|By Jill Armayor, as seen on LIVESTRONG.com
Protein, made up of carbon, hydrogen, oxygen and nitrogen, is an essential component to each living cell in the human body. Protein serves as the compound necessary for cell structure repair and growth in many of the body’s tissues, such as muscle, and plays a key role in metabolism. Protein is also responsible for the formation of enzymes, antibodies, hormones, blood-clotting factors, and blood-transporting proteins. When protein is ingested, it is broken down in the stomach and small intestine by hydrochloric acid and pepsin into smaller compounds called amino acids.