BIOCHEM 2EE3 Lecture Notes - Lecture 2: Aldehyde, Lysine, Ultimate Tensile Strength
17 Sep 2016
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Document Summary
Secondary structure locally coiled into regions of helical structure. Tertiary structure helically coiled regions fold into compact structure for the entire polypeptide chain. Quaternary structure several folded polypeptide chains (subunits), arranged in a well- defined manner. Protein molecules have four levels of structural organization: primary (sequence), secondary (local folding), tertiary (overall folding), and quaternary (subunit association) Secondary structure: regular ways to fold the polypeptide chain. Rotation is possible only about the two bonds adjacent to the alpha-carbon in each amino acid residue: some kind of non-covalent bonding is necessary to stabilize a regular folding (i. e. , hydrogen bonding b/w amide protons and carbonyl oxygens) The preferred conformations of polypeptides must be those that allow a maximum amount of hydrogen bonding, yet also satisfy criteria 1-3. These two structures are the most commonly observed secondary structures in proteins. In each structure the amide group is planar, and all amide protons and carbonyl oxygens are involved in hydrogen bonding.
