Cellssmallestlivingunit 8/27/08DNAasthegeneticmaterial1 permeablemembrane selfreplicate2identicalcells(nearperfectcopies) slightchangesoccur Prokaryotes bacteria,bluegreenalgae cellwall(polysaccharides) plasmamembrane(lipid/protein) nonucleus Eukaryotes yeast,tetrahymena,insects,plants,mice,men oftenmulticellular nocellwall(exceptplants=cellulosewall) plasmamembrane nucleusandotherorganelles Thebasicmolecularprocessesinbacteriaandhumancellsareverysimilar whatdoesthissuggest? molecularprocessesbywhichorganismssurvivearehighlyconserved advantagesanddisadvantagestostudyingbacteria,etc. advantage:replicatesfast,easytostore,cheap,singlecells,nomoral problems, diseases dependsonproblemyouwanttoaddress Mostbiologicalreactionsutilizeenzymes enzyme=proteinsthatpossessspecificcatalyticactivitieswhichenablethemtobring 2 differentmoietiestogetherinacloseenvironment,therebypermittingachemical occur nucleicacidscanhaveenzymaticfunctions
b c
smallergenomes disadvantages:nucleartransportstudiesneedseukaryote,cantstudymost
reactionto
a
DNA
RNA
Protein
lotsofenzymesareneededforeachstep Smallcellularmoleculesusuallysubstratesandproductsofmetabolicpathways
- 4 general categories: 1. Sugars used to make larger molecules like polychains or DNA CH2OH
5
OOH
1
4
DRibose (sugarforRNA) OH
3
OH
2
2.FattyAcidsusedtomakelipids CH3CH2CH2CH2CH2COOH 3.AminoAcids(20differentRgroups) usedtomakeprotein H2NCHCOOH R ex:ifR=H,itisglycine 4.Nucleotidesusedtobuildnucleicacidsandothercomponentsincell(ex:
ATP,GTP)
3
ex:palmiticacidCH3(CH2)14COOH
backboneissameforallaminoacids
N
4
5 N 1
6
5
7
2
N 6 1 Pyrimidine (ex:uracil)
2
4
8 N9
N
H
Purine (ex:adenine) H2NCHCOOH
R
Proteinsconsistsofchainsofaminoacids H2NCHCOOH R H2NCHCOOH
R
Peptide directionality(by
R
R
carbon O
R
O O Ctermunless
NendNH 2CHCNHCHCNHCHCOHCend convention,Nterm great H 2O H 2O rotational otherwisestated) freedom BasicAminoAcids knowbackbone +H 3NCH knowbasicaminoacidsandtheirstructure lysine,arginine,histidine allhavenetpositivecharge knowcodesofbasicaminoacids lysine=lys,K arginine=Arg,R Histidine=His,H hydrophilic,oftenfoundontheoutersurfaceoftheprotein Acidicaminoacidsnetnegativecharge aspartate(Asp,D) glutamate (Glu,E) hydrophilicalso Polaraminoacidshydrophilic aspargine (Asn,N) glutamine(Gln,Q) Serine(Ser,S) Threonine (Thr,T) Nonpolaraminoacids hydrophobic;oftenfoundontheinterioroftheprotein Proteinmodifications posttranslationaladditionstoRgroups 1.phosphorylationadditionofphosphategroup(PO 4)totheRgroupofSerine, threonine, or tyrosine changes chargeofprotein peptidebonds(veryrigid)
2 .Acetylationadditionofacetylgroup(CH3COH)totheRgroupoflysine 3.Methylationadditionofamethylgroup(CH3)totheRgroupoflysine playroleingeneregulation asparagines ProteinDiversity orderofaminoacids numberofaminoacids +/(charge)modifications helixvs.helixbackboneonly 2strands antiparallelsheet(2polypeptidechains)
4.glycosylationadditionofacarbohydratesidechain(sugar)totheRgroupof