👉 In biochemistry, a protein is an essential component of living organisms. Proteins are complex molecules that contain amino acids, which are organic compounds composed of carbon, hydrogen and oxygen atoms. There are two main types of proteins: polypeptide (a long chain of amino acids) and glycoprotein (a single chain of amino acids). Proteins can be found in various forms such as a protein in the cell membrane, a protein in the cytoplasm, or a protein in the nucleus