5 Elements of Protein

Proteins are known for making muscle tissue, but they also serve several other functions in the human body. The immune system uses them to create antibodies to protect you from diseases and bacteria. Your endocrine system uses them to make enzymes to trigger chemical reactions and hormones to trigger glandular functions. Proteins also provide structure for cells and bind with atoms and molecules within the body. Proteins are composed of molecules called amino acids, and each amino acid contains four elements: hydrogen, oxygen, nitrogen and carbon. Some might also contain a fifth element, sulfur.

A glass bowl filled with speckled kidney beans. (Image: AndreyGorulko/iStock/Getty Images)

Hydrogen, Oxygen, Nitrogen and Carbon

Hydrogen is the most abundant element in the universe, as well as the simplest of all the elements on the periodic table. Oxygen is the third most abundant element and makes up approximately 21 percent of the Earth's atmosphere. Nitrogen is the fifth most abundant element in the universe and the primary molecule in all proteins. Carbon is the sixth most common element in the universe and forms the basis of almost every life form on Earth. These four elements combine together to create amino acids, the building blocks of all proteins.

Amino Acid Formation

Amino acids are made of amino molecules and carboxyl acid molecules bound together by a carbohydrate bond and a side molecule known as an R-group. In the amino group, one nitrogen atom binds with three hydrogen atoms. In the carboxyl acid group, one carbon binds with one oxygen atom and one hydroxide molecule – one carbon and one oxygen. Each amino and carboxyl connects to a single carbohydrate molecule, and it is the R-group that determines the type of amino acid. For example, if the R-group is a single hydrogen atom, you'll have the amino acid glycine; if the R-group is a carbon and three hydrogen atoms, you have alanine.


Sulfur is a mineral that occurs naturally in plants such as garlic and asparagus, milk, meats and egg yolks. In fact, it is the sulfur in the yolk that makes it turn green as it cooks, and it also gives eggs and garlic their distinctive aromas. Sulfur does not occur in all amino acids, but can present in the R group of two amino acids: methionine and cysteine. In the body, sulfur converts to a chemical called methylsulfonylmethane, or MSM, and is an important component in joint health.


Proteins are composed primarily of four elements, but a fifth element, sulfur, plays a role in two amino acids. All of these elements are abundant and naturally occurring, and available in both plant and animal sources, as well as in mineral deposits in the soil and in the air you breathe.

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