1. Structural support: Proteins provide the framework and support for cells, tissues, and organs. For example, collagen is a fibrous protein that gives strength to skin, bones, and tendons. Keratin is another structural protein that forms hair, nails, and feathers.

2. Enzymes: Many proteins act as enzymes, which are biological catalysts that speed up chemical reactions within the body. They are essential for digestion, metabolism, and many other vital processes. For example, amylase is an enzyme that breaks down starch in the digestive system.