Final answer:
There are three general categories of cell-surface receptors: ion channel-linked receptors, G-protein-linked receptors, and enzyme-linked receptors. Ion channel-linked receptors open or close ion channels in response to ligand binding, G-protein-linked receptors activate associated G-proteins to trigger signaling pathways, and enzyme-linked receptors function as both receptors and enzymes.
Step-by-step explanation:
Cell-surface receptors are involved in most of the signaling in multicellular organisms. There are three general categories of cell-surface receptors: ion channel-linked receptors, G-protein-linked receptors, and enzyme-linked receptors. Ion channel-linked receptors function by opening or closing ion channels in response to ligand binding. This allows ions to flow across the cell membrane, leading to changes in membrane potential and the generation of electrical signals.
G-protein-linked receptors bind to a ligand and activate an associated G-protein. The activated G-protein then interacts with a nearby membrane protein, such as an ion channel or an enzyme. This interaction triggers intracellular signaling pathways that produce a cellular response. Enzyme-linked receptors function as both receptors and enzymes. When a ligand binds to the receptor, it activates the enzymatic activity of the receptor, leading to the production of intracellular signaling molecules that regulate cellular processes.