Biochemistry Cheat Sheet PDF

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Summary

BIOCHEMISTRY !generally!deals!with!the!physical!and!chemical!properties!of!compounds!that!that!make!up!the!smallest!unit!of!life!and!how!these!compounds!undergo!processes!and! relate!it!with!how!it!affects!the!daily!function!of! human!beings.!!!I.! AMINO/ACIDS//8! These! are! organic! carboxylic! ac...

Description

BIOCHEMISTRY! generally! deals! with! the! physical! and! chemical! properties! of! compounds! that! that! make! up! the! smallest!unit!of!life!and!how!these!compounds! undergo!processes! and!relate!it!with!how!it!affects!the!daily!function!of! human!beings.!!

! I.! 8! 8! 8! 8! 8!

AMINO/ACIDS/ / These! are! organic! carboxylic! acids! that! has! at! least! one! amino! group! replacing! a! hydrogen! atom! of! the! hydrocarbon!chain.!! All!of!the!20!amino!acids,!with!the!exception!of!Glycine,!are!levorotatory!since!glycine!doesn’t!have!an!asymmetric! carbon,!hence!it!cannot!exhibit!stereoisomerism.!! Sulfur!containing! o! Cysteine!and!Methionine! Glycine! o! Acts!as!an!inhibitory!neurotransmitter;!antagonized!by!strychnine! In!a!protein!chain,!the!α!8!carboxyl!group!of!each!amino!acid!is!joined!by!peptide!bonds!covalently!to!the!α!8!amino! group!of!the!next!amino!acid! ! NAME/ 3/LETTER/ 1/LETTER/ CLASSIFICATION/ STRUCTURE/ SYMBOL/ SYMBOL/ Alanine! Ala! A! Aliphatic! ! (Hydrophobic!Side! Chain)!

Isoleucine!

Ile!

I!

Aliphatic! (Hydrophobic!Side! Chain)!

Leucine!

Leu!

L!

Aliphatic! ! (Hydrophobic!Side! Chain)!

Methionine!

Met!

M!

Aliphatic! (Hydrophobic!Side! Chain)!

Valine!

Val!

V!

Aliphatic! (Hydrophobic!Side! Chain)!

Phenylalanine!

Phe!

F!

Aromatic! (Hydrophobic!Side! Chain)!

Tryptophan!

Trp!

W!

Aromatic! (Hydrophobic!Side! Chain)!

!

!

!

!

!

Tyrosine!

Tyr!

Y!

Aromatic! (Hydrophobic!Side! Chain)!

!

Asparagine!

Asn!

N!

Polar!Neutral!Side! Chain!

Cysteine!

Cys!

C!

Polar!Neutral!Side! Chain!

Glutamine!

Gln!

Q!

Polar!Neutral!Side! Chain!

Serine!

Ser!

S!

Polar!Neutral!Side! Chain!

Threonine!

Thr!

T!

Polar!Neutral!Side! Chain!

Aspartic!Acid!

Asp!

D!

Acidic!

Glutamic!Acid!

Glu!

E!

Acidic!

Arginine!

Arg!

R!

Basic!

Histidine!

His!

H!

Basic!

Lysine!

Lys!

K!

Basic!

Glycine!

Gly!

G!

Unique!

Proline!

Pro!

P!

Unique!

!

!

!

!

!

!

!

!

!

!

! !

! !

! ! ! ! ! !

II.!

PROTEINS/

! 8! 8!

The!major!cell!components!that!play!a!big!role!in!all!biological!processes! These! are! organic! compounds! with! high! –! molecular! weights! that! contain! nitrogen! with! complex! structural! organization! 8! Contain!amino!acids!linked!by!covalent!peptide!bonds! 8! Amphoteric!in!nature! ! A.! Protein/Structures/ 8! Structurally! organized! into! four! levels! (with! each! level! having! its! proper! specificity):! PRIMARY,! SECONDARY,! TERTIARY,!and!QUATERNARY!! ! 1.! Primary/Structure/ / o! The!simplest!level!of!structural!organization!composed!of!the!amino!acid!resides!linked!through!peptide! bonds! o! The!sequence!is!written!from!left!to!right!(N8!Terminal!to!C!–!Terminal!amino!acid)! o! In!an!electric!field:!Positively!charged!proteins!8>!Cathode!(8)!;!Negatively!charged!proteins!8>!Anode!(+)!;! Proteins!at!the!isoelectric!pH!8>!no!migration!since!net!charge!is!0! ! 2.! Secondary/Structure/ !

