Question

multiple choice question
glucose is transported down its concentration gradient by protein carriers in the plasma membrane using:

• facilitated diffusion
• osmosis
• active transport
• phagocytosis

Explanation:

1. Recall the definitions of each transport mechanism:

• Facilitated diffusion: Movement of molecules down their concentration gradient with the help of protein carriers (no energy required).
• Osmosis: Movement of water across a semi - permeable membrane.
• Active transport: Movement of molecules against their concentration gradient (requires energy).
• Phagocytosis: A type of endocytosis where cells engulf large particles.

1. Glucose is a polar molecule and cannot pass through the lipid bilayer of the plasma membrane freely. It moves down its concentration gradient (from high to low concentration) with the help of protein carriers. This matches the definition of facilitated diffusion. Osmosis is for water, active transport is against the gradient, and phagocytosis is for large particles, not glucose.

Answer:

A. facilitated diffusion