Understanding Proteins: Structure, Function, and Role in Biology, Slides of Biology

Download Understanding Proteins: Structure, Function, and Role in Biology and more Slides Biology in PDF only on Docsity! Proteins Docsity.com Proteins Multipurpose molecules (2 ene) Docsity.com 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) —N— H H C—OH || O R | C— | H Oh, I get it! amino = NH2 acid = COOH Docsity.com Effect of different R groups: Nonpolar amino acids Why are these nonpolar & hydrophobic?  nonpolar & hydrophobic Docsity.com Effect of different R groups: Polar amino acids  polar or charged & hydrophilic Why are these polar & hydrophillic? Docsity.com Sulfur containing amino acids • Form disulfide bridges – covalent cross links betweens sulfhydryls – stabilizes 3-D structure You wondered why perms smell like rotten eggs? H-S – S-H Docsity.com Building proteins • Peptide bonds – covalent bond between NH2 (amine) of one amino acid & COOH (carboxyl) of another – C–N bond peptide bond dehydration synthesis H2O Docsity.com Building proteins • Polypeptide chains have direction – N-terminus = NH2 end – C-terminus = COOH end – repeated sequence (N-C-C) is the polypeptide backbone • can only grow in one direction Docsity.com Sickle cell anemia I’m hydrophilic! But I’m hydrophobic! Just 1 out of 146 amino acids! Docsity.com Secondary (2°) structure • “Local folding” – folding along short sections of polypeptide – interactions between adjacent amino acids • H bonds – weak bonds between R groups – forms sections of 3-D structure • α-helix • β-pleated sheet Docsity.com Secondary (2°) structure “am A Electrostatic VF asteledon Hydrogen bonding Protein structure (review) amino acid sequence peptide bonds 1° determined by DNA R groups H bonds R groups hydrophobic interactions disulfide bridges (H & ionic bonds) 3° multiple polypeptides hydrophobic interactions 4° 2° Docsity.com Protein denaturation • Unfolding a protein – conditions that disrupt H bonds, ionic bonds, disulfide bridges • temperature • pH • salinity – alter 2° & 3° structure • alter 3-D shape – destroys functionality • some proteins can return to their functional shape after denaturation, many cannot In Biology, size doesn’t matter, SHAPE matters! Docsity.com Let’s build some Proteins! 2008-2009 EAT X Docsity.com