Note: There are two types of proteins: globular and structural. There are more types of globular proteins than there are types of structural proteins. Globular proteins function as enzymes (e.g. pepsin), hormones (e.g. insulin), membrane pumps and channels (e.g. Na+ / K+ pump and voltage gated sodium channels), membrane receptors (e.g. nicotinic receptors on a post-synaptic neuron), intercellular and intracellular transport and storage (e.g. hemoglobin and myoglobin), osmotic regulators (e.g. albumin), in the immune response (e.g. antibodies), and more.