The absorption of glucose from the gut into intestinal mucosal cells is coupled to Na+,K+ ATPase. In contrast, the movement of glucose from the intestinal epithelial cells into the submucosal bloodstream occursthrough passive transpo. Given these facts, which of the following statements can be true at one time or another?
So, the core concept should mention the sodium-glucose cotransporter (SGLT) in the apical membrane and the facilitated diffusion via GLUT2 in the basolateral membrane. The correct answer would likely involve understanding that the active transport creates a concentration gradient, allowing passive movement out.
The options are A-D, but they're missing. However, the correct answer is given as one of them, which I need to infer. The user didn't provide the options, so maybe they expect a generic explanation. Wait, the user provided the correct answer as a placeholder. Maybe I should explain the scenario regardless.
In the explanation, I need to outline why the correct answer is right. The Na+/K+ ATPase creates a sodium gradient, which is used by SGLT to cotransport glucose. Once glucose is in the cell, it moves passively down its concentration gradient into the bloodstream via GLUT2. So, the correct statement would be that glucose moves passively from the cell to the blood when the intracellular glucose concentration is higher than the extracellular.
The wrong options might suggest that the movement into the cell is passive, or that the basolateral transport is active. Or maybe they confuse the direction of transport. For example, an incorrect option could claim that the movement into the cell is passive, which is wrong because it's active. Another might say the blood transport is against the gradient, which is incorrect because it's passive.
The clinical pearl here is the distinction between active and passive transport in different parts of the intestinal epithelium. Remembering SGLT for active transport and GLUT2 for passive diffusion is key for exams.
So, structuring the answer with the given sections: Core Concept, Why Correct, Why Incorrects, Clinical Pearl, and Correct Answer line. Since the options are missing, I'll focus on the correct answer's reasoning and the incorrect possibilities based on common mistakes.
**Core Concept**
Glucose absorption in the gut involves **active transport** via **Na+/glucose cotransporter (SGLT1)** on the apical membrane of intestinal epithelial cells and **passive facilitated diffusion** via **GLUT2** on the basolateral membrane. The **Na+/K+ ATPase** establishes a sodium gradient, driving secondary active transport of glucose into cells.
**Why the Correct Answer is Right**
Glucose moves **passively** from intestinal epithelial cells into the bloodstream via GLUT2 when intracellular glucose concentration exceeds that in the blood. This passive process relies on the concentration gradient established by active transport at the apical membrane. The Na+/K+ ATPase maintains the sodium gradient, enabling SGLT1 to cotransport glucose against its gradient into the cell.
**Why Each Wrong Option is Incorrect**
**Option A:** Incorrect if it claims glucose enters the cell via passive diffusion; SGLT1 requires active transport.
**Option B:**