions (H+)

**Core Concept:** Glucose symport is a process in which glucose molecules are transported into cells in conjunction with the movement of another ion, typically hydrogen ions (H+). In this case, glucose moves into the cell along with the movement of hydrogen ions out of the cell.

**Why the Correct Answer is Right:** Glucose symport is primarily associated with sodium-glucose co-transport (SGLT) proteins, which are located in the brush border membrane of the small intestine and renal proximal tubule cells. The primary function of these proteins is to facilitate the transport of glucose into the cell along with the movement of sodium ions (Na+) against their concentration gradient. In this process, hydrogen ions (H+) are also transported out of the cell. Thus, option D is correct.

**Why Each Wrong Option is Incorrect:**

A. Sodium ions (Na+): Although sodium ions are involved in glucose transport via sodium-glucose co-transporters, the correct answer is hydrogen ions (H+) because glucose movement is directly linked to the movement of hydrogen ions.

B. Chloride ions (Cl-): Chloride ions are not directly associated with glucose symport; the correct answer is hydrogen ions (H+) instead.

C. Potassium ions (K+): Potassium ions are not involved in glucose symport, making this option incorrect.

**Clinical Pearl:** Understanding glucose symport is essential for understanding glucose absorption in the small intestine and renal proximal tubule cells. This process plays a critical role in maintaining glucose homeostasis and regulating electrolyte concentrations in the body.