Sugar Absorption in Intestine

Steps:

• Identify glucose absorption: uses SGLT1 for secondary active transport with Na+ gradient, then GLUT2 for facilitated diffusion.
• Identify arabinose absorption: as a pentose, relies on passive facilitated diffusion via GLUT transporters, not energy-dependent.
• Match to choices: arabinose fits "active diffusion" (facilitated), glucose fits active transport.
• Eliminate mismatches based on energy requirements.

Why C is correct:

• Glucose absorption follows the sodium-glucose cotransporter law, requiring ATP-driven active transport to move against its gradient; arabinose uses carrier-mediated facilitated diffusion without energy input.

Why the others are wrong:

• A: Arabinose lacks specific active transporters, relying on passive mechanisms.
• B: Glucose needs active transport, not just diffusion.
• D: Glucose cannot rely solely on simple diffusion due to concentration gradients.

Final answer: C