Apentix/AP Biology/Unit 2: Cell Structure and Function/Question
AP Biologyhardmcq1 pt

Intestinal epithelial cells absorb glucose from the gut lumen against a glucose gradient using the SGLT1 protein, while the sodium-potassium pump runs continuously in the same cells. How is the pump's activity connected to glucose uptake?

A.The pump phosphorylates glucose so the sugar can bind SGLT1
B.Both proteins form one continuous channel complex spanning the membrane
C.The pump exports the glucose that SGLT1 imports, balancing concentrations
D.The pump builds a sodium gradient whose stored energy SGLT1 exploits to haul glucose inward

Explanation

Core Concept

SGLT1 couples glucose movement to sodium flowing down the gradient that the sodium-potassium pump established. Glucose itself travels uphill, powered indirectly by the electrochemical sodium gradient, which makes this secondary active transport. Blocking the pump lets intracellular sodium rise, the sodium driving force collapses, and uphill glucose absorption stops even though SGLT1 remains intact.

Correct Answer

DThe pump builds a sodium gradient whose stored energy SGLT1 exploits to haul glucose inward

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