Seven Major Functions of Proteins

Enzyme

Speed up the rate of a specific chemical reaction (lactase-catalyzes the hydrolysis of lactose)

Structure

Support for tissues. Provide connections between body parts (collagen, keratin-structural protein in hair and skin)

Signaling

Chemical messengers. Send signals between cells (membrane proteins, serotonin-happiness in the brain, hormones-insulin)

Transport

Bind to specific materials and carry them around the body (hemoglobin-carries oxygen in blood, membrane proteins)

Storage

Preserve amino acids until they are needed (raw amino acids such as egg whites-albumin)

Contractile

Contract muscle fibers allowing for movement (actin, myosin)

Defense

Recognize and combine with other materials (Immunoglobins-antibodies of the immune system, cell membrane proteins)