Final answer:
The hormone cell, such as glucagon or epinephrine, binds to cell-surface receptors of liver and muscle cells, triggering a signaling pathway involving G-proteins and the production of secondary messengers like cAMP.
Step-by-step explanation:
The cell that binds to receptors of liver and muscle cells is a hormone cell, such as the pancreatic hormone glucagon or the hormone epinephrine. When hormones like these bind to cell-surface receptors, which are found on the outer surface of target cells, a complex signaling pathway is initiated. This pathway involves the use of G-proteins and the generation of secondary messengers such as cyclic AMP (cAMP), produced by the enzyme adenylyl cyclase during the activation process. This cAMP then activates protein kinase A (PKA) and leads to a diverse set of cellular responses, including altering metabolic pathways and synthesizing proteins.
In contrast, internal receptors located in the cytoplasm bind to small hydrophobic ligands, such as steroid hormones, which can cross the plasma membrane. These receptor-ligand complexes then move to the nucleus to interact directly with cellular DNA and mediate gene expression. Cells use different types of these receptors to respond to the same hormones differently, depending on the receptors' signaling components and the cell's specific genes that produce these receptors.