Membrane proteins include embedded and surface-associated proteins that transport substances, receive signals, catalyse reactions, and support adhesion; Their positions explain how one membrane can perform many different cellular functions.
Coverage 2010–2023 · Updated 15 Jul 2026
Integral membrane proteins are embedded in or span the bilayer; peripheral proteins attach to a membrane surface or to another protein.
Hydrophobic amino-acid regions can sit among lipid tails, while polar regions face water or form pathways. Surface attachment does not require a protein to cross the hydrophobic core.
Classify by location: embedded/spanning means integral; surface-associated without entering the core means peripheral. Then connect location to likely function.
A channel crossing the membrane is integral; a cytoskeletal protein attached to its cytoplasmic face is peripheral.
A protein being near a membrane does not prove it spans the bilayer. Identify whether it enters the hydrophobic core.
This objective is assessed through structured response, commonly using State / Identify / Outline.
State / Identify / Outline / Describe / Explain / Label
Build the answer around this relationship: Integral proteins are embedded in the bilayer and may span it completely.
Listing non-membrane processes such as DNA replication or glycolysis as membrane protein functions.
Representative question
Describe the functions of proteins in cell membranes.
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.
