Question

facilitated diffusion is different from simple diffusion because it
a moves molecules from low concentration to high concentration
b requires energy to move molecules
c only transports gases like oxygen and carbon dioxide
d requires channels or carrier proteins to move molecules across the membrane

Explanation:

Facilitated diffusion is a type of passive transport (no energy required) that moves molecules from high to low concentration (like simple diffusion). But it requires channel or carrier proteins (unlike simple diffusion where small non - polar molecules can pass through the lipid bilayer directly).

• Option a: Both simple and facilitated diffusion move from high to low concentration (in the absence of other forces).
• Option b: Neither simple nor facilitated diffusion (as it is passive) requires energy. Active transport requires energy.
• Option c: Facilitated diffusion can transport various molecules (not just sugar and carbon dioxide). For example, ions can be transported via channel - mediated facilitated diffusion.
• Option d: This is correct as facilitated diffusion (unlike simple diffusion) requires channel or carrier proteins.

Answer:

d