Question

select the true statements.
in facilitated diffusion, molecules move down their concentration gradient
to reach equilibrium.
once equilibrium is reached via facilitated diffusion, molecules stop
moving completely.
facilitated diffusion makes it possible for charged molecules to cross the
cell membrane without being repelled by phospholipid tails.
facilitated diffusion is a form of active transport.

Explanation:

• Facilitated diffusion is a passive transport process where molecules move down their concentration gradient (from high to low concentration) to reach equilibrium. This matches the first statement.
• In facilitated diffusion (and all forms of diffusion at equilibrium), molecules do not stop moving completely. They move in equal amounts in both directions, resulting in no net movement. So the second statement is false.
• Charged molecules (which are polar) cannot freely cross the non - polar phospholipid tails of the cell membrane. Facilitated diffusion uses transport proteins (channel or carrier proteins) to help these charged molecules cross the membrane, so the third statement is true.
• Facilitated diffusion is a form of passive transport (no energy input like ATP is required as molecules move down their concentration gradient). Active transport requires energy (usually ATP) and moves molecules against their concentration gradient. So the fourth statement is false.

Answer:

• In facilitated diffusion, molecules move down their concentration gradient to reach equilibrium.
• Facilitated diffusion makes it possible for charged molecules to cross the cell membrane without being repelled by phospholipid tails.