TCA Cycle/OXPHOS

Question 1

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

Answer 1

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

Question 2

5 Steps in PDH Complex

Answer 2

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+

Question 3

5 Vitamins/Coenzymes Associated w/ PDH Complex

Answer 3

TPP
Lipoic Acid
CoA
FAD
NAD

Question 4

Regulation of PDH Complex (2)

Answer 4

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

Question 5

3 Activators/1 Inhibitor of PDH Kinase

Answer 5

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

Question 6

Activator of PDH Phosphatase

Answer 6

Ca++

Question 7

1st Step of TCA Cycle

Answer 7

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

Question 8

2nd Step of TCA Cycle

Answer 8

Aconitase isomerizes citrate to isocitrate

Question 9

3rd Step of TCA Cycle

Answer 9

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

Question 10

2 Activators/2 Inhibitors of Isocitrate dehydrogenase

Answer 10

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

Question 11

4th Step of TCA Cycle

Answer 11

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

Question 12

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

Answer 12

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

Question 13

5th Step of TCA Cycle

Answer 13

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

Question 14

6th Step of TCA Cycle

Answer 14

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

Question 15

7th Step of TCA Cycle

Answer 15

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

Question 16

8th Step of TCA Cycle

Answer 16

Malate dehydrogenase converts L-Malate to Oxaloacetate

Generates 3rd NADH

Question 17

4 Oxidation Reactions of TCA Cycle

Answer 17

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

Question 18

Substrate-level Phosphorylation Reaction of TCA Cycle

Answer 18

Succinate thiokinase creates GTP from GDP + inorganic phosphate

Question 19

3 Irreversible Reactions of TCA Cycle

Answer 19

Citrate synthase
Isocitrate dehydrogenase
alpha-ketoglutarate dehydrogenase complex

Question 20

4 AA Entry Points in TCA Cycle (& reason)

Answer 20

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

Question 21

Complex I

Answer 21

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

Question 22

Complex II

Answer 22

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

Question 23

CoQ

Answer 23

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

Question 24

Complex III

Answer 24

Cytochrome bc1, Fe3+ that accepts reduction to Fe2+

Question 25

Cytochrome C

Answer 25

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

Question 26

Complex IV

Answer 26

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

Question 27

Energetic Coupling of OXPHOS (2)

Answer 27

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

Question 28

H+ Pumps

Answer 28

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

Question 29

Difference in NADH/FADH2 ATP # Generation

Answer 29

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)

Question 30

Uncoupled Protons

Answer 30

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