Question

Glucose is absorbed across the intestinal epithelium into the blood (at the basolateral membrane) by which mechanism?

• A. Secondary active transport
• B. Facilitated diffusion
• C. Simple diffusion
• D. Primary active transport

Hint:

Apical entry is SGLT1 cotransport, but exit into blood via GLUT2 is carrier-mediated and passive.

Answer 1

The Correct Option is B

Step 1: Separate the journey of glucose into entry and exit across the gut cell. The lumen-to-cell step and the cell-to-blood step use different machinery.
Step 2: The exit into blood relies on the GLUT2 transporter on the basolateral side. GLUT carriers are passive uniporters - they bind glucose and flip it across the membrane following the concentration gradient, with no ATP and no ion coupling.
Step 3: That carrier-mediated, gradient-driven, energy-independent transport of a polar molecule is the textbook definition of facilitated diffusion, the same route used for amino acid exit.
Step 4: Discard the rest: a polar sugar will not slip through the bilayer by simple diffusion; primary active transport burns ATP directly and is reserved for pumps; secondary active transport is the apical SGLT1 sodium-glucose entry, not the absorption step into the bloodstream. \[\boxed{\text{Facilitated diffusion}}\]