What elements make up proteins?

Proteins are organic molecules composed of Carbon, Hydrogen, Oxygen and Nitrogen.
Proteins are crated by linking together amino acids into protein links called polypeptide chains. There are twenty amino acids of which 12 can be synthesized by the human body and 8 must be ingested in the foods we eat. These 8 are referred to as the essential amino acids.
Amino Acids have a basic structure of three components, an amino group made of ##-H_2N##, a carboxyl group ##-COOH## and the last group is called the R-group or variable group which is composed of Carbon, Hydrogen and Oxygen. The arrangement of the C,H and O in this group determines the name of the amino acid.