8! 8!

o! α!8!Helix! !! A!helical!configuration!of!the!polypeptide!chain!formed!by!the!Hydrogen!bonding!between!the! peptide!groups!of!every!first!and!fourth!AA!residues.! ! o! β!8!Sheets! !! Pleated!sheet!structure!resembling!an!accordion! !! Can!be!in!a!form!of!a!parallel!or!an!antiparallel!chain! !! Examples!are!Keratin,!Collagen,!and!Fibroin! !! Creutzfeldt!–!Jakob!Disease! •! Caused!by!the!transmission!of!Prions!(a!proteinaceous!infectious!agent!that!causes! neurodegenerative!diseases)!that!results!to!the!misfolding!of!the!normal!prion!protein! found!abundantly!in!the!brain! o! Prions!causes!Mad!Cow!Disease! •! Replacement!of!the!normal!α!8!helical!arrangement!of!the!normal!prion!protein!with!β!8! pleated!sheet! •! Dementia!and!Involuntary!Jerking!Movements!(Startle!Myoclonus)! ! 3.! Tertiary/Structure/ / o! Refers!to!the!spatial!arrangement!of!the!polypeptide!chain! o! Can!either!be!Fibrous!or!Globular! o! Different!bonds!contribute!to!the!stabilization!of!the!structure! !! Covalent!bond:!Disulfide!Bond! !! Polar!bonds:!Hydrogen!bonding,!Ionic!bonding! !! Non8Polar/!van8der8Waals! o! Chaperones! !! Proteins!that!assist!in!the!folding!and!unfolding!of!the!polypeptide!to!correctly!form!the!tertiary! structure! !! Example:!Heat!Shock!Proteins! ! 4.! Quaternary/Structure/ ! o! Spatial!arrangement!of!proteins!made!up!of!several!polypeptide!chains,!with!each!peptide!chain!having! a!tertiary!structure! o! Referred!to!as!Oligomers! o! Example:!Hemoglobin! ! ! Denaturation/(Denativation)!of!proteins!happen!when!certain!agents!such!as!heat!and!urea!destroy!the!higher! structural!levels!of!protein!without!destroying!the!peptide!bonds! Renaturation/(Renativation),!on!the!other!hand,!is!the!recovery!of!the!protein!from!its!denatured!state!!

! ! ! ! ! !

! B.! Medically/Important/Proteins/ / 1.! Hemoglobin/ o! Globular!Transport!Protein!for!Oxygen/ o! Contains!Heme!which!is!a!complex!of!porphyrin!ring!and!a!Ferrous/ o! Sickle!Cell!Anemia/ !! Caused!by!a!mutation!in!hemoglobin!where!the!Glutamate!at!position!six!in!the!beta!–!chain!of! hemoglobin!is!replaced!by!Valine/ o! Has!higher!affinity!to!CO!than!CO2/ / 2.! Collagen/ o! Found!mainly!in!the!bones!and!cartilage! o! Mainly!contains!Glycine,!Proline,!Hydroxyproline! o! Types:! !! I!–!Found!in!skin!and!bones! •! Osteogenesis/Imperfecta!is!a!disorder!in!the!synthesis!of!Type!I!collagen!characterized! by!a!distinctive!blue!sclera!and!predisposed!multiple!childhood!fracture/ !! II!–!Found!in!the!Cartilage! !! III!–!Found!in!the!arterial!walls! !! IV!–!found!in!the!basal!lamina ! !! V!–!Found!in!the!hair!and!placenta! o! Ehlers!–!Danlos!Syndrome! !! A!group!of!connective!tissue!disorders!that!are!generally!characterized!by!hyperextensible!skin,! joint!hypermobility,!and!defects!in!large!blood!vessels! ! 3.! Insulin! o! A!polypeptide!hormone!produced!by!the!beta!–!cells!of!the!pancreas! o! Synthesis!of!Preproinsulin!in!the!rough!ER!8>!Proinsulin!is!cleaved!in!the!secretory!granules!8>!C!–!petide! is!released!8>!the!remaining!molecule!forms!Insulin! ! C.! Qualitative/Tests/for/Proteins/&/Amino/Acids! ! 1.! Biuret!Test! o! Identifies!the!presence!of!proteins! o! Uses!1%!NaOH!and!a!solution!of!Copper(II)!sulfate! o! Positive!Result:!Violet!Color! ! 2.! Ninhydrin!Test! o! Uses!Ninhydrin!to!detect!the!presence!of!amines! o! Positive!Result:!Purple!(Ruhemann’s!Purple)!=!Amino!Acids!with!a!free!amino!group,!Yellow!=!Imino! Acids!(Proline!&!Hydroxyproline)! ! 3.! Xanthoproteic!Test! o! For!Tyrosine,!Tyrptophan! o! Uses!conc.!HNO3!and!40%!NaOH! o! Positive!Result:!Yellow!Color! ! 4.! Millon’s!test! o! Specific!for!Tyrosine! o! Uses!Mercury!dissolved!in!conc.!HNO3! o! Positive!Result:!Yellow!Coloration! ! 5.! Hopkins’s!–!Cole!Test! o! Specific!for!Tyrosine!(indole!group)! o! Uses!Glyoxylic!Acid!in!Glacial!Acetic!Acid!and!Sulfuric!Acid! o! Positive!Result:!Purple!Color!on!the!surface! ! 6.! Nitroprusside!Test! o! Specific!for!Cysteine! o! Uses!nitroprusside!in!alkaline!solution! o! Positive!Result:!Red!Coloration! !

