Biochemistry, Primary Protein Structure

Proteins are polypeptide structures consisting of one or more long chains of amino acid residues. They carry out a wide variety of organism functions, including DNA replication, transporting molecules, catalyzing metabolic reactions, and providing structural support to cells. A protein can be identified based on each level of its structure. Every protein at least contains a primary, secondary, and tertiary structure. Only some proteins have a quaternary structure as well. The primary structure is comprised of a linear chain of amino acids.The secondary structure contains regions of amino acid chains that are stabilized by hydrogen bonds from the polypeptide backbone. These hydrogen bonds create alpha-helix and beta-pleated sheets of the secondary structure. The three-dimensional shape of a protein, its tertiary structure, is determined by the interactions of side chains from the polypeptide backbone. The quaternary structure also influences the three-dimensional shape of the protein and is formed through the side-chain interactions between two or more polypeptides. Each protein at least contains a primary, secondary, and tertiary structure. Only some proteins have a quaternary structure as well.