Chapter 9 TCA cycle and Pyruvate Dehydrogenase Complex

Question 1

page 109

Cycle Reactions

1. The first that is condensed with the Acetyl group from AcetylCoA and then regenerated as the cycle is completed ?
2. In this cycle how many carbons enter the cycle and leave as CO₂?
3. Decarboxylation means ?

Answer 1

1. Oxaloacetate OOA
2. two carbons as Acetyl CoA and two leaves as CO₂
3. removing a carbon and leaving as CO₂

Question 2

Acetyl CoA Production

1. What is the major source of AcetylCoA for the TCA cycle ?
2. The end product of aerobic glycolysis ?
3. In the mitochondrial matrix, PDHC converts Pyruvate to ?

Answer 2

1. Oxidative decarboxylation of PYRUVATE by PDHC (Pyruvate Dehydrogenase Complex)
2. Pyruvate
3. AcetylCoA

Question 3

PDHC component Enzymes

1. name all three enzymes involved in Pyruvate conversion ACoA
2. In addition of the enzymes conversion of pyruvate to ACoA, PDHC also contains TWO regulatory enzymes, name two of them.

Answer 3

• E1= Pyruvate Decarboxylase
• E2= Dihydrolipoyl-transacetylase
• E3= Dihydrolipoyl Dehydrogenase

1. Pyruuvate Dehydrogenase Kinase
2. Pyruvate Dehydrogenase Phosphatase

Question 4

Coenzymes

1. How many coenzymes are involved in the PDHC ?
2. Functions of the five coenzymes in PDHC ?
3. What does E1 require for the reaction ?
4. What does E2 require ?
5. What enzyme does FAD and NAD⁺ match with ?

Answer 4

1. five coenzymes
2. Oxidants and carriers for the intermediates of the rxn
3. Thiamine Pyrophosphate (TPP)
4. Lipoic acid
5. E3

Question 5

Two Regulatory Enzymes of PDHC

Pyruvate Dehydrogenase Kinase and Phsophatase

1. what regulatory enzyme PHOSPHORYLATES AND INACTIVATES E1 (Pyruvate decarboxylase)
2. How is E1 phosphorylated in the process and inactivated?
3. when E1 is dephosphorylated it is also ACTIVATED by which regulatory enzyme ?

Key:

Phosphorylate - INctivates E1-Kinase

Dephosphorylate - Activates E1-Phosphatase

Answer 5

1. PDH (KINASE)
2. by regulatory enzyme PDH kinase
3. Pyruvate Dehydrogenase Phosphatase

Question 6

Potent inhibitor of PDH Kinase

Answer 6

Pyruvate

Question 7

CONCEPT to grasp in the PDH regulation enzymes page. 111

1. inactivator of E1
2. high concentrations of pyruvate is a potent inhibitor of PDH Kinase or PDH phosphatase?
3. elevated pyruvate causes activation of
4. What ion is a strong activator of PDH phosphatase ?
5. Rise in the ratios of ATP/ADP, acetyl CoA/CoA and NADH/NAD+
6. In the presence of high energy products (ATP, AcetylCoA and NADH) what happens to the PDHC ?

Answer 7

1. PDH kinase
2. PDH kinase
3. E1
4. Calcium
5. affects enzymatgic activity
6. PDHC is tunred off

Question 8

Defficiency

1. Lactic acidosis is usually cause by
2. The brain relies on ________________cycle for most of its energy
3. the gene defficiency is x linked and affects both ______________?

Answer 8

1. defficiency in the alpha subunits of the E1 tetrameric component of the PDHC
2. TCA cycle
3. male and female

Question 9

what is the intermediate in the TCA cycle ?

Answer 9

citrate

Question 10

page. 112

the source of acetylCoA for the cytosolic syntheis fatty acids

Answer 10

Citrate

Question 11

Page.112 Citrate

1. What is the rate limiting enzyme of glycolysis ?
2. what is another inhibitor for your answer to number 1 ?
3. Activator of AcetylCoA carboxylase ?
4. what is the rate limiting enzyme of fatty acid synthesis ?

Answer 11

1. phosphorfuctokinase - 1
2. Citrate
3. Citrate
4. Acetyl CoA carboxylase