Describe the structures of proteins

Primary structure - a sequence of amino acids in a polypeptide chain. They are joined together by peptide bonds. The sequence of amino acids determines the rest of the proteins structures. Secondary structure - Hydrogen bonds form between the amino acids causing the straight chain to coil. Depending on the amino acids in the primary sequence will determine the secondary structure, Hydrogen bonds can form to either create alpha helix or beta pleated sheets. Hydrogen bonds occur between the electronegative elements in and hydrogens joined to other electronegative elements which made but the amino acids. Tertiary structure - The secondary structure begins to coil and fold more as more bonds form. These bonds include more hydrogen bonds, ionic bonds and disulfide bridges. Disulfide bridges are formed between the sulfurs of two cysteine amino acids which are near each other. This makes a 3D, globular protein. Quarternary structures - Some larger proteins are made of several polypeptide chains. These are held together by bonds. Some protein's quarternary structure contains a non-protein prosthetic group ie iron in haemoglobin.