TCA cycle

Question 1

how much energy do pyruvates have before TCA cycle and ox phosphorylation?

Answer 1

90%

Question 2

where does TCA occur?

Answer 2

matrix

exported to cytosolic space by transporters

Question 3

describe outer membrane

inner?

Answer 3

has porins to allow compounds to to pass

inner: higher impermeable. transport protein carriers transport specific substrates

Question 4

what goes in and out of TCA?

Answer 4

in: CoA
3NAD+
FAD
GDP
Pi
2H2o

out: 
2co2
3NADH
FADH2
Co-ASH
GTP
2H+

Question 5

is TCA neg or pos delta G?

Answer 5

delta G = -33kj/mol

Question 6

overall TCA rxn?

Answer 6

• pyruvate made in ctyosol
• enters mitochondria
• decarboxylation
• coupled to CoA
• NADH production

Question 7

describe pyruvate dehydrogenase complex

3 subunits on inner membrane?

Answer 7

catalyzes pyruvate to CoA (oxidative decarboxylation)

subunits:

1. pyruvate dehydrogenase (E1) = pyruvate decarboxylate
2. dihydrolipoyl transacetylase (E2) = CoASH transfer
3. dihydrolipoyl dehydrogenase (E3) = reoxidize dihydrolipoamide

Question 8

describe E1 coenzyme in pyruvate dehydrogenase complex

Answer 8

TPP (thiamine pyrophosphate)

• has highly acidic H+ on thiazollum ring which catalyzes the rxn
• carbanion attacks pyruvate to cause decarbox rxn

Question 9

describe E2 coenzyme in pyruvate dehydrogenase complex

Answer 9

Lipoic acid: disulfide bond becomes SH bond

Coenzyme A (CoASH): after decarbox rxn = rxn with acetyl group forms thioester bond

Question 10

describe E3 coenzyme in pyruvate dehydrogenase complex

Answer 10

NADH and FADH2

• high E e carriers
• nicotiamide end of NAD+ catalyzes reduction

requires 2H+ and 2e- :
NAD to NADH
FAD to FADH2
FMN to FMNH2

Question 11

describe rxn mechanism for pyruvate dehydrogenase

what is the rate limiting rxn?

Answer 11

refer to notebook

rate limiting:

• in the 1st step (pyruvate decarboxylase)
• carbanion attacks TTP –> release of co2

Question 12

what do anaplerotic rxns do?

Answer 12

replenished intermediates of TCA so intermediates concentratino stay constant

catalyzed by pyruvate carboxylase

requires ATP

Question 13

describe TCA regulation

enzymes used?

what inhibits and activates them?

Answer 13

1. citrate synthase
   - oxaloacetate + acetyl = citrate
   - inhibited by: succ-CoA, citrate, ATP, NADH
2. isocitrate dehydrogenase
   - citrate = isocitrate = alpha ketoglutarate
   - inhibited by: high ATP and NADH
   - activated by: high ADP and NAD+
3. alpha ketoglutarate dehydrogenase
   - inhibited by: nigh NADH and succinyl coa
   - activated by high AMP