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MCB-2 Block-3 Gems-2
Ox Phos
18
Microbiology
Graduate
06/19/2011

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Term
NADH deh(NADH-q reductase) Flavoproteins
Definition

Prostetic groups of NADH deh: FMN(flavin mononucleotied) FAD(flavin adenine dinucleotide)

 

Flavoproteins have Fe-S clusters. (single e- carrier) 2 electrons and 2 protons pass onto prosthetic gorup

Term
Cytochromes
Definition

e- carriers containing Fe-porphyrin as prosthetic group Similar to heme but Fe undergoes valance change.

 

Heme in c/c1(IV) attached to S of proteins

 

Heme in a/a3 attached non covalently to membrane lipids

Term
Ubiquinone(coenzyme Q)
Definition
Highly diffusible in lipid membrane.

Carries 2 hydrogens. Functions as single e- carrier by forming free-radical intermediate.

Some e-can escape and form O2-(superoxide)
Term
Which complexes have Fe-Clusters?
Pump H+?

Ox phos
Definition
I,II,III have Fe-s clusters to accept then pass e-

I,II,IV pump protons into intermembrane space. I/III 4H+. IV = 2H+

NADH = 10H+. FADH= 6h+
Term
NADH-Q reductase complex I
(NADH dehydrogenase)
Definition
Contains FMN,FAD and several Fe-S centers

e- pass form NADH -> FMN -> Fe-s -> CoQ

NADH -> NAD+
Term
Cytochrome C reductase(Complex III)
Definition
Contain cytochrome b, Fe-S, Cytochrome C

e- pass from Co-Q(ubiquinone -> cyt B -> Fe-S -> Cyt C

Cyt C moves along intermembrane space to complex IV
Term
Cytochrome Oxidase Complex(complex IV)
Definition
Two heme near 2 Cu atoms clamp O2 during reduction to H2O Extremely high O2 affinity and activity Cu required*
Term
Succinate-FAD dehydrogenase(complex II)
Definition
Reduce leakage of e- away from CoQ

Entry point for FADH

Succinate dehydrogenase and glycerophosphate shuttle bypass complex I and utilize FADH2 instead

FADH = 2 atp. NADH = 3 atp.
Term
ATP synthase(Complex V)
Definition
Makes 3 ATP per turn.

Rate of Ox phos limited by availiablity of ADP

No allosteric control of Ox Phos
Term
Nucleoside diphosphate kinase
Definition

ATP donates Pi to create triphosphates

GTP-Signaling

UTP-Activates sugars

CTP-activates sialic acids(NANA)

Term

Inhibitors of Ox Phos

Rotenone

Barbiturates

Antimycin A

cyanide

CO

Aresenate

Definition

Rotenone: inhibits e- flow from Fe-s complexes to ubiquinone(I)

barbiturates: Inhibit e- flow through NADH-Q complex(I)

 

Antimycin A: Blocks e- flow through cytochrome C reductase(III)

Cyanide: Inhibits by binding to Fe+++ in cytochrome a/a3

 

Co binds to Fe++(IV)

Arsenate: competes with Pi on Pi transporter and pi binding site on atp synthase

Term
Uncouplers of Ox Phos
Definition
Pentachlorophenol and 2,4 ditrophenal

Blocks ATP synthase

Elevated NADH oxidation and O2 consumption -> hyperthermia

Allow some H+ across inner membrane (protonophores)

Billirubin also uncouples: brain damage in infants.
Term
Functions of pentose phosphate pathway
Definition
Create
NADPH: reductive biosynthesis
Ribose-5-phosphate: nucleotides
Sugar-phosphates

Very active in RBC. NADPH needed to protect against ROS. (NADH however still reduces Fe+++ in methemoglobin)
Term
G-6-P dehydrogenase
Definition
1st step in Oxidative phase of pentose pathway.

G-6-P -> 6-phosphogluconolactone + NADPH
Oxidation

NADPH is an potent allosteric Inhibitor
(major regulatory step)
Term
6-phospho-gluconate dehydrogenase
Definition
3rd step in Oxidative phase of pentose phosphate pathway.

6-phospho-gluconate -> ribulose-5-phosphate + NADPH + CO2

Oxidative decarboxylation

NADPH is an inhibitor
Term
Transketoloases
(non oxidative phase of Pentose P pathway)
Definition
Transfer 2-carbon keto groups(TPP)

Require thiamin pyrophosphate(TPP) Covalently bound to enzyme via schiff base(C double bond to NH2 of lysine)

X-5-P + Ribse-5-P <-> G-3-P + Sedohehptulose-7phosphate

X-5-P + E-4-P <-> G-3-P + F-6-P

Xylulose donates the carbons
Term
Transaldolase
Definition
Requires no coenzymes

Sedoheptulose + G-3-P <-> Erythrose-4-P and F-6-P

Sedoheptulose donates 3-c aldo fragment
Term
Wernicke-korsakoff syndrome
Definition
Transketolase Defect

Mutation reduces affinity for Vit B-1 in transketolase(No TPP)

Vitamin/coenzyme deficit can make a normal, but essential equilibrium rxn rate limiting. Normal pathway function and control lost.

Malnourished alcoholics
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