Exam 2 - TCA

Question 1

1. What is the standard free energy of: Acetyl CoA + Oxaloacetate = Citrate?
2. What enzyme catalyzes this reaction?

Answer 1

1. -9 Kcal/mol
2. Citrate Synthase

Question 2

What 2 steps release a CO2?

Answer 2

1. Isocitrate –> Alpha-ketoglutarate
2. Alpha-ketoglutarate –> Succinyl CoA

Question 3

What type of enzyme is Succinyl CoA synthetase?

Why?

Answer 3

Ligase

Because it creates bonds to Carbon using ATP/GTP

Question 4

What is the only enzyme from the TCA cycle found in the mitochondria inner membrane?

Answer 4

Succinate Dehydrogenase

Question 5

1. What enzyme catalyzes Fumarate –> Malate
2. What type of enzyme is this?
3. What is this reaction’s Free energy value

Answer 5

1. Fumarase
2. Lyase
3. +/- 0 ==> Freely reversible

Question 6

What is the free energy value for Succinate –> Fumarate?

Answer 6

+/- 0 ==> freely reversible

Question 7

1. What enzyme catalyzes the reaction: Alpha-ketoglutarate –> Succinyl CoA?
2. What type of enzyme is this>
3. What is the free energy value of this reaction?
   
   1. What enzyme does this reaction closely resemble (Hint: not in TCA)

Answer 7

1. Alpha-ketoglutarate Dehydrogenase
2. Oxidoreductase
3. -8 kcal/mol
   
   1. Pyruvate dehydrogenase

Question 8

1. What enzyme catalyzes the reaction: Isocitrate –> Alpha-ketoglutarate?
2. What type of enzyme is this?
3. What is this reaction’s free energy value?

Answer 8

1. Isocitrate dehydrogenase
2. Oxidoreductase
3. -5 kcal/mol

Question 9

Why type of enzyme is Aconitase?

Answer 9

Lyase

Question 10

1. What enzyme catalyzes the reaction: Citrate –> Isocitrate?
2. What type of enzyme is this?
3. What is the free energy value of this reaction?

Answer 10

1. Aconitase
2. Lyase
3. +/- 0 => Freely reversible

Question 11

1. What enzyme catalyzes the reaction: Malate –> Oxaloacetate>
2. What type of enzyme is this?
3. What is the free energy value of this reaction?

Answer 11

1. Malate Dehydrogenase
2. Oxidoreductase
3. +6 Kcal/mole!!

Question 12

In what step of the TCA cycle is a GTP made?

Answer 12

Succinyl Coa –> Succinate

Question 13

How many NADH and FADH2 are made form TCA cycle?

Answer 13

• NADH - 3
• FADH2 - 1

Question 14

At what steps are NADHs made during the TCA cycle?

Answer 14

1. Isocitrate –> Alpha-ketoglutarate
2. Alpha-ketoglutarate –> Succinyl CoA
3. Malate –> Oxaloacetate

Question 15

At what step is FADH2 made in the TCA cycle?

Answer 15

1. Succinate –> Fumarate

Question 16

What is the difference between Cataplerotic and Anaplerotic?

Answer 16

• Cataplerotic - breaking carbon stuff down
• Anaplertoic - building things with carbon backbone molecules

Question 17

What amino acids are precursors to the following TCA cycle intermediates?

• Acetyl CoA
• Pyruvate
• Oxaloacetate
• Fumarate
• Succinyl CoA
• Alpha - ketoglutarate

Answer 17

• Acetyl CoA - Leucine
• Pyruvate - alanine
• Oxaloacetate - aspartate
• Fumarate - Phenyl alanine, Tyrosine
• Succinyl CoA - Valine and isoleucine (branched carbon backbones) —> Propionyl CoA
• Alpha - ketoglutarate - Deaminate Glutamine –> Glutamate

Question 18

How many ATPs do the following high energy molecules “create/are worth?”

NADH

FADH2

Acetyl-CoA

Answer 18

1. NADH - 2.5 ATP
2. FADH2 - 1.5 ATP
3. Acetyl-CoA - 10 ATP

Question 19

CoA is a [] carrier molecule

Answer 19

Aceyl group

Question 20

What enzyme takes pyruvate and makes Acetyl CoA?

Answer 20

Pyruvate Dehydrogenase

Question 21

Using Oxygen, what are 3 end-products of pyruvate?

Answer 21

1. Alanine (from transamination)
2. Oxaloacetate (from carboxylation)
3. Acetyl CoA (from oxidate decarboxylation)

Question 22

What is the standard free energy value for Pyruvate –> Acetyl CoA?

Answer 22

-8 kcal/mol

Question 23

1. What enzyme catalyzes: Pyruvate –> Acetyl CoA?
2. What type of “reaction” is this?
3. What 3 cofactors are required?

Answer 23

1. pyruvate dehydrogenase
2. Oxidative decarboxylation
3. Thiamine, Lipoamide, FAD+

Question 24

1. What does pyruvate dehydrogenase kinase do?
2. What does pyruvate dehydrogenase phosophatase do?

Answer 24

1. Phosphorylates PDH causing it to be less active
2. Dephosphorylates PDH causing it to be more active

Question 25

What are the 3 fates of pyruvate in the presence of Oxygen?

Answer 25

1. Transamination to **Alanine** 2. Carboxylation to **Oxaloacetate** 3. Oxidateve decarboxylation to **Acetyl CoA**

Question 26

What are the 2 fates of Pyruvate in the abscence of Oxygen?

Answer 26

1. Ethanol 2. Reduced to **Lactate**

Question 27

What three cofactors are need for pyruvate dehydrogenase to take pyruvate and form Acetyl CoA?

Answer 27

1. Thiamine pyrophosphate 2. