Question

this video shows potassium ions moving by facilitated diffusion until they reach a state of equilibrium. select the true statements. once equilibrium is reached via facilitated diffusion, molecules stop moving completely. 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. facilitated diffusion is a form of active transport.

Explanation:

Step1: Analyze option A

Once equilibrium is reached in facilitated - diffusion, molecules do not stop moving completely. There is still a state of dynamic equilibrium where molecules move back and forth at equal rates. So option A is false.

Step2: Analyze option B

In facilitated diffusion, molecules move from an area of higher concentration to an area of lower concentration (down their concentration gradient) until equilibrium is reached. This is a key characteristic of diffusion - based processes. So option B is true.

Step3: Analyze option C

The phospholipid tails of the cell - membrane are non - polar, and charged molecules cannot easily cross them. Facilitated diffusion uses transport proteins (channels or carriers) to allow charged molecules to cross the membrane without being repelled by the non - polar tails. So option C is true.

Step4: Analyze option D

Facilitated diffusion is a form of passive transport as it does not require energy input (ATP) to move molecules across the membrane. Active transport requires energy to move molecules against their concentration gradient. So option D is false.

Answer:

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