Pyruvate and TCA cycle

Question 1

What are the 6 sources of pyruvate?

Answer 1

malate, lactate, alanine, glycolysis, serine, cysteine

Question 2

What are the 4 fates of pyruvate?

Answer 2

Oxaloacetate, lactate, alanine, Acetyl CoA

Question 3

What is the major fate of pyruvate?

Answer 3

Acetyl CoA

Question 4

Why would pyruvate avoid going into Oxaloacetate?

Answer 4

Because it requires too much energy

Question 5

If pyruvate can not convert into acetyl CoA, what would be the next best choice?

Answer 5

Lactate or alanine

Question 6

What is the enzyme that converts Pyruvate to Acetyl CoA?

Answer 6

PDH complex

Question 7

Name the co-factors of pyruvate

Answer 7

Tpp, NAD+, FAD, CoA-sh, Lipoic acid

Question 8

Which cofactor is needed for PDH complex?

Answer 8

Lipoic acid

Question 9

Tpp is vitamin __

Answer 9

B1

Question 10

FAD is vitamin___ and also called ___.

Answer 10

B2 and riboflavin

Question 11

CoA-sh is vitamin ___ and also known as ____

Answer 11

B5 and pantothenic acid

Question 12

NAD is vitamin___ and also called ____

Answer 12

B3 and niacin

Question 13

What is PDH complex inhibited by?

Answer 13

ATP and NADH

Question 14

What is the PDH complex activated by?

Answer 14

AMP

Question 15

What happens if TPP is deficient?

Answer 15

Will present with symptoms of PDH complex deficiency

Question 16

Which 2 cycles does PDH complex link?

Answer 16

Glycolysis and TCA

Question 17

In the presence of O2 which cycle does pyruvate go into?

Answer 17

TCA

Question 18

In absence of O2 which cycle does pyruvate go into?

Answer 18

Lactate

Question 19

How many ATP are produced from pyruvate converting to lactate?

Answer 19

2

Question 20

Name the 3 catalytic enzymes of PDH complex

Answer 20

Pyruvate dehydrogenase/decarboxylase (E1)
Dihydrolipolyl transacetylase(E2)
Dihydrolipolyl dehydrogenase(E3)

Question 21

Name the 2 regulatory enzymes of PDH complex

Answer 21

PDH kinase
PDH phosphatase

Question 22

Is PDH complex active or inactive when phosphorylated?

Answer 22

Inactive

Question 23

Is PDH complex active or inactive when dephosphorylated?

Answer 23

Active

Question 24

What brings about dephosphorylation ?

Answer 24

Insulin

Question 25

What does PDH kinase do to the complex?

Answer 25

Inactivate it

Question 26

What inhibits PDH kinase?

Answer 26

ADP and pyruvate

Question 27

What activates PDH kinase?

Answer 27

Acetyl CoA and NADH

Question 28

What does PDH phosphatase do to the complex?

Answer 28

Activate it

Question 29

What activates PDH phosphatase?

Answer 29

Calcium

Question 30

What causes acidosis?

Answer 30

Build up of lactic acid -lactic acid lowers pH

Question 31

What happens if there's an energy deficit of PDH deficiency?

Answer 31

-A deficiency in this enzymatic complex limits the production of Acetyl CoA and thus citrate -Brain problems

Question 32

Which 2 substrates bind to form citrate in the TCA cycle?

Answer 32

Acetyl CoA and OAA

Question 33

Name the four enzymes that bring about production of NADH and FADH2

Answer 33

Malate, alpha-ketoglut, isocitrate, succinate dehydrogenase

Question 34

What is the rate limiting step of TCA cycle?

Answer 34

Isocitrate Dehydrogense

Question 35

Which step in the pathway requires the co-factors used in PDH complex?

Answer 35

Alpha-ketoglutarate dehydrogenase

Question 36

Name another complex where succinyl dehydrogenase is used?

Answer 36

ETC

Question 37

What inhibits and activates Isocitrate dehydrogenase?

Answer 37

Inhibitors: NADH and ATP Activator: ADP

Question 38

What can be used to treat PDH deficiency?

Answer 38

-Cofactor supplementation with thiamine, carnitine, and lipoic acid is the standard of care. - Ketogenic diets (with restricted carbohydrate intake) have been used to control lactic acidosis with minimal success.

Question 39

Which step in the TCA cycle uses GTP?

Answer 39

Succinyl CoA to Succinate

Question 40

What inhibits aconitase?

Answer 40

Flurocitrate

Question 41

How much ATP is produced when 4 dehydrogenases go to the ETC?

Answer 41

9

Question 42

How much ATP is produced from the GTP reaction?

Answer 42

1

Question 43

What inhibits citrate synthase?

Answer 43

Citrate

Question 44

What activates the dehydrogenases?

Answer 44

Calcium

Question 45

What inhibits α-ketoglutarate dehydrogenase?

Answer 45

succinyl CoA and NADH Arsenate

Question 46

What inhibits Succinate dehydrogenase?

Answer 46

OAA

Question 47

Name the 3 enzymes that are inhibited by arsenite poisoning (requires lipoic acid)?

Answer 47

1) Pyruvate dehydrogenase complex, 2) Alpha keto glutarate dehydrogenase complex and 3) Alpha ketoacid dehydrogenase complex.

Question 48

How much ATP is produced overall for the TCA cycle?

Answer 48

20

Question 49

What are the sources of acetyl CoA?

Answer 49

Palmitate, Acetoacetate, Glucose, Pyruvate, Ethanol

Question 50

What's the role of TCA cycle in gluconeogenesis?

Answer 50

TCA cycle intermediates beyond Alpha-ketoglutarate are potentially glucogenic

Question 51

Which amino acids can form acetyl coa?

Answer 51

leucine, lsoleucine, and tyrosine

Question 52

Which amino acids can form fumurate?

Answer 52

phenylalanine and tyrosine

Question 53

Which amino acids can form acetoacetyl coa?

Answer 53

leucine, lysine, tryptophan, tyrosine

Question 54

Which amino acids can form pyruvate?

Answer 54

cysteine, glycine, alanine, hydrox-proline, serine, threonine

Question 55

Which amino acids can form succinyl coa?

Answer 55

Isoleucine, valine, methionine

Question 56

Which amino acids can form alpha-ketoglutarate?

Answer 56

Glutamate, proline, histamine, arginine

Question 57

Which amino acids can form OAA?

Answer 57

arginine and aspartate

Question 58

What's the role of TCA cycle in fatty acid synthesis?

Answer 58

Acetyl CoA is the major substrate for long-chain fatty acid synthesis Acetyl Co A can also be used for the synthesis of cholesterol, steroids etc.

Question 59

Describe the role of TCA cycle in purine and pyrimidine synthesis

Answer 59

1) Succinyl Co A is utilized for Heme synthesis as well as for utilization of ketone bodies. 2) Acetyl Co A is utilized for the synthesis of fatty acids, steroids, cholesterol, ketone bodies as well as Acetyl Choline 3) Glutamic acid is a precursor of GABA, an inhibitory neurotransmitter

Question 60

Why is the TCA cycle termed as amphibolic?

Answer 60

TCA cycle functions in both oxidative and synthetic processes, thus, it is amphibolic

Question 61

What can cause thiamine deficiency?

Answer 61

Chronic alcoholism