PDH & TCA

Question 1

Where does TCA occur?

Answer 1

mitochondrial matrix

Question 2

function of TCA cycle

Answer 2

oxidation of acetyl CoA & participation in biosynthetic reactions

Question 3

oxidation of acetyl CoA

Answer 3

metabolism of amino acids, fatty acids, and carbohydrates into CO2 + H2O; accounts for 2/3 of total O2 consumption and ATP production

Question 4

What biosynthetic reactions does TCA play a part in?

Answer 4

formation of glucose from carbon skeletons of AAs and provides building blocks for heme synthesis

Question 5

How much ATP can be generated from aerobic glycolysis + TCA?

Answer 5

38

Question 6

How much ATP can be generated from anaerobic glycolysis?

Answer 6

only 2; no TCA

Question 7

CoA

Answer 7

carrier of acetyl

Question 8

acetyl group

Answer 8

CH3-C=O

Question 9

outer membrane of mitochondria

Answer 9

contains porins that permit free diffusion of small molecules

Question 10

inner membrane of mitochondria

Answer 10

contains transport proteins that control passage of metabolites such as ATP, ADP, pyruvate, Ca++, and phosphate; also contains coenzymes for ETC

Question 11

mitochondrial matrix

Answer 11

contains enzymes of TCA cycle; fatty acid oxidation enzymes, ribosomes

Question 12

pyruvate dehydrogenase complex

Answer 12

multimolecular complex located in mitochondrial matrix

Question 13

function of PDH complex

Answer 13

converts pyruvate into acetyl-CoA for the TCA cycle

Question 14

component enzymes of PDH

Answer 14

1. pyruvate decarboxylase (E1)
2. dihydrolipoyl transacetylase (E2)
3. dihydrolipoyl dehydrogenase (E3)

Question 15

component coenzymes of PDH

Answer 15

1. thiamine pyrophosphate
2. lipoic acid
3. coenzyme A (CoA)
4. flavin adenine dinucleotide (FAD)
5. nicotinamide adenine dinucleotide (NAD+)

Question 16

thiamine pyrophosphate (TPP)

Answer 16

E1-bound

Question 17

lipoic acid

Answer 17

E2-linked

Question 18

coenzyme A

Answer 18

E2-substrate

Question 19

FAD

Answer 19

E3-bound

Question 20

NAD+

Answer 20

E3-substrate

Question 21

key coenzyme in PDH

Answer 21

thiamine pyrophosphate

Question 22

Beriberi

Answer 22

clinical manifestation of thiamine deficiency that affects high-energy requiring tissues in the CV and CNS

Question 23

Beriberi risk factors

Answer 23

diet consisting largely of white rice and alcholism

Question 24

overall reaction of PDH

Answer 24

pyruvate + CoA + NAD+ –> acetyl-CoA + CO2 + NADH

Question 25

kinase effect on PDH

Answer 25

phosphorylates PDH, inactivating it

Question 26

What stimulates kinase to phosphorylate PDH?

Answer 26

increase in acetyl CoA/CoA ration or NADH/NAD+ ratio (more products)

Question 27

phosphatase effect on PDH

Answer 27

dephosphorylates PDH, activating it

Question 28

What stimulates phosphatase to dephosphorylate PDH?

Answer 28

increase in ADP/ATP ratio (also inhibits kinase)

Question 29

TCA cycle

Answer 29

acetyl CoA + oxaloacetate --> citrate --> isocitrate --> alpha-ketoglutarate --> succinyl-CoA --> succinate --> fumarate --> malate --> oxaloacetate

Question 30

acetyl CoA + oxaloacetate --> citrate

Answer 30

aldol condensation; H2O to CoA

Question 31

citrate --> isocitrate

Answer 31

isomerization

Question 32

isocitrate --> alpha-ketoglutarate

Answer 32

oxidation & decarboxylation; NAD+ to NADH + H+ and CO2

Question 33

alpha-ketoglutarate --> succinyl CoA

Answer 33

oxidation and decarboxylation; NAD+ to NADH + H+ and CO2

Question 34

succinyl-CoA --> succinate

Answer 34

cleavage of thioester; GDP to GTP and CoA

Question 35

succinate --> fumarate

Answer 35

oxidation; FAD to FADH2

Question 36

fumarate --> malate

Answer 36

hydration

Question 37

TCA cycle overall reaction

Answer 37

acetyl CoA + 3NAD+ + FAD + GDP + Pi + H2O --> 2 CO2 + 3NADH + FADH2 + GTP + 3H+ + CoA

Question 38

malate --> oxaloacetate

Answer 38

oxidation; NAD+ to NADH + H+

Question 39

How many electrons transferred during TCA?

Answer 39

4 total; three from reducing NAD+ to NADH and 1 from FAD to FADH2

Question 40

TCA products

Answer 40

2 CO2, 1 FADH2, 3NADH, and 1GTP

Question 41

each NADH can produce _ ATP

Answer 41

3; so 9 total each cycle

Question 42

each FADH2 can produce _ ATP

Answer 42

2

Question 43

TCA cycle is regulated by _

Answer 43

substrate availability, product inhibition, and competitive feedback inhibition by cycle intermediates

Question 44

substrate availability _ regulates citrate synthetase

Answer 44

positively; acetyl-CoA & oxaloacetate

Question 45

product availability _ regulates citrate synthetase

Answer 45

negatively; NADH

Question 46

cycle intermediates _ TCA cycle

Answer 46

inhibit

Question 47

positive allosteric regulators of TCA cycle

Answer 47

ADP & Ca++

Question 48

ADP

Answer 48

levels increase with muscular contraction, biosynthetic reactions; activates isocitrate dehydrogenase

Question 49

Ca++

Answer 49

activates PDH to make acetyl-CoA; activates isocitrate dehydrogenase & alpha-ketoglutarate dehydrogenase

Question 50

amphibolic

Answer 50

process that is both catabolic and anabolic --> the TCA cycle

Question 51

How is TCA cycle amphibolic?

Answer 51

catabolic: acetyl-CoA oxidation for ATP generation anabolic: biosynthetic pathways use TCA intermediates

Question 52

malate

Answer 52

transported out of mitochondria and converted to oxaloacetate for gluconeogenesis

Question 53

citrate

Answer 53

citrate from citrate synthetase is exported to cytosol and converted back to acetyl-CoA for fatty acid and cholesterol biosynthesis

Question 54

alpha-ketoglutarate

Answer 54

used to make glutamate

Question 55

succinyl-CoA

Answer 55

starting material for porphyrin (heme) biosynthesis