Why are active transport proteins called pumps?

Explanation:

ATP is the most common source of energy for active transport. As molecules are moving against their concentration gradients, active transport cannot occur without assistance. ... These proteins are often called “pumps” because they use energy to pump the molecules across the membrane.

Active Transport protein can also be referred as integral or intrinsic protein so these protein are directly incorporated within the lipid bilayer. These proteins are believed to provide a channel through which water soluble substances could pass in and out of the cell and organelles