7.! Sakaguchi!Test! o! Specific!for!Arginine!(guanido!group)! o! Uses!NaOH,!α!8!naphthol,!and!Bromine!solution! ! ! !

!

III.! 8!

ENZYMES/

/ These!are!biological!catalysts!of!protein!nature!which!catalyzes!energetically!feasible!reaction!without!altering!the! reaction!route.!Like!other!nonbiological!catalysts,!enzymes!are!not!consumed!during!a!reaction!and!decreases!the! Ea!of!a!reaction.!

! 8!

Enzymes!are!highly!specific!for!their!substrates!and!products!with!most!enzymes!recognizing!only!1!compound! as!substrate.!!

8!

The!velocity!of!a!reaction!is!directly!proportional!with!temperature!at!an!optimal!pH! o! However,!as!the!temperature!goes!higher!than!37!degrees!(Celsius),!enzymes!start!to!degrade! o! !Changes!in!pH!can!cause!changes!in!reaction!and!may!cause!enzymes!to!denature! !! Pepsin:!optimal!pH!is!2! ! Many!enzymes!require!cofactors!or!coenzymes!to!catalyze!reactions.!These!coenzymes!are!commonly!derived! from!vitamins!and!metal!ions.!

!

8! !

A.! Nomenclature/ / 1.! Oxidoreductases! o! Catalyzes!REDOX!reactions! o! Also!called!as!dehydrogenases!or!reductases! 2.! Transferases! o! Catalyzes!reactions!involving!the!transfer!of!different!groups!from!the!substrate!to!another! o! Amino!Transferases,!Methyl!Transferases! 3.! Hydrolases! o! Catalyzes!the!substrate!bond!cleavage!by!adding!water! o! Amylase,!Saccharase! 4.! Lyases! o! Catalyze!bond!–!cleaving!reactions!without!oxidation!or!addition!of!water! o! Pyruvate!decarboxylase! 5.! Isomerases! o! Catalyzes!structural!rearrangements! o! Triose!Isomerase! 6.! Ligases! o! Also!called!as!synthetases! o! Catalyzes!the!addition!of!2!moleculesusing!ATP!as!energy!source! o! DNA!–!Ligase! ! B.! Inhibition/ 8! Inhibitors!are!agents!capable!of!exerting!a!specific!deterrent!action!on!the!activity!of!en!enzyme/ / 1.! Competitive! o! An!inhibitor!that!is!structurally!related!to!the!substrate!binds!to!the!active!center!preventing!the! formation!of!the!enzyme!–!substrate!complex! 2.! Noncompetitive! o! An!inhibitor!binds!to!the!enzyme!or!enzyme!–!substrate!complex!which!leaves!the!active!center!free!and! may!induce!conformational!change!which!hinders!the!formation!of!the!enzyme!–!substrate!complex.!! 3.! Irreversible/ o! An!inactivator!binds!covalently!to!the!enzyme!and!inactivates!it.!/ / C.! Isoenzymes/ / 8! Also!known!as!isozymes! 8! These!are!enzymes!that!may!differ!in!amino!acid!sequences!and!physical!properties!but!catalyze!the!same! reaction! !

