Which one of the following statements best describes the mechanism of action of insulin on target cells?

Insulin binds to a receptor molecule on the outer surface of the plasma membrane and the hormone receptor complex activates adenylate cyclase through the Gs protein.

Insulin binds to a transmembrane receptor at the outer surface of the plasma membrane, which activates the tyrosine kinase that is the cytosolic domain of the receptor.

Insulin enters the cell and causes the release of calcium ions from intracellular stores.