Final answer:
G protein-coupled receptors typically have seven transmembrane domains, playing a key role in cellular communication by interacting with a G-protein that activates other membrane proteins after ligand binding.
Step-by-step explanation:
G protein-coupled receptors (GPCRs) are a large family of membrane receptors that play crucial roles in cellular communication. They share a characteristic structure that includes seven transmembrane domains. These receptors are activated upon binding of a ligand, which then triggers an interaction with an associated G-protein on the intracellular side of the membrane.
The G-protein, in turn, activates other membrane proteins, such as ion channels or enzymes. This activation can lead to a cascade of signaling events within the cell, ultimately influencing various cellular responses. GPCRs are involved in numerous physiological processes and are significant targets for drugs in medicine.