Lecture 36

Question 1

What is the rate-limiting step of the citric acid cycle?

Answer 1

Because it is a cyclic process it doesn’t have a rate-limiting step

Question 2

What is the rate of the CAC affected by?

Answer 2

• NAD+/NADH ratio
• Regulated enzyme
• Concentrations of intermediated

Question 3

Which enzymes of the CAC are regulated?

Answer 3

• Isocitrate dehydrogenase

* alpha-ketoglutarate dehydrogenase

Question 4

What kind of reactions do the regulated enzymes of the CAC catalyze?

Answer 4

Oxidative decarboxylations

Question 5

What are the inhibitors of the CAC?

Answer 5

NADH and ATP

Question 6

What are the Activators of the CAC?

Answer 6

ADP and Ca2+

Question 7

What regulates Citrate Synthase?

Answer 7

Citrate through product inhibition, but not at physiological conditions

Question 8

What is Isocitrate dehydrogenase inhibited by?

Answer 8

• NADH

* ATP

Question 9

What kind of inhibitor is NADH to isocitrate dehydrogenase?

Answer 9

Allosteric effector

Question 10

What is Isocitrate Dehydrogenase activated by?

Answer 10

ADP

Question 11

What inhibits alpha-ketoglutarate dehydrogenase?

Answer 11

• NADH

* Succinyl CoA (product inhibition)

Question 12

What activates alpha-ketoglutarate dehydrogenase?

Answer 12

Calcium

Question 13

Is the CAC catabolic and anabolic?

Answer 13

It is Amphibolic so its both

Question 14

What can citrate be used to make outside of the CAC?

Answer 14

Fatty acids

Question 15

What can alpha-ketoglutarate be used to make outside of the CAC?

Answer 15

Glutamate

Question 16

What can oxaloacetate be used to make outside of the CAC?

Answer 16

Aspartate and carbohydrates

Question 17

What can the CAC intermediates be used to make?

Answer 17

• Carbohydrates
• Fats
• Nucleotides

Question 18

What are Anapleurotic Reactions?

Answer 18

Reactions that replenish intermediates in a cyclic metabolic pathway

Question 19

What is the important Anaplerotic reaction in the CAC?

Answer 19

The reaction catalyzed by pyruvate carboxylase that converts pyruvate to oxaloacetate

Question 20

How many carbons is acetyl-CoA?

Answer 20

A 2 carbon compound

Question 21

What does PDH catalyze?

Answer 21

The conversion of pyruvate into acetyl-CoA

Question 22

How many carbons is Oxaloacetate?

Answer 22

4 carbons

Question 23

What kind of reaction is making oxaloacetate from pyruvate?

Answer 23

A carboxylation because pyruvate is 3C and oxaloacetate is 4C

Question 24

What are the products and reactants of the conversion of Pyruvate to Oxaloacetate by pyruvate carboxylase?

Answer 24

Reactants: CO2, ATP
Products: ADP, Pi

Question 25

What does Pyruvate Carboxylase catalyze?

Answer 25

The conversion of Pyruvate to Oxaloacetate

Question 26

What catalyzes the conversion of Pyruvate to Oxaloacetate?

Answer 26

Pyruvate Carboxylase

Question 27

What is acetyl-CoA an inhibitor for?

Answer 27

PDH

Question 28

What is an activator of pyruvate carboxylase?

Answer 28

Acetyl-CoA

Question 29

What inhibits and activates Pyruvate Carboxylase?

Answer 29

Acetyl-CoA activates it and ADP inhibits it

Question 30

How many ATP does the CAC produce for every acetyl-CoA and what is the breakdown?

Answer 30

10 ATP for every acetyl-CoA that comes in as citrate. •7.5 ATP from the 3 NADH •1.5 ATP from FADH2 •1 GTP

Question 31

What is the P:O ratio of NADH?

Answer 31

2.5

Question 32

What is the P:O ratio of FADH2?

Answer 32

1.5

Question 33

How many ATP does complete oxidation of glucose yield?

Answer 33

32 ATP

Question 34

How many ATP does anaerobic glycolysis produce net?

Answer 34

2 ATP

Question 35

What is the increase in ATP production in anaerobic vs aerobic glycolysis?

Answer 35

Anaerobic glycolysis produces 2 ATP while glycolysis, the PDH rxn and the CAC produces 32 which is 16 fold

Question 36

How many ATP are produced in glycolysis and the ETC?

Answer 36

* Because 2 NADH are produced in glycolysis that can be used to make 5 ATP * 2 ATP are also produced in the payoff phase of glycolysis

Question 37

How many ATP are produced from the PDH reaction?

Answer 37

2 NADH from the conversion of Pyruvate to Acetyl-CoA to produce 5 ATP

Question 38

How many NADH are produced in the CAC?

Answer 38

6

Question 39

How many FADH2 are produced in the CAC?

Answer 39

2

Question 40

How many GTP are produced in the CAC?

Answer 40

2

Question 41

How many ATP are produced in the CAC from the ETC and GTP?

Answer 41

20

Question 42

How is a lactate a fuel under metabolic conditions?

Answer 42

It can be converted to pyruvate (producing NADH) which can be converted to acetyl CoA and can be oxidized in the CAC

Question 43

Why would cells consume less glucose in the presence of oxygen (Pasteur environment)

Answer 43

The cells are getting more ATP for every glucose oxidized