Protein

Egg whites contain a lot of protein

Proteins are large molecules built from small units known as amino acids. These small pieces are stuck together with peptide bonds. They do different things depending on their shape. They can be found in meat or muscle. They are used for growth and repair, as well as for strengthening the bones. They help to make tissue and cells. They can be found in animals, plants, fungi, bacteria, and also in the human body. For example, muscles contain a lot of proteins. Body builders will eat foods with a lot of protein because exercise breaks down the muscles, allowing new protein to be used to rebuild them larger and stronger. Proteins form an important part in foods like milk, eggs, meat, fish, beans, and nuts. There are four things that determine what a protein will do. The first is the order that the amino acids are in. There are 20 amino acids, and they are all a bit different. The second is the little twists in the chain. The third is how the entire thing is folded up. The fourth is whether it's working with other proteins.

Animals eat proteins and break them down into amino acids in order to recombine them into other things needed, including other proteins and other amino acids. Animals have certain amino acids they are not able to create this way, and must get from their food. These are called "essential amino acids" and different animals have different amino acids they are not able to create. Meat contains all the essential amino acids humans need; most plants do not. However, eating a mixture of plants, such as both wheat and peanut butter, or rice and beans, provides all the essential amino acids needed. Soy products like tofu provide all the essential amino acids but are not the only way to get the protein you need. Amino acids are used to build new proteins that are used as enzymes, hormones, or antibodies. Protein is very important to have in your diet; it's basically what you are made of. Proteins are essential for life.

The scientist Jons Jacob Berzelius gave proteins their name, but many other scientists have studied proteins.

Other websites

• Protein from the Harvard School of Public Health