L 24: TCA cycle

Question 1

What type of reactions are required during states of low energy?

Answer 1

Anaplerotic reactions

Question 2

The citric acid cycle is a source of ?

Answer 2

Biosynthetic precursors

Question 3

By what 2 ways is Pyruvate Dehydrogenase Complex (PDH or PDC) regulated

Answer 3

Allosterically

Phosphorylation

Question 4

How many carbon units does the citric acid cycle oxidize?

Answer 4

TWO

Question 5

True or false

Entry into the citric acid cycle and metabolism through it are not highly controlled

Answer 5

False, Both are high controlled

Question 6

The citric acid cycle takes place where?

Answer 6

Mitochondria

Question 7

The oxidation of 2-carbon units to produces what?

Answer 7

• 2 CO2 molecules
• 1 GTP
• High energy electrons in the form of NADH and FADH2

Question 8

Acetyl CoA is obtained from what three energy nutrients?

Answer 8

Carbohydrates
Lipids
Proteins

Question 9

What is the activated form of acetate?

Answer 9

Acetyl CoA

Question 10

What are the 3 steps of Acetyl CoA from pyruvate

Answer 10

• Decarboxylation
• Oxidation
• Transfer acetyl group to coenzyme A

Question 11

Steps for Aerobic Glycolysis chain oxidative phosphorylation (pyruvate entering mitochondria)

Answer 11

1. Pyruvate must enter mitochondria
2. Pyruvate utilize mitochondrial pyruvate carrier (MPC)
3. Pyruvate dehydrogenase complex (PDC) catalyzes the decarboxylation of pyruvate

Question 12

What 3 enzymes are required in the pyruvate dehydrogenase reaction

Answer 12

E1,E2,E3

Question 13

What 5 coenzymes are required in the pyruvate dehydrogenase reaction

Answer 13

Catalytic factor:
*Thiamine pyrophosphate TPP
* Lipoic acid
*FAD
Stoichiometric cofactors
*CoA
*NAD+

Question 14

What does the Pyruvate Dehydrogenase Complex do?

Answer 14

Catalyzes the decarboxylation of pyruvate into:

Acetyl CoA+Co2+NADH+H

Question 15

High Acetyle CoA directly inhibits what?

Answer 15

E2 by phosphorylation

Question 16

When regulating PDC the accumulation of ADP and pyruvate activate what?

Answer 16

Phosphatases

Question 17

All energy containing nutrients should be converted to what?

Answer 17

Acetyl CoA

Question 18

TCA occurs under what type of conditions?

Answer 18

Aerobic

Question 19

True or False

TCA produces more energy from glucose than glycolysis?

Answer 19

True

Question 20

What links glycolysis to the TCA?

Answer 20

Pyruvate dehydrogenase (PDH)

Question 21

The first step of the TCA cycle does what?

Answer 21

Condensation of 4-carbon oxaloacetate and 2-carbon acetyl group of acetyl CoA

Question 22

What enzyme catalyzes Oxaloacetate to Citrate

Answer 22

Citrate synthase

Question 23

What enzyme isomerizes citrate to isocitrate

Answer 23

Aconitase moves OH atom via dehydration/hydration rxn

Question 24

What enzyme completes the first oxidation-reduction rxn of isocitrate to Alpha-Ketoglutarate

Answer 24

Isocitrate dehydrogenase

Question 25

What is the unstable intermediate formed by the rxn of Isocitrate and isocitrate dehydrogenases?

Answer 25

Oxalosuccinate

Question 26

What is the rate limiting step of the TCA cycle?

Answer 26

Isocitrate to Alpha-ketoglutarate

Question 27

What enzyme catalyzes Alpha-ketoglutarate to succinyl CoA?

Answer 27

Alpha-ketoglutarate dehydrogenase

Question 28

What step yields a high energy phopho-transfer compound (GTP,ATP)?

Answer 28

Succinyl CoA to Succinate

Question 29

What enzyme completes the rxn between Succinyl CoA and Succinate?

Answer 29

Succinyl CoA synthetase

Question 30

What enzyme catalyzes formation of furmate while generating FADH2?

Answer 30

Succinte dehydrogenase

Question 31

FADH2 is not actually released from the enzyme, but electrons are passed directly to ______ in the _____ ______ ______.

Answer 31

Co-Q | electron transport chain

Question 32

What enzyme is directly associated with the ETC (complex-II) located in the inner mitochondrial membrane?

Answer 32

Succinate dehydrogenase

Question 33

What Catalyzes the hydration of Fumarate to form L-Malate?

Answer 33

Fumarase

Question 34

what enzyme oxidizes malate to form oxaloacetate?

Answer 34

Malate dehydrogenase

Question 35

The final step of the TCA L-malate to Oxaloacetate is driven by the use of what 2 products?

Answer 35

* Oxaloacetate-citrate synthase | * NADH- electron transport chain

Question 36

High _____ _____ directly inhibits PDH complex subunits E2

Answer 36

Acetyl CoA

Question 37

What dictates PDH complex activity?

Answer 37

Energy charge of the cell

Question 38

What are the 3 control site of TCA regulation

Answer 38

1. Citrate synthase 2. Isocitrate dehydrogenase 3. alpha - ketogluturate dehydrogenase

Question 39

What complex is very similar to PDH?

Answer 39

Alpha - ketogluturate dehydrogenase

Question 40

What are the 2 major anaplerotic reactions?

Answer 40

1. Degradation of amino acids | 2. Carboxylation of Pyruvate

Question 41

What can stimulate FA synthesis by activating phosphatases and increasing conversion of pyruvate to acetyl CoA?

Answer 41

Insulin

Question 42

Allosteric activators of Pyruvate dehydogenase complex via activation of PDP

Answer 42

Ca, Mg

Question 43

PDC activators via Inhibition of PDK

Answer 43

ADP,CoA,NAD, pyruvate

Question 44

Inhibitors of PDC via allosteric activation of PDK?

Answer 44

Acetyl CoA, NADH

Question 45

Inhibitors of PDC via PDK activation

Answer 45

Acetyl CoA, ATP

Question 46

What does Arsenite do?

Answer 46

Inhibits PDC by binding to lipoic acid in E2

Question 47

Anaplerotic reactions are required during state of _____ energy.

Answer 47

Low