LifeWhat is necessary for life?Most life familiar to us: EukaryotesFirst appeared ~ 1.5 - 2 ¥ 109 years agoRequirements: DNA, proteins, lipids, carbohydrates,complex structure, ~ 104 - 105 genesFREE LIVINGOr ParasitesProkaryotes (Bacteria and Archaea)Requirements: DNA, protein, lipids, carbohydrates,simpler structure, few thousand genesFREE LIVINGOr ParasitesFirst appeared ~ 3 - 4 ¥109 years agoVirusesDNARNAProteinsViroids, Prions?PlasmidsRNAFew hundred basesFew thousand basesProteinParasitesThe tobacco-mosaic virus is made up of a strand ofnucleic acid encased in a rod of one kind of protein.LifeCompositionProperties and DefinitionsFossil record & ClassificationMinimum Requirements for LifeProteins and Nucleic Acids(Lipids and Carbohydrates)Polymers and MonomersMacromoleculesProteins made of amino acids (20)Construction and catalysis (enzymes)Nucleic acids made of nucleotidesbase sugar phosphateH, C, N, O (S)H, C, N, O (P)Carbohydrates made of sugarsEnergy (food) + structure [starch] [cellulose]Lipids (hydrocarbons + carboxyl)Membranes + Energy [water-resistant]H, C, OH, C, (O)SugarGlucosehydrocarboncarboxylLipidsFatty acid is composed of a hydrocarbonchain with a carboxyl group at one endPolysaccharidesProteinsMonomers are amino acids 20 kindsHHHHHN C COOa bcAminogroupcarboxylgroupGlycineAmino group(hook)carboxyl group(eye)SchematicSection of Protein… …HHNHCOOeye end hook endBeforeAfterPeptideBondChemicalLevelHHNHCOOeye endhook endamino acidsproteinNucleic Acids (DNA, RNA)Made of sugars, phosphates, basesRibose Sugar5C, 5O, 10 HSugarSchematicDeoxy Ribosephosphatesugars & phosphates linkedphosphodiester bondsSegment of side of ladder structureNucleic Acids (cont.)Bases: Carry Genetic CodePurinesAGAdenineGuaninePyrimidinesCU TCytosineUracil / ThymineRNA / DNABases in Nucleic acids: Purines and PyrimidinesPurinesPyrimidinesNucleic Acids (cont.)Segment of RNASegment of DNANote that T replaces U in DNADeoxyribosePhosphateDeoxyribonucleic Acid (DNA)Segment of DNA……Information Storage• Nucleic acids store information• The information specifies proteins• The information can be replicated• This allows inheritanceBase pairing rulesA - T G - C- Ufi Replication of order (reproduction)Nucleic Acid - Protein Genetic CodeCodon3 base sequence Amino AcidGeneSequence of codons Protein 1 gene 1 proteine.g. tobacco mosaic virus 4 genesbacteria ~ 103 geneshuman cell ~ 30,000 - 40,000 genesFor mRNA Genetic CodeUCAGGlycineGlycineGlycineGlycineAspartic AcidAspartic AcidGlutamic AcidGlutamic AcidAlanineAlanineAlanineAlanineValineValineValineValineGUCAGUCAGUCAGThird RNABASESerineSerineArginineArginineAsparagineAsparagineLysineLysineThreonineThreonineThreonineThreonineIsoleucineIsoleucineIsoleucineStart/MethionineAArginineArginineArginineArginineHistidineHistidineGlutamineGlutamineProlineProlineProlineProlineLeucineLeucineLeucineLeucineCCysteineCysteineStopTryptophanTyrosineTyrosineStopStopSerineSerineSerineSerinePhenylalaninePhenylalanineLeucineLeucineUGACUFirstRNABaseAmino AcidsNuclear MembraneCell MembraneTransport to cytoplasm forProtein synthesis (translation)Chain ofamino acidsanticodoncodonsDNAmRNA TranscriptionMature mRNA mRNAStructure of a tRNATranslationVariations in the Code1. “Wobble” BasesThe third base in a codon can sometimes vary.tRNA mRNA U A or G G C or UComparison to genetic code fi no changein amino acids2. Some organisms use slightly different codes,with one or more changes in codon translation.First seen in mitochondrial DNA.Now known in some nuclear DNAThe code has evolved since the last commonancestor (But not much).Summary1. Atoms needed: H,C, O, N, small amountsof P (phosphorus), S (sulfur)2. Two basic molecules needed for life:proteins, nucleic acids3. Both are polymers - made of simplermonomers. The monomers function aswords or letters of alphabet. Information isthe key.Summary (cont.)4. Proteins and nucleic acids closely linked atfundamental level. Communicate throughgenetic code. All organisms have almostthe same genetic code. It must haveoriginated very early in evolution of life.5. In present day organisms, protein synthesismust be directed by nucleic acids, butnucleic acid reading or replication requiresenzymes (proteins). Chicken-Egg
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