Pump proteins use ATP to move specific ions or molecules against concentration gradients, enabling active transport and maintained gradients; This allows cells to build and maintain gradients that diffusion cannot create.
Coverage 2012–2025 · Updated 15 Jul 2026
Pump proteins use energy, commonly from ATP hydrolysis, to move selected substances against their concentration or electrochemical gradient.
A pump changes conformation when energy is supplied, alternately exposing a binding site to each side of the membrane. This couples an unfavorable transport step to a favorable energy-releasing reaction.
Trace: bind solute → energy changes protein shape → release solute on the opposite side → reset.
An ATP-driven pump can keep sodium higher outside a cell even though diffusion would tend to move sodium inward.
A protein moving a solute is not enough to identify active transport; look for uphill movement and an energy source.
This objective is assessed through structured response, commonly using Explain / Identify / Deduce.
Explain / Identify / Deduce
Build the answer around this relationship: Pump proteins use ATP to move substances across membranes.
Calling pump proteins channels when the mark scheme rejects channels for active transport.
Representative question
Calcium is absorbed from food in the human gut by both active and passive processes. Outline active transport, including the benefits of the process.
The SL membrane model is a decision system. The bilayer forms because phospholipids are amphipathic, and the hydrophobic core creates selective permeability. Small non-polar molecules diffuse directly; water moves by osmosis and often through aquaporins; ions and polar molecules use channels or transporters; pumps use ATP for movement against gradients. Proteins and glycocalyx components add transport, recognition, and model evidence.
