Question

which of these provides an example of molecules moving by facilitated diffusion? a water diffuses across the phospholipid bilayer with the gradient. b na+ moves through a membrane protein against the gradient to the cytoplasm. c o2 moves from high concentration outside the blood cell to low concentration inside the blood cell. d glucose moves from high concentration in the blood to lower concentration in the cell using a membrane protein.

Explanation:

Facilitated diffusion is passive transport where molecules move down their concentration gradient via membrane proteins. Water (A) and O₂ (C) use simple diffusion through the bilayer. Na⁺ (B) moves against the gradient (active transport). Glucose (D) uses a membrane protein to move down the gradient, fitting facilitated diffusion.

Answer:

D. Glucose moves from high concentration in the blood to lower concentration in the cell using a membrane protein.