Question

Distinguish between the three classes of cell surface receptors with regards to associated cell signalling processes. (24 marks)

Answer 1

The three classes of cell surface receptors are :

1.Ion channel-linked receptors :These receptors possess ion channels that are ligand gates specifically for anions and cations whose opening and closing is controlled by neurotransmittersThey are multipass transmembrane receptors.The cell signalling process that they participate in are rapid signaling events that takes place usually in cells that are  electrically active such as the neurons.

2.G-protein-linked receptors:These receptors are integral membrane proteins with seven transmembrane helices. These receptors participate in cell signalling where activation of  a G protein takes place when an agonist binds to the receptor after which the G-protein initiates further receptor effects on intracellular signaling pathways.

3. Enzyme-linked receptors: These receptors could be are either enzymes or those that directly activate other associated enzymes. These are usuallyt single-pass transmembrane receptors in which the enzymatic component of the receptor stands out being intracellular in its location.The cell signalling that they participate include activation of other molecules by attaching or detaching specific moieties in the molecule.Most of the enzyme-linked receptors are found in association with protein kinases.