Regarding placental transfer of nutrients, which pairing of substance and transport mechanism is correct?

• A Glucose by simple diffusion down its concentration gradient
• B Amino acids by facilitated diffusion through GLUT transporters
• C Glucose by facilitated diffusion mediated by GLUT1 transporters ✓
• D Free fatty acids by active transport requiring ATP hydrolysis

Explanation

Glucose crosses the placenta by facilitated diffusion via GLUT1 transporters on both the microvillous and basal trophoblast membranes, moving down the maternal-to-fetal gradient without consuming energy. Amino acids require active transport against gradients using specific amino acid carriers, and fatty acids cross largely by diffusion and carrier-mediated uptake, not ATP-driven pumping. Simple diffusion applies to gases such as oxygen and carbon dioxide, not glucose.

Reference: Williams Obstetrics, 25th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.