Is active transport when molecules move from a low concentration to a high concentration?
Active transport is the transport of molecules that requires energy, or ATP. This is most commonly used to move molecules from a lower concentration gradient to a higher concentration gradient (ie the movement of Na+ and K+ in a cell membrane), but active transport can exist anywhere, no matter the concentration gradient. Active transport is simply the only type of transport that causes molecules to deliberately go up a concentration gradient. so I’d say both are right – active transport is most common in places with concentration gradients, but they can exist anywhere.
