2008-2009 Most structurally & functionally diverse group : involved in almost everything (pepsin, DNA polymerase) (keratin, collagen) (hemoglobin, aquaporin) (insulin & other hormones) (antibodies) (actin & myosin) (bean seed proteins) Structure monomer = 20 different amino acids polymer = protein can be one or more polypeptide chains folded & bonded together large & complex molecules complex 3-D shape Rubisco hemoglobin H 2 O growth hormones Amino acids Structure central carbon amino group carboxyl group (acid) R group (side chain) variable group different for each amino acid confers unique chemical properties to each amino acid like 20 different letters of an alphabet can make many words (proteins) H O H N C C OH H R Oh, I get it! amino = NH 2 acid = COOH Effect of different R groups: Nonpolar amino acids nonpolar & hydrophobic Why are these nonpolar & hydrophobic? 1
Effect of different R groups: Polar amino acids polar or charged & hydrophilic Ionizing in cellular waters H+ donors Why are these polar & hydrophillic? Ionizing in cellular waters H+ acceptors Sulfur containing amino acids Form covalent cross links betweens sulfhydryls stabilizes 3-D structure H-S S-H You wondered why perms smell like rotten eggs? Building proteins covalent bond between NH 2 (amine) of one amino acid & COOH (carboxyl) of another C N bond dehydration synthesis H 2 O Building proteins Polypeptide chains have direction N-terminus = NH 2 end C-terminus = COOH end repeated sequence (N-C-C) is the polypeptide backbone can only grow in one direction peptide bond 2
Protein structure & function depends on structure 3-D structure twisted, folded, coiled into unique shape pepsin Primary (1 ) structure amino acid sequence determined by gene (DNA) slight change in amino acid sequence can affect protein s structure & its function even just one amino acid change can make all the difference! hemoglobin collagen lysozyme: enzyme in tears & mucus that kills bacteria Sickle cell anemia I m hydrophilic! Just 1 out of 146 amino acids! But I m hydrophobic! Secondary (2 ) structure folding along short sections of polypeptide interactions between adjacent amino acids weak bonds between R groups forms sections of 3-D structure Secondary (2 ) structure Tertiary (3 ) structure interactions between distant amino acids cytoplasm is water-based nonpolar amino acids cluster away from water covalent bonds between sulfurs in sulfhydryls (S H) anchors 3-D shape 3
Quaternary (4 ) structure only then does polypeptide become functional protein collagen = skin & tendons hemoglobin Protein structure (review) 1 amino acid sequence peptide bonds determined by DNA 2 R groups H bonds R groups hydrophobic interactions disulfide bridges (H & ionic bonds) 3 multiple polypeptides hydrophobic interactions 4 Protein denaturation Unfolding a protein alter 3-D shape In Biology, size doesn t matter, SHAPE matters! some proteins can return to their functional shape after denaturation, many cannot Let s build some! 2008-2009 Macromolecule Review Carbohydrates monosaccharide energy raw materials energy storage structural compounds glycosidic bond glucose, starch, cellulose, glycogen 2006-2007 4
Lipids Structure / building block glycerol, fatty acid, cholesterol, H-C chains energy storage membranes hormones fat, phospholipids, steroids ester bond (in a fat) amino acids levels of structure enzymes u defense transport u structure peptide bond signals u receptors digestive enzymes, membrane channels, insulin hormone, actin Nucleic acids nucleotide information storage & transfer DNA, RNA phosphodiester bond 5