! IV.!

DNA/&/RNA/

/ A.! DNA/Structure/

8! 8! 8!

Contains!nucleotides!that!is!made!up!of!a!nitrogenous!base,!deoxyribose,!and!phosphate! The!nitrogenous!bases!are!classified!into!Purines!and!Pyrimidines! The!primary!structure!of!DNA!and!RNA!is!a!linear!polynucleotide!chain!made!up!of!mononucleotides!which!are! linked!by!a!3’,5’!–!phosphodiester!bond!(3’!–!C!of!one!sugar!to!the!5’!–!C!of!the!next!sugar)!

! /

/ / / / / / / / / / / / B.! DNA/Double/Helix/ 8! Proposed!by!Watson!and!Crick!in!1953/ 8! The!secondary!structure!of!DNA!is!formed!by!the!pairing!two!polynucleotide!chains!that!are!antiparallel./ o! One!chain!runs!5’!–!3’!and!the!other!3’!–!5’/ o! The!base!sequences!of!the!two!strands!are!complementary/ !! Adenine!and!Thymine!via!2!hydrogen!bonds!(major!groove)/ !! Guanine!and!Cytosine!via!3!hydrogen!bonds!(minor!groove)/ 8! One!full!turn!of!the!DNA!helix!contains!10!nucleotides.! 8! Has!3!different!conformations:! o! B!Form:!Right!Handed! o! Z!Form:!Left!Handed! o! A!Form:!Dehydrated!and!compact;!Right!Handed! ! C.! Denaturation/ 8! Separation!of!the!DNA!strands!due!to!heat!or!alkali!exposure!without!breaking!the!phosphodiester!bond/ / D.! Renaturation/ 8! Upon!heating,!DNA!strands!separate!and!the!base!pairs!reform!once!the!temperature!is!slowly!decreased!! ! E.! Hybridization/ 8! A!single!strand!of!DNA!or!RNA!pairs!with!a!complementary!base!sequence!on!another!strand!of!DNA!or!RNA! ! F.! Histones/ 8! These!are!small,!basic!proteins!rich!in!Arg!and!Lys;!not!present!in!prokaryotes! 8! Eukaryotic!chromatins!consist!of!a!DNA!complexed!with!histones! ! G.! RNA/vs./DNA! 8! RNA!contains!ribose!as!sugar!instead!of!deoxyribose! 8! Uracil!replaces!Thymine!!

! Single!stranded!with!extensive!base!pairing! RNAs!can!sometimes!act!as!catalysts!and!enzymes!(ribonucleases,!Peptidyl!transferase)! ! H.! Types/of/RNA/ 8! 8!

/ 1.! Messenger!(mRNA)! o! Contains!a!cap!consisting!of!a!methylated!guanine!triphosphate!attached!to!the!hydroxyl!group!on!the! ribose!at!the!5’!end! o! The!poly(A)!tail!contains!up!to!200!Adenine!nucleotides! ! 2.! Ribosomal!(rRNA)! o! Aids!in!the!formation!of!ribosomes! o! Prokaryotic:!70S!(Large!subunit!=!50S!;!Small!subunit!=!30S)! o! Eukaryotic:!80S!(Large!subunit!=!60S!;!Small!subunit!=!40S)! !

! ! !

3.! Transfer!(tRNA)! o! Has!a!characteristic!cloverleaf!structure!

!

V.!

DNA/REPLICATION! !

8!

