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Macromolecules: proteins & nucleic acids Building Blocks of Life • Most structurally/functionally diverse macromolecule group • Involved in almost everything: • enzymes : digestive pepsin, amylase • structure : keratin (hair, feathers) collagen (connective tissue) • transport : hemoglobin (O2 transport) aquaporin (osmosis) • communication : membrane receptors (insulin glucose-uptake hormone) • defense : antibodies • movement : muscle fibers (actin & myosin) • storage : seed coat proteins PROTEINS • Central C & an H • Functional groups: • amino group • carboxyl group (acid) H O H | || —C— C—OH —N— | H R • R group (aka side chain) • Variable; different for each of 20 different amino acids • confers unique chemical properties to each amino acid Amino acid Monomer R group determines molecule charge charge affects polypeptide Ex: a point mutation in hemoglobin : folding > changes the amino acid, > changes the charge > changes the protein shape > deforming the cell R Group Peptide bonds • Covalent; via dehydration • Between NH2 (amine) of one amino acid & COOH (carboxyl) of another dehydration synthesis H2O • C–N bond formed peptide bond Polypeptide polymer Primary (1°) structure • sequence determined by gene (DNA) • change in sequence can cause a change in charge which can cause change in protein structure which can cause change in protien function sequence -> structure -> function Secondary (2°) structure • Folding and coiling along short sections of polypeptide • H bonding between adjacent R groups -helix -pleated sheet Tertiary (3°) structure Interactions between distant amino acids • hydrophobic clusters as nonpolar amino acids avoid watery cytoplasm • H bonds, ionic bonds, disulfide bridges Finally, a Protein disulfide bridges? • covalent bonds between sulfhydryl groups (SH) stabilizes 3-D structure Keratin protein in hair has many disulfide bridges – keeps its shape Quaternary (4°) structure Collagen skin & tendons Multiple polypeptides Hemoglobin Fe containing protein that carries O2 in blood R groups hydrophobic interactions disulfide bridges (H & ionic bonds) 2° RH groups bonds 1° amino acid sequence peptide bonds 3° multiple polypeptides hydrophobic interactions 4° Recap: protein structure determined by DNA Unfolding a protein • disrupt bonds & bridges temperature • pH • salinity • alters shape • destroys functionality many cannot return to functional shape Protein denaturation Nucleic Acids Information storage 2006-2007 The genetic material • stores information DNA Genes = template for proteins • DNA RNA proteins trait to • transfers information template for new cells template for next generation protein to trait • Structure • monomer = nucleotide • adenine, guanine, thymine, cytosine, uracil DNA • Types • RNA (ribonucleic acid) • single helix, ribose, uracil • DNA (deoxyribonucleic acid) • double helix, deoxyribose, thymine Examples RNA 3 parts • nitrogen base • pentose sugar (5C) ribose in RNA deoxyribose in DNA • phosphate (PO4) group I’m the A,T,C,G or U Nucleotides • purines • double ring N base • adenine (A) • guanine (G) • pyrimidines • single ring N base • cytosine (C) • thymine (T) • uracil (U) Types of nucleotides Purine = AG “Pure silver” Dehydration synthesis -> covalent bond aka phosphodiester between hydroxyl & phosphate groups polymer ‘backbone’ Nucleic acid • H-bonds between DNA nucleotide N-bases • Base-pair rule: • purine pairs with pyrimidine A :: T 2 H bonds G ::: C 3 H bonds Base Pair rule o DNA helices are complementary • via base-pair rule • can replicate entire molecule o To reproduce cell via mitosis o To make gametes via meiosis “It has not escaped our notice that the specific pairing we have postulated immediately suggests a possible copying mechanism for the genetic material.” Copying the Code James Watson & Francis Crick 1953 . o Can build RNA complement • aka transcription of genes • for eventual translation into protein Copying the Code