TCA Cycle/OXPHOS Flashcards Preview

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Flashcards in TCA Cycle/OXPHOS Deck (30)
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1

3 Products of TCA Cycle (& ATP that comes from them) per acetyl-CoA oxidized

3 NADH - 9 ATP
1 FADH2 - 2 ATP
1 GTP - 1 ATP

2

5 Steps in PDH Complex

Pyruvate decarboxylase ejects CO2 from pyruvate and binds it to TPP
Dihydrodrolipoyl transacetylase moves it to oxidized lipoamide
Acetyl group then transferred to CoA to form acetyl CoA
The sulfhydryl (reduced) lipoamide oxidized back to form via FAD-dependent dihydrolipoyl dehydrogenase
FADH2 reoxidized to FAD by dihydrolipoyl dehydrogenase by reducing NAD+

3

5 Vitamins/Coenzymes Associated w/ PDH Complex

TPP
Lipoic Acid
CoA
FAD
NAD

4

Regulation of PDH Complex (2)

PDH Kinase phosphos and inactivates it, while PDH phosphatase activates it

5

3 Activators/1 Inhibitor of PDH Kinase

A: ATP, acetyl-CoA, and NADH (so shut off PDH complex when have high energy)
I: Pyruvate

6

Activator of PDH Phosphatase

Ca++

7

1st Step of TCA Cycle

Citrate synthase joins acetyl-CoA and oxaloacetate to citrate, consuming water and expelling CoA
1st Irreversible step

8

2nd Step of TCA Cycle

Aconitase isomerizes citrate to isocitrate

9

3rd Step of TCA Cycle

Isocitrate dehydrogenase converts isocitrate to alpha-ketoglutarate
1st NADH producing step
1st CO2 expelling step
2nd irreversible step

10

2 Activators/2 Inhibitors of Isocitrate dehydrogenase

I: ATP/NADH
A: ADP/Ca++

11

4th Step of TCA Cycle

alpha-Ketoglutarate dehydrogenase complex converts alpha-ketoglutarate to succinyl-CoA
2nd energy producing step, NADH
2nd CO2 expelling step
Consumes CoA
3rd irreversible step

12

alpha-Ketoglurate dehydrogenase complex (activator, 2 inhibitors, comparison)

Almost identical to PDH complex, including 5 coenzymes (TPP, lipoamide, CoA, FAD, NAD)
A: Ca++
I: NADH, succinyl-CoA

13

5th Step of TCA Cycle

Succinate thiokinase converts succinyl-CoA to succinate
Uses substrate-level phosphorylation to create GTP from inorganic phosphate (VERY uphill)
Expels CoA

14

6th Step of TCA Cycle

Succinate dehydrogenase oxidizes succinate to create a double bond to form fumarate
Produces FADH2

15

7th Step of TCA Cycle

Fumarase adds across fumarate double bond to convert it to L-Malate

16

8th Step of TCA Cycle

Malate dehydrogenase converts L-Malate to Oxaloacetate
Generates 3rd NADH

17

4 Oxidation Reactions of TCA Cycle

Isocitrate, alphaketoglutarate, and malate dehydrogenase - NADH each
Succinate dehydrogenase - FADH2

18

Substrate-level Phosphorylation Reaction of TCA Cycle

Succinate thiokinase creates GTP from GDP + inorganic phosphate

19

3 Irreversible Reactions of TCA Cycle

Citrate synthase
Isocitrate dehydrogenase
alpha-ketoglutarate dehydrogenase complex

20

4 AA Entry Points in TCA Cycle (& reason)

alpha-ketoglutarate
Succinyl-CoA
Fumarate
Oxaloacetate
Enter to go to gluconeogenesis if starving

21

Complex I

NADH Dehydrogenase, forms FMNH2 from FMN via NADH + H+

22

Complex II

Succinate dehydrogenase, forms FADH2 from FAD via conversion of succinate into fumarate

23

CoQ

e- acceptor b/w Complexes I/II and III, accepts from FMNH2 and FADH2 to form CoQH2

24

Complex III

Cytochrome bc1, Fe3+ that accepts reduction to Fe2+

25

Cytochrome C

B/w III and IV, Fe3+ reduced to Fe2+ again

26

Complex IV

Cytochrome c oxidase, Fe3+ to Fe2+ again but then uses it to convert 1/2O2 to H2O

27

Energetic Coupling of OXPHOS (2)

As you go through the chain, the compounds become better oxidizing agents (accepting e-s); the E0 goes from negative to positive

28

H+ Pumps

Complexes I, III, and IV change shape as e-s pass through, pumping H+ from matrix to IM space

29

Difference in NADH/FADH2 ATP # Generation

NADH starts oxphos at Complex I so it hits all 3 pumps (and forms 3 ATP per), FADH2 enters at Complex II so only gets proton pumps from III and IV (and thus 2 ATP per)

30

Uncoupled Protons

Proton leaks uncoupled from ATP synthase allows protons to reenter matrix w/out capturing energy as ATP, generates heat