Known!as!the!transfer!of!genetic!information!within!a!single!class!of!nucleic!acids,!i.e.!from!DNA!to!DNA!or,!as!in! certain!viruses,!from!RNA!to!RNA.!! 8! DNA!Replication!is:! o! Bidirectional! !! Replication!begins!at!a!specific!origin!and!simultaneously!moves!out!in!both!directions! !! Prokaryotes!have!one!site!of!origin!while!eukaryotes!can!have!multiple!sites!of!origin! ! o! Semiconservative! !! The!resulting!daughter!DNA!contains!one!intact!parental!strand!and!one!newly!synthesized! complementary!strand! ! A.! Steps/in/Replication/ / 1.! Initiation! a.! The!parental!DNA!is!separated!and!uncoiled!by!helicases!where!the!uncoiled!DNA!strand!serves!as!the! template! b.! As!the!strands!separate,!an!active!site!for!synthesis!known!as!replication!fork!is!formed!where!each! separated!strand!is!stabilized!by!a!single!–!stranded!binding!protein! c.! As!the!strands!separate,!supercoiling!happens!which!is!removed!by!DNA!Topoisomerase! !! Etoposide!inhibits!topoisomerase! d.! The!Primase!aids!in!the!production!of!the!RNA!primer!in!a!5’!–!3’!direction!! ! 2.! Elongation!&!Termination! a.! From!the!initiation!site,!DNA!Polymerase!III!adds!deoxyribonucleotides!at!the!3’!OH!end!of!the! primer! !! DNA!polymerase!can!only!copy!in!a!3’!–!5’!direction!and!produce!the!daughter!strand!in!a!5’!–!3’! direction! !! DNA!polymerase!always!requires!primers!and!cannot!initiate!the!formation!of!new!strands! b.! DNA!Polymerase!III!forms!continuous!strands!in!a!3’!–!5’!direction!forming!the!leading!strand! c.! In!the!5’!–!3’!strand,!a!discontinuous!formation!of!DNA!happens!forming!smaller!fragments!known! as!Okazaki!fragments.!These!fragments!are!joined!together!by!DNA!ligase! d.! Once!complete,!RNA!primer!is!removed!by!the!exonuclease!acivity!of!DNA!Pol!I!! e.! Gaps!are!filled!with!the!complementary!bases! f.! Replication!is!terminated,!forming!2!daughter!DNA!molecules.! ! VI.! 8! 8! 8! 8! 8!

RNA/TRANSCRIPTION/ / The!process!of!making!an!RNA!from!a!DNA!template!is!known!as!transcription.! It!is!the!major!control!point!in!gene!expression!and!protein!production.!! Catalyzed!by!DNA!–!dependent!RNA!polymerase! No!primer!is!needed! Uses!one!strand!of!DNA!as!template!

A.! 8! 8! 8!

RNA/Polymerase/ Can!initiate!synthesis!of!new!chains!without!a!primer! Copies!the!DNA!template!in!a!3’!–!5’!direction!and!the!resulting!RNA!elongates!in!a!5’!–!3’!!direction! Precursors:!Ribonucleoside!Triphosphates!(ATP,!UTP,!GTP,!and!CTP)!

/

! B.! Steps/in/Prokaryotic/Transcription! / 1.! Initiation!and!Elongation! ! o! Rifampin!inhibits!the!beta!subunit!of!Bacterial!dependent!RNA!Polymerase! o! Actinomycin!D!binds!to!DNA!and!inhibits!the!elongation!of!RNA!Transcription!by!RNA!Polymerase! ! a.! RNA!polymerase!is!directed!by!the!sigma!factor!to!bind!to!the!promoter!! o! Promoters!contain!a!sequence!TATAAT!known!as!the!Pribnow!box!or!TATA!BOX! o! In!eukaryotes,!Hogness!box!(TATA!Box)!has!a!sequence!of!TATATAA! b.! An!RNA!Polymerase!–!closed!promoter!complex!is!formed! c.! The!DNA!unwinds!at!promoter!and!forms!the!open!promoter!complex! d.! RNA!polymerase!initiates!the!mRNA!synthesis!with!a!purine!ribonucleoside!triphosphate!

! ! ! !

e.! RNA!polymerase!holoenzyme!catalyzes!the!elongation!of!mRNA!by!about!4!more!units! f.! Upon!reaching!about!10!nucleotides,!the!sigma!–!subunit!dissociates!and!will!bind!to!another!RNA!Polymerase!

! 2.! Termination! ! a.! Intrinsic!(Rho!–!independent!Transcription!Termination)! o! Controlled!by!specific!sequences!called!termination!sites!wherein!the!sequences!form!a!hairpin!loop! structure!that!allows!the!RNA!Polymerase!to!detach!from!the!DNA!template!strand! ! b.! Rho!–!dependent!Transcription!Termination! o! Involves!the!Rho!–!Protein! o! The!rho!–!protein!binds!to!the!RNA!and!chases!the!polymerase!until!it!reaches!the!termination!site!to! facilitate!the!dissociation!of!the!RNA!Polymerase!from!the!DNA!Template!Strand.! / C.! Eukaryotic/Transcription! / 1.! RNA!Polymerases!(Promoters)! a.! RNA!Pol!I!! !! Found!in!the!nucleoulus!and!synthesizes!the!precursors!of!ribosomal!RNA! b.! RNA!Pol!II! !! Found!in!the!nucleoplasm!and!synthesizes!mRNA!precursors! !! α!8!Amanitin!(a!toxin!from!the!mushroom!Amanita'phalloides)!binds!and!inhibits!RNA!Pol!II! which!halts!mRNA!synthesis!resulting!to!severe!GIT!symptoms,!liver!toxicity,!and!death.!! c.! RNA!Pol!III! !! Found!in!the!nucleoplasm!and!synthesizes!the!tRNA!precursors! ! 2.! Steps/in/Eukaryotic/Transcription/ / a.! mRNA!Synthesis/ 1.! RNA!Polymerase!II!produces!a!heterogenous!nuclear!RNA!(hRnNA)!containing!exons!and!introns/ !! Exons!are!sequences!appearing!in!the!mature!mRNA/ !! Introns!are!the!non8coding!region!and!are!removed!during!splicing/ 2.! The!primary!transcript!(hnRNA)!is!capped!at!the!5’!end/ 3.! A!poly(A)!tail!with!a!nucleotide!length!range!of!20!–!200!!is!added!at!the!3’!end!of!the!transcript/ 4.! The!introns!are!removed!and!the!exons!are!connected!to!form!the!mature!mRNA!through!splicing/ / 3.! Reverse/Transcription/ o! The!process!of!transcribing!the!single!stranded!RNA!into!a!double!–!stranded!DNA!! o! Enzyme:!Reverse!Transcriptase!(RNA!–!dependent!DNA!polymerase)!! o! Retroviruses!contain!RNA!as!genetic!material! /

VII.! RNA/TRANSLATION/AND/PROTEIN/SYNTHESIS/ / A.! Genetic/Code/ 8! A!collection!of!codons!that!specify!all!the!amino!acids!found!in!proteins! 8! Characteristics:! o! It!is!degenerate!(Redundant;!Many!amino!acods!have!numerous!codons)! o! It!is!non!–!overlapping! !! Begins!with!the!start!codon!AUG!(Methionine)!near!the!5’!end!of!the!mRNA!which!determines! the!reading!frame! !! Ends!with!a!stop!codon!(UGA,!UAA,!UAG)!near!the!3’!end! o! The!code!is!commaless!(no!markers!to!differentiate!one!codon!from!one!another)! o! The!code!is!nearly!universal! 8! Codons! o! A!sequence!of!3!bases!in!mRNA!that!specifies!a!particular!Amino!Acid! ! B.! Mutations! 8! Mutations!in!DNA!are!carried!over!into!the!mRNA!that!causes!changes!in!the!encoded!protein! ! 1.! Point!Mutations! o! A!base!in!the!DNA!is!replaced!by!another!which!alters!the!codon!in!the!mRNA! ! a.! Silent! o! The!codon!containing!the!changed!base!codes!for!the!same!amino!acid! b.! Missense!

o! The!codon!containing!the!changed!base!codes!for!a!different!amino!acid! c.! Nonsense! o! The!codon!containing!the!changed!base!codes!for!a!stop!codon! ! ! !

! 2.! Insertions! o! Occur!when!a!base!or!a!number!of!bases!are!added!to!the!DNA! ! 3.! Deletions! o! Occur!when!a!base!or!a!number!of!bases!are!added!to!the!DNA! ! 4.! Frameshift! o! Occurs!when!the!number!of!bases!added!or!deleted!is!not!a!multiple!of!3!which!shifts!the!reading!frame! to!a!completely!different!set!of!codons! ! C.! Steps/in/Eukaryotic/Translation/ / 1.! Initiation! ! a.! The!40S!ribosomal!subunit!binds!close!to!the!5’!cap!until!it!recognizes!the!start!codon!(AUG).! !! The!ribosome!recognizes!the!AUG!in!the!correct!context!known!as!the!Kozak!Sequence! (ACCAUGG)! !! In!prokaryotes,!Streptomycin!binds!to!the!30S!subunit!which!hinders!initiation! b.! A!special!initiator!tRNA!recognizes!the!start!codon!car...