Proteins perform diverse and essential roles in the body. They act as enzymes (like amylase in saliva), hormones (like insulin), structural components (like keratin in hair and nails), transporters (like hemoglobin carrying oxygen), and antibodies (that defend against infections).
For example: Without hemoglobin, oxygen wouldn’t efficiently reach your brain and muscles.

Proteins such as immunoglobulins (antibodies) attach to antigens on pathogens, flagging them for destruction. Others like cytokines coordinate the immune response, directing white blood cells where to attack.
For example: After a vaccination, your body produces specific antibodies (proteins) to recognize and fight the real virus if it enters.

Protein-based hormones (like insulin, glucagon, and growth hormone) act quickly by binding to cell surface receptors and triggering intracellular changes. Unlike lipid-based hormones, they don’t need to enter the cell.
For example: After eating, insulin (a protein hormone) lowers blood glucose levels within minutes by signaling muscle and liver cells to store glucose.

Yes. A protein’s three-dimensional shape (conformation) determines how it interacts with other molecules. Globular proteins (like enzymes) have active sites that fit specific substrates, while fibrous proteins (like collagen) provide strength and flexibility.
For example: Hemoglobin’s folded shape creates pockets for oxygen to bind; a structural change can impair this function, as in sickle cell anemia.

Yes, nearly all enzymes are proteins, except for some RNA-based enzymes called ribozymes. Enzymes speed up chemical reactions by lowering activation energy and are highly specific to their substrates.
For example: Lactase breaks down lactose in milk. A deficiency in this enzyme results in lactose intolerance.