Enzymes are biological catalysts that facilitate specific chemical reactions.
Other globular proteins use their shapes to ‘recognize’ foreign microbes and cancer cells. These cell-surface receptors form the core of the body’s endocrine and immune systems.
A variety of globular proteins transport small molecules and ions. Membrane transport proteins help move ions and molecules across the membrane.
Protein fibers play structural roles
Muscles contract through the sliding motion of two kinds of protein filaments: actin and myosin.
Small proteins called hormones serve as intracellular messengers in animals. Proteins also play many regulatory roles in within the cell- turning on and shutting of genes during development, for example. In addition, proteins receive information, acting as cell-surface receptors.
Calcium and iron are stored in the body by binding ions to storage proteins.