Functions of proteins in the cell membrane


Channel: allows specific substance to move through water-filled pore. Most plasma membranes include specific channels for several common ions.

Transporter: transports specific substances across membrane by changing shape. For example: amino acids, needed to synthesize new proteins, enter cells via transporters.

Receptor: recognizes specific ligand and alters cell’s function in some way. For example, antidiuretic hormone binds to receptors in the kidneys and changes the water permeability of certain plasma membranes.

Enzyme: catalyzes reaction inside or outside cell (depending on which direction the active site faces). For example, lactase protruding from epithelial cells lining your small intestine splits the disaccharide lactose in the milk your drink.

Cell Identity Marker: distinguisher your cells from anyone else’s (unless you are an identical twin). An important class of such markers are the major histocampatability (MHC) proteins.

Linker: anchors filaments inside and outside to the plasma membrane, providing structural stability and shape for the cell. May also participate in movement of the cell or link two cells together.  

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