Membrane protein

A protein associated with a biological membrane, either embedded in its lipid bilayer or attached to its surface. Membrane proteins enable transport, signaling, adhesion, and other interactions across or at membranes.

Lipid bilayer: A double layer of amphipathic lipids that forms the basic structure of cell membranes. Its hydrophobic interior determines which protein regions can embed in the membrane.
Ion channel: A membrane protein that forms a pore allowing selected ions to cross a membrane. Ion channels provide rapid, selective routes through the membrane.
G protein-coupled receptor: A membrane receptor that activates intracellular G proteins in response to diverse signals. This large receptor family mediates many hormone, sensory, and neurotransmitter responses.
Lipid-anchored protein: A protein covalently attached to a lipid that inserts into a biological membrane. It is membrane-associated through a lipid anchor rather than a transmembrane segment or surface interaction.
Integral membrane protein: A membrane protein embedded in the lipid bilayer, often spanning it one or more times. This is the embedded class of membrane protein.
Carrier protein: A membrane protein that binds a molecule and changes conformation to move it across a membrane. Carriers transport substrates by alternating access between membrane sides.
Sodium-potassium pump: A membrane enzyme that uses ATP to export sodium ions and import potassium ions. Its ion gradients support cell volume, electrical signaling, and secondary transport.
Soluble protein: A protein that dissolves in an aqueous cellular compartment rather than being stably associated with a membrane. Its lack of persistent membrane association marks the clearest contrast.
Peripheral membrane protein: A membrane-associated protein bound to a membrane surface or another membrane protein, without entering the bilayer’s hydrophobic core. This is the surface-associated class of membrane protein.
Membrane receptor: A membrane protein that detects an external or internal signal and initiates a cellular response. Receptors convert signals at the membrane into intracellular changes.

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