Proteins & Nucleic Acids

1. Proteins & Nucleic Acids • Proteins make up around 50% of the bodies dry mass and serve many functions in the body including: • Enzymes - Catalysts that selectively speed up chemical reactions • Storage • Defense against foreign substances • Structural components • Transport molecules • Movement • Cellular communications

2. Proteins • Proteins are made of one or more polypeptides made from 20 amino acids. • All amino acids contain the same backbone with amino and carboxyl side groups and differ only in their functional groups (-R). • The carbon in the middle is called the a carbon. Attached to it is the a hydrogen atom and -R. • The side chains determine the individual characteristics of an amino acid

3. Peptide Bonds • Bonds between amino acids are called peptide bonds and are formed via dehydration synthesis. • A union of many amino acids forms a polypeptide

4. Polypeptide Modification • Once linked, the polypeptide starts to fold into its conformation (3D functional structure). This folding can be spontaneous or with the aid of an additional protein (chaperonins). • Although thousands of structures are possible, the resulting structure is usually either globular (spherical) or fibrous.

5. 4 levels of protein structure • primary - sequence of amino acids • secondary - b pleat or a helix • tertiary - 3D structure aided by the formation of H-bonds, Van der Waals interactions (hydrophobic attraction), & disulfide bridges (-S-S-) • quaternary - 2 or more polypeptides wound into one macromolecule.