The shape of a protein determines its biological activity. A single protein may have varying structure and more than one function. Proteins have many different biological functions Proteins are classified according to their biological roles. Virtually all the chemical reactions of organic biomolecules in cells are catalyzed by enzymes. Many thousands of different enymes, each capable of catalyzing a different kind of chemical reaction, have been discovered in different organisms.
Digestive enzymes hydrolyze the polymers in food.
These proteins are involved in transporting other substances. For example, hemoglobin, the iron-containing protein of blood, tranports oxygen from the lungs to other parts of the body. Other proteins transport molecules across cell membranes. Structural Proteins Structural proteins are very important for support. Collagen and elastin provide a fibrous framework in animal connective tissues, such as tendons and ligaments.