Hydrogen, nitrogen, carbon and oxygen are the main elements that make up amino acids, the basic building blocks of proteins, according to the Encyclopaedia Britannica. Other elements that can appear in proteins after post-translational modification are sulfur and selenium, Wikipedia adds.
The Royal Society of Chemistry, a British professional body, states that amino acids commonly have the chemical structure formula NH2-CHR-COOH. This formula illustrates two basic functional groups, a carboxylic acid group and an amine group, that play an instrumental role in linking individual amino acids into proteins through peptide bond formation.
There are 20 amino acids that make up the proteins found in the human anatomy, RSC states. Nine of these are essential and are obtainable only from food, while the rest are non-essential as the body can produce them itself.