Vesicle fusion inserts glucose transporters for uptake

Steps:

• Vesicles in liver cells carry specific glucose transport proteins in their membranes.
• Upon glucose need, vesicles fuse with the plasma membrane via exocytosis.
• This embeds transport proteins into the cell surface membrane.
• Glucose enters the cell through these proteins via facilitated diffusion.

Why D is correct:

• Facilitated diffusion uses carrier proteins to transport glucose down its concentration gradient, matching the role of inserted membrane proteins.

Why the others are wrong:

• A: Exocytosis releases vesicle contents outside the cell, not enabling internal uptake.
• B: Endocytosis engulfs external materials into vesicles for cell entry, unrelated to fusion for transport insertion.
• C: Endocytosis engulfs external materials into vesicles for cell entry, unrelated to fusion for transport insertion.

Final answer: D