Why is active transport called an uphill transport?

Active transport

1. Active transport is a type of transport that occurs across the cell membrane and involves the expenditure of the cell’s energy.
2. This energy is obtained from ATP (adenosine triphosphate).
3. It occurs against a concentration gradient i.e., from low concentration to high concentration and so it is also called an uphill transport.
4. It is unidirectional and highly selective.

Final answer

Active transport is called an uphill transport because it occurs against the concentration gradient.