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MacromoleculesBIOL222
Ch.3,4,5,and6
Ch.3-Overview:TheMoleculesofLife• Macromolecules
• largemoleculescomposedofthousandsofcovalentlyconnectedatoms
• Builtfromcarbonbackbone
• AlsocontainlargenumbersofHandO
• fourclasses:
• Carbohydrates
• Lipids
• Proteins
• Nucleicacids
MacromoleculesCH3
• Polymer
• longmoleculeconsisIngofmanysimilar
subunits
• Monomers
• Buildingblocksofpolymers
• Threeofthefourclassesofmacromoleculesare
polymers:
• Carbohydrates
• Proteins
• Nucleicacids
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• dehydra>onsynthesis(condensa>on
reac>on)
• occurswhentwomonomersbond
together
• throughthecreaIonand
subsequentlossofawater
molecule
• hydrolysis
• Processofbreakingpolymers
downtomonomers
• essenIallythereverseofthe
dehydraIonreacIon
TheSynthesisandBreakdownofPolymersCH3
Short polymer
HO 1 2 3 H HO H
Unlinked monomer
Dehydration removes a water molecule, forming a new bond
HO
H2O
H 1 2 3 4
Longer polymer
(a) Dehydration reaction in the synthesis of a polymer
HO 1 2 3 4 H
H2O Hydrolysis adds a water molecule, breaking a bond
HO H H HO 1 2 3
(b) Hydrolysis of a polymer
TheDiversityofPolymersCH3
2 3 HO H
• cellsholdhundredsofthousandsof
differentkindsofmacromolecules
• Humanscanmakeupto
150,000differentproteins
• Macromoleculardiversity
• indicaIveofbiological
diversity
• varietyofpossiblepolymers
virtuallylimitless
• fromasmallsetofmonomers
CH3
Proteins:Widerangeoffunc>ons
• Proteins
• codedinDNA
• accountformorethan50%ofthedrymassofmostcells
• ProteinfuncIons
• structuralsupport
• storage
• transport
• cellularcommunicaIons
• movement
• defenseagainstforeignsubstances
CH3
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Polypep>des• Polypep>des
• polymersbuiltfromthesamesetof20aminoacids
• Aminoacidmonomers
• ProteinconsistsofoneormorepolypepIdes
• FoldedintofuncIonal3-Dform
CH3
AminoAcidMonomers
• Aminoacids
• organicmoleculeswith
carboxylandaminogroups
• differintheirproperIes
duetodifferingsidechains
• calledRgroups
Nonpolar
Glycine (Gly or G)
Alanine (Ala or A)
Valine (Val or V)
Leucine (Leu or L)
Isoleucine (Ile or I)
Methionine (Met or M)
Phenylalanine (Phe or F)
Trypotphan (Trp or W)
Proline (Pro or P)
Polar
Serine (Ser or S)
Threonine (Thr or T)
Cysteine (Cys or C)
Tyrosine (Tyr or Y)
Asparagine (Asn or N)
Glutamine (Gln or Q)
Electrically charged
Acidic Basic
Aspartic acid (Asp or D)
Glutamic acid (Glu or E)
Lysine (Lys or K)
Arginine (Arg or R)
Histidine (His or H)
CH3
AminoAcidPolymers
• pep>debonds
• CovalentbondbetweenCand
Nlinkingaminoacids
• PolypepIdes
• rangeinlengthfromafewto
morethanathousand
monomers
• Aminoacidsequencedictatestype
ofpolypepIde
• andulImatelytypeofprotein
Peptide bond
Amino end (N-terminus)
Peptide bond
Side chains
Backbone
Carboxyl end (C-terminus)
(a)
(b)
CH3
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ProteinStructureandFunc>on• funcIonalprotein
• consistsofone(ormore)polypepIde(s)twisted,folded,andcoiledintoauniqueshape
A ribbon model of lysozyme(a) (b) A space-filling model of lysozyme
GrooveGroove
CH3
• Sequenceofaminoacids
• determinesaprotein’sthree-dimensionalstructure
• Protein’sstructuredeterminesitsfuncIon
• Fitsubstrateininspecific“lockandkey”fashion
ProteinStructureandFunc>on
Antibody protein Protein from flu virus
CH3
FourLevelsofProteinStructure• Primarystructure(1°)
• sequenceofaminoacids
• Secondarystructure(2°)
• iniIalfolding
• alpha(α)helicesorbeta(β)sheetsinthepolypepIdechain
• TerIarystructure(3°)
• interacIonsamongsidechains(Rgroups)
• combinaIonsofα-helicesandβ-sheets
• Quaternarystructure(4°)
• proteinconsistsofmul$plepolypepIdechains
CH3
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FourLevelsofProteinStructure• Primarystructure
• Sequenceofaminoacids
• DictatedbysequenceofnucleoIdesinDNA
• Codon
• setofthreenucleoIdes
• codeforaspecificaminoacid
CH3
FourLevelsofProteinStructure
Secondary Structure
β pleated sheet
amino acid subunits
α helix
• secondarystructure
• resultfromhydrogenbondsbetweenbackbonesofaminoacids
• NotRgroups
• αhelices
• coiled
• H-bondbetweeneveryfourthaminoacid
• αkeraIn-hair
• βpleatedsheet
• Accordianfolds
• AmyloidplaquesofAlzheimers
CH3
• Ter>arystructure
• CombinaIonsofhelicesandpleatedsheets
• determinedbyinteracIonsbetweenRgroups,
ratherthaninteracIonsbetweenbackbone
consItuents
• covalentbonds
• hydrogenbonds
• ionicbonds
• hydrophobicinterac>ons
• vanderWaalsinteracIons
• Strongcovalentbondscalleddisulfidebridges
mayreinforcetheprotein’sstructure
FourLevelsofProteinStructureCH3
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• Quaternarystructure
• resultswhentwoormorepolypepIdechainsformonemacromolecule
• Collagen
• fibrousproteinconsisIngofthreepolypepIdescoiledlikearope
• Hemoglobin
• globularproteinwithfourpolypepIdes:twoalphaandtwobetachains
FourLevelsofProteinStructure
Tertiary Structure Quaternary StructurePolypeptide chain
β Chains
HemeIron
α Chains
CollagenHemoglobin
CH3
Fig.5-21
Primary Structure
Secondary Structure
Tertiary Structure
β pleated sheet
Examples of amino acid subunits
+H3N Amino end
α helix
Quaternary Structure
CH3
WhatDeterminesProteinStructure?
Normal protein Denatured protein
Denaturation
Renaturation
• InaddiIontoprimarystructure
• physicalandchemicalcondiIonscanaffectstructure
• pH
• saltconcentraIon
• Temperature
• otherenvironmentalfactorscancauseaproteintounravel
• Denatura>on
• lossofaprotein’snaIvestructure
• NowbiologicallyinacIve
CH3
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ProteinFoldingintheCell• Itishardtopredictaprotein’s3Dstructurefromitsprimarystructure
• Sequencesof1.2millionproteinsknown
• Only8,5003-Dshapesknown
• Mostproteinsprobablygothroughseveralstates
• ontheirwaytoastablestructure
• Chaperonins
• proteinmoleculesthatassisttheproperfoldingofotherproteins
Hollow cylinder
Cap
Chaperonin (fully assembled)
Polypeptide
Steps of Chaperonin Action:
An unfolded poly- peptide enters the cylinder from one end.
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2 3The cap attaches, causing the cylinder to change shape in such a way that it creates a hydrophilic environment for the folding of the polypeptide.
The cap comes off, and the properly folded protein is released.
Correctly folded protein
CH3