Transporters proteins transports ions or molecules in or out of the cell. It transports ions and some hydrophilic molecules across the membrane. It regulates the intracellular composition of the cell.
Examples of transporters are Na+ pump, ligand-gated ion channels and Ca2+ ATPase.
Anchor links the membrane with intracellular molecules or extracellular molecules at either side of the plasma membrane.
Receptors are important proteins that regulate cell signalling. It helps the cell to communicate with the surrounding environment. Receptors receive chemical signal from the extracellular environment and transmit the message into the cell. The cell then decides what process to carry out via these messages.
Example of receptors is nicotinic acetylcholine receptor.
Enzymes serve as catalysts. It catalyse specific reactions, producing certain molecules that are responded by the cell.
Example of enzyme situated at the bilayer is protein kinase.
Association with Lipid Bilayer
Transmembrane proteins are proteins that extend across the lipid bilayer. Transmembrane proteins have two specific regions: hydrophobic region and hydrophilic region. The proteins are positioned in a way that the hydrophobic region is located within the bilayer where the hydrophobic tails region of the lipid molecules are. The hydrophilic region in the other hand are exposed to the intracellular or extracellular environment of the cell; interacting with molecules.
Monolayer-associated proteins are proteins that situated within the cell; or the cytosol. It interact with the inner layer of the lipid bilayer.
Lipid-linked proteins interact with a lipid molecule of the bilayer through covalent bond. It can be at the either side of the cell.
Protein-attached proteins are indirectly associated with the bilayer through other proteins which are situated within the bilayer. They are attached to the proteins through weak, noncovalent interactions. They can also be at the either side of the cell.