Question

cell membranes are selectively permeable. substances are able to move across cell membranes through the processes of diffusion and active transport. which choice best describes these processes?
passive transport
a requires energy; substances move from lower concentration to higher concentration.
b does not require energy; substances move from lower concentration to higher concentration.
c requires energy; substances move from higher concentration to lower concentration.

active transport
does not require energy; substances move from higher concentration to lower concentration.
requires energy; substances move from higher concentration to lower concentration.
does not require energy; substances move from lower concentration to higher concentration.

Explanation:

Passive transport is a process where substances move across the cell membrane without the need for energy input. This movement occurs from an area of higher concentration to an area of lower concentration, following the concentration gradient. In contrast, active transport requires energy (usually in the form of ATP) as it moves substances against their concentration gradient, from an area of lower concentration to an area of higher concentration.

Answer:

B. Substances move from lower concentration to higher concentration; requires energy.