The definition of a protein is a substance that has amino acids, compounds and carbon, hydrogen, oxygen, nitrogen, and sometimes sulfur and is found in many foods. An example of a protein is the type of nutrient found in meats.
Protein is an important component of every cell in the body. Your body uses protein to build and repair tissues. You also use protein to make enzymes, hormones, and other body chemicals. Protein is an important building block of bones, muscles, cartilage, skin, and blood. Enzymes are proteins that catalyze chemical reactions. Enzymes speed up the reactions in biological systems by lowering the activation barrier needed to start that reaction. Hormones are proteins that are chemical messengers in the body.