Question:easy
Glucose is absorbed in the intestine by which transport mechanism?
Glucose is absorbed in the intestine by which transport mechanism?
Show Hint
Think of the carrier that moves a large polar sugar down its gradient without spending ATP.
Updated On: Jun 24, 2026
- Secondary active transport
- Facilitated diffusion
- Simple diffusion
- Primary active transport
Show Solution
The Correct Option is B
Solution and Explanation
Step 1: Recall that membrane carriers fall into a few classes. A primary active transporter splits $ATP$ at the protein itself, a secondary active transporter rides on an ion gradient set up by a pump, and a facilitated diffusion carrier simply opens a path for a solute to slide down its own gradient with no energy spent.
Step 2: Place glucose in this scheme. Crossing the brush border it is dragged in against gradient by $SGLT1$, coupled to the inward $Na^+$ gradient maintained by the $Na^+/K^+$ ATPase, which is secondary active transport.
Step 3: Crossing the basolateral side, glucose is now concentrated inside and leaves through the $GLUT2$ transporter purely along its gradient. A bulky, water-loving molecule moving through a protein channel without energy is textbook facilitated diffusion, which is the option the examiner wants.
Step 4: Eliminate the rest. Glucose is far too polar for simple diffusion through the bilayer, and no glucose carrier directly burns ATP, ruling out primary active transport.
\[\boxed{\text{Facilitated diffusion}}\]
Step 2: Place glucose in this scheme. Crossing the brush border it is dragged in against gradient by $SGLT1$, coupled to the inward $Na^+$ gradient maintained by the $Na^+/K^+$ ATPase, which is secondary active transport.
Step 3: Crossing the basolateral side, glucose is now concentrated inside and leaves through the $GLUT2$ transporter purely along its gradient. A bulky, water-loving molecule moving through a protein channel without energy is textbook facilitated diffusion, which is the option the examiner wants.
Step 4: Eliminate the rest. Glucose is far too polar for simple diffusion through the bilayer, and no glucose carrier directly burns ATP, ruling out primary active transport.
\[\boxed{\text{Facilitated diffusion}}\]
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