To build proteins, cells use a complex assembly of molecules called a ribosome. The ribosome assembles amino acids into the proper order and links them together via peptide bonds. This process, known as translation, creates a long string of amino acids called a polypeptide chain.
Proteins contain the elements carbon, hydrogen, and oxygen just as carbohydrates and lipids do, but proteins are the only macronutrient that contains nitrogen. In each amino acid the elements are arranged into a specific conformation around a carbon center.