Considered "the building blocks" of living organisms, proteins direct many of the most basic functions in organism from the transport of oxygen, to the building of tissues to the replication of DNA. These large molecules are found in all of the cells in the human body.
The word protein comes from the Greek word proteios which means "holding first place." The very name indicates their importance to life. They help to build bones and muscles and regulate every function in the body. They also help to fight illnesses. Proteins are made up of chains of amino acids and come in various shapes. Some proteins are structural, helping to hold the body together. These are the largest proteins. Keratin, myosin, actin and collagen are examples of structural proteins. Keratin comprises skin, hair and nails in humans and fur, feathers, scales and horns in animals. Actin and myosin make up muscle tissue. Collagen comprises connective tissue. Other types of proteins have a more regulatory function, helping to orchestrate the various body processes. For example, some regulate metabolism, while others regulate such functions as muscle contractions. Proteins also activate and de-activate genes. Proteins make up more than 50 percent of a person's dry body weight.