Pyruvate Metabolism & TCA Cycle

Question 1

What is the function of mitochondria?

Answer 1

• beta-oxidation of fatty acids
• produce ATP using oxidative phosphorylation

Question 2

How does pyruvate become Alanine?

Answer 2

transamination via Ala aminotransferase

Question 3

How does pyruvate become Oxaloacetate?

Answer 3

carboxylation via pyruvate carboxylase & biotin

Question 4

How does pyruvate become Acetyl CoA?

Answer 4

oxidative decarboxylation via PDC

Question 5

How does pyruvate become lactate?

Answer 5

reduction via lactate dehydrogenase

Question 6

Where does the TCA cycle occur?

Answer 6

mitochondrial matrix

Question 7

Where does glycolysis occur for the TCA cycle?

Answer 7

in cytosol of cell

Question 8

What are the 3 enzyme complexes in the pyruvate dehydrogenase (PDH) complex?

Answer 8

1. pyruvate dehydrogenase
2. dihydrolipoyl transacetylase -> Acetyl CoA
3. dihydrolipoyl dehydrogenase -> NADH + H

Question 9

What is the lipoic acid prosthetic group?

Answer 9

transfers pyruvate between enzymes until it becomes acetyl CoA

Question 10

What activates the PDH complex?

Answer 10

1. pyruvate dehydrogenase phosphatase
2. pyruvate
3. insulin
4. Ca 2+

Question 11

What inactivates the PDH complex?

Answer 11

1. pyruvate dehydrogenase kinase
2. ATP
3. NADH
4. acteyl CoA

all activate PDK

Question 12

Where can Acetyl CoA be used?

Answer 12

• TCA cycle
• ketone bodies
• sterols & fatty acids

Question 13

What is the net energy production of the TCA cycle?

Answer 13

1 GTP

Question 14

How much NADH & FADH is produced in the TCA cycle?

Answer 14

3 NADH & 1 FADH

Question 15

What is the high energy molecule of TCA cycle?

Answer 15

succinyl CoA attached to the membrane

Question 16

What are the 3 irreverisble/regulated steps of the TCA cycle?

Answer 16

1. citrate synthase
2. isocitrate dehydrogenase
3. alpha-ketoglutarate dehydrogenase complex

Question 17

What is the rate limiting step of the TCA cycle?

Answer 17

isocitrate dehydrogenase

Question 18

What activates TCA cycle regulation?

Answer 18

• ADP
• Ca 2+

Question 19

What inhibits TCA cycle regulation?

Answer 19

• ATP
• NADH
• citrate
• succinyl CoA

Question 20

In the TCA cycle, what can oxaloacetate be used for?

Answer 20

amino acid synthesis

Question 21

In the TCA cycle, what can citrate be used for?

Answer 21

fatty acid synthesis

Question 22

In the TCA cycle, what can malate be used for?

Answer 22

gluconeogenesis

Question 23

In the TCA cycle, what can succinyl CoA be used for?

Answer 23

heme synthesis

Question 24

In the TCA cycle, what can alpha-ketoglutarate be used for?

Answer 24

amino acid synthesis & neurotransmitter

Question 25

In the anaplerotic reaction of the TCA cycle, how can pyruvate be converted to oxaloacetate?

Answer 25

using pyruvate carboxylase & biotin

Question 26

In the anaplerotic reaction of the TCA cycle, how can alpha-ketoglutarate be formed?

Answer 26

amino acids -> glutamate

Question 27

In the anaplerotic reaction of the TCA cycle, how can succinyl CoA be formed?

Answer 27

valine & isoleucine -> propionyl CoA

Question 28

In the TCA cycle, what is pyruvate dehydrogenase deficiency?

Answer 28

• leads to chronic lactic acidosis due to increased pyruvate & lactate
• severe neurological defects
• treatment: ketogenic diet

Question 29

In the TCA cycle, what is fumarase deficiency?

Answer 29

• elevated fumarate & succinate
• severe neurological impairment

Question 30

What can TCA cycle dysfunction lead to?

Answer 30

encephalopathies & certain types of cancer