Active Transport and Bulk Transport

While diffusion and osmosis are passive processes that move substances down their concentration gradients, cells also need to transport substances against their concentration gradients — from low to high concentration. This requires metabolic energy in the form of ATP. The Edexcel A-Level Biology specification (9BI0) requires you to understand active transport, co-transport, endocytosis and exocytosis.

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Active Transport

Active transport is the movement of molecules or ions across a cell membrane against their concentration gradient (from a region of lower concentration to a region of higher concentration). It requires metabolic energy in the form of ATP and involves specific carrier proteins (also called pumps) in the membrane.

How Active Transport Works