Final answer:
When a ligand binds to its receptor, conformational changes occur, leading to activation of the receptor's intracellular domain or its associated proteins through dimerization.
Step-by-step explanation:
When a ligand binds to its receptor, conformational changes occur that affect the receptor's intracellular domain. Conformational changes of the extracellular domain upon ligand binding can propagate through the membrane region of the receptor and lead to activation of the intracellular domain or its associated proteins. In some cases, binding of the ligand causes dimerization of the receptor, which means that two receptors bind to each other to form a stable complex called a dimer. The binding of the receptors in this manner enables their intracellular domains to come into close contact and activate each other.
Once a ligand binds to a receptor-enzyme, the catalytic domain interacts with intracellular components. This event activates the enzyme, which then initiates a signaling pathway inside the cell leading to a cellular response. Specifically, in the case of enzyme-linked receptors like tyrosine kinase receptors, the intracellular domains are phosphorylated upon ligand binding, which in turn leads to the activation of a signaling cascade within the cytoplasm. This signaling cascade results in a series of downstream events that ultimately cause changes in the cell's behavior or function.