1. Enzymes: These proteins act as catalysts, speeding up biochemical reactions in the body. They are highly specific, each enzyme working on a particular reaction. For example, digestive enzymes break down food, while other enzymes are crucial for building molecules.

2. Structural Support: Proteins provide structural support to cells, tissues, and organs. For example, collagen is a protein that forms strong fibers in connective tissues like skin, tendons, and bones. Keratin is another structural protein, found in hair, nails, and skin.

3. Antibodies: These proteins are part of the immune system, defending the body against foreign invaders like bacteria and viruses. Antibodies recognize and bind to specific pathogens, marking them for destruction by other immune cells.