Principles of Proteins

Proteins Isomers Two amino acids Can Combine to form peptide bond Sequence of amino acids is important. If Sequence is reversed, a different molecule is formed "any molecule that contains a chiel Carbon atom can have both right left handed isomers. "Isomers Same molecular Formula, different Arrangement of atoms Mirror image isomers are called or Short polymers of amino acids peptides dipeptide 2 aa tetrapeptide-9 aa tripeptide 3 aa Enantiomers are a Subelast of Steamers Sterioisomers isomers that differ in the Oligopeptide 10-20 aa position of atoms in space Poly peptide 20-50 aa Cis/Trans are sterioisomers Protein 50+ aa Individual amino acids in a polypeptide or protein residues Right left handed isomers of a chiral molecule enan Hemers Residues are numbered in proteins numbered residue Identify specific Two enantiomers have the Same functional group "Underge same chemical reactions have Some physical progeries Proteins Naming Proteins "Written from left to right Start with the N-terminal (the amino acid with the free unconnected amine group) End with C-terminal (the amino acid with the free unconnected carboxyl group) "H₂N-CH-C-NH-CH-C-NH-CH-C-NH-CH-C- R₁ R₂ R₃ R₄ Peptide bond Primary Structure *planar units along a protein chain *peptide bonds are planar Yet the lone pair of electrons on N makes a partial double bond with carbonyl group Secondary Structure "regular repeating patterns of folding that occur as a result of H-bonding between atoms in the protein backbone 2 Major Forms Alpha Helix Beta Pleated Sheet Four Levels of protein Structure primary, secondary, tertiary, quaternary Straight Curled Curled twisted Proteins Tertiary Structure "Overall 3D shape Caused by attraction between atoms of Side chains Glycine Side chain interactions 3) False 5) Left side Hydrophobic interaction Salt bridge Disulfide bridge