3 1 Nucleic Acids are informational Macromolecules Chapter 3 Nucleic Acids Proteins and Enzymes 1 Nucleic acids DNA and RNA are polymers specialized for storage transmission and use of i DNA and the proteins encoded by DNA determine metabolic functions genetic info 2 Two types a DNA b RNA 3 Monomers are nucleotides a Consist of three components i Nitrogen containing base double ring structure ii Pentose sugar absence of one oxygen atom iii 3 phosphate groups are called nucleosides nucleoside monophosphates 1 Two chemical forms Pyrimidine six membered single ring structure or Purine fused 1 In DNA pentose sugar is deoxyribose which differs from the ribose in RNA by the 1 Molecules consisting of only pentose sugar and nitrogenous base no phosphate group 2 Nucleotides that make up nucleic acids contain just one phosphate group called 4 Linkage of one nucleotide to the next is done through condensation rxn and phosphodiester linkage joins nucleotides between sugar of one and phosphate of next a Nucleic acids grow in 5 to 3 direction 5 Nucleotides can be oligonucleotides a Olgionucelotides include RNA molecules that function as primers to being the duplication of DNA RNA molecules that regulate the expression f genes and synthetic DNA molecules used for amplifying and analyzing other longer nucleotide sequences b Polynucleotides more commonly reffered to as nucelic acids include DNA nd most RNA can be very long and are longest polymers in living world i 6 Differences a DNA i Double stranded ii adenine A cytosine C guanine G and thymine T iii sugar is deoxyribose iv structure is less flexible b c lacks hydroxyl group at 2 position b RNA same as DNA but uracil U replaces thymine T sugar is ribose i ii can form variety of structures 7 Complementary base pairing a DNA A T C G b RNA A U C G c Base pairs held by hydrogen bonds 8 RNA separate portions of molecules of bases a Usually single stranded but many can fold up into 3 D structures due to ribonucleotides in b Folded molecule by complementary base pairing and structure determined by particular order a Usually double stranded two separate polynucelotide strands of same length i Form ladder that twists double helix ii sugar phosphate groups form sides of ladder bases with their H bonds form rungs on inside 9 DNA b Uniform shape 10 Process a DNA i Purely information molecule ii Info encoded in sequence of bases carried in its strand iii Functions 1 DNA replication done by polymerization using an existing strand as base pairing template 2 DNA coped into RNA transcription polypeptide chain translation a Nucleotide sequence in RNA can be used to specify sequence of amino acids in b Overall process of transcription and translation is gene expression c Note that i DNA replication and transcription depend on the base pairing properties of ii DNA replication usually involves entire DNA molecule iii iv Sequences of DNA that encode specific proteins and transcribed into RNA are Complete set of DNA is called genome nucleic acids called genes 3 2 Proteins are polymers with important structural and metabolic roles 11 Major functions a Enzyme catalytic proteins that speed up biochemical rxns b Defensive proteins ex antibodies c Hormonal and regulatory proteins ex insulin control physiological processes d Receptor proteins recieve and respond to molecular signals from inside outside org e Storage protein store chemical building blocks amino acids for later use f Structural proteins provide physical stability and movement g Transport protein carry substances within org h Genetic regulator proteins regulate when how and what extent a gene is expressed 12 Proteins are polymers made up of monomers called amino acids a Polymeric proteins made by peptide linkages b Amino acids contain two functional groups nitrogen containing amino group and carboxylic acid group c Distinguished by R groups side chain identify amino acids d Only 20 amino acids occur extensively in proteins of all organisms e These 20 can be grouped according to properties of side chains R groups i Charged Hydrophilic group Five amino acids have electrically charged side chains attract water hydrophilic and attract oppositely charged ions of all sorts ii Polar hydrophilic group Five amino acids have polar chains and tend to form H bonds with water and other polar or charged substances also hydrophilic iii Hydrophobic group Seven amino acids have side chains that are nonpolar hydrocarbons In watery environment of cell these hydrophobic side chains may cluster together in interior of protein iv Special group Cysteine glycine and proline 1 Cystein a Has terminal SH group b Can react with other cysteine side chain to form a covalent bond called disulfide bridge S S i Determines how polypeptide chain folds 2 Glycine a Side chains consist of single hydrogen atom b small enough to fit into tight corners in interior of a protein molecule where larger side chain could not fit 3 Proline a Possess modified amino group that lacks hydrogen and instead forms covalent bond with hydrocarbon side chain resulting in a ring structure i Limits both H bonding ability and ability to rotate ii Proline often functions to stabilize bends or loops in proteins 13 Amino acids can form short polymers of 20 or fewer amino acids called oligopepties or simply peptides 14 Common longer polymers called polypeptides or proteins 15 Condensation rxn forms peptide linkage a Polymerization occur in the amino to carboxyl direction 16 Sequence of amino acids in a polypeptide chain constitutes the primary structure of a protein 17 Secondary structure consists of regular repeated spatial patterns in different regions of a polypeptide chain a H bonding between N H and C O groups within and between chains is responsible for protein s b secondary structure two basic types i alpha helix right handed coil that turns in the same direction as a standard wood screw 1 R groups extend outward from peptide backbone of helix 2 Coiling results from H bonds in N H group and C O groups ii beta pleated sheet formed from two or more polypeptide chains that are extended and aligned 1 Stabilized by H bonds in N H groups and C O groups on two chains 2 Many proteins contain both alpha and beta pletad sheets in different regions of same polypeptide chain 18 Tertiary structure Chain that is bent at specific sites and then folded back and forth a 3 D shape including a buried interior and surface exposed to the environment b Interaction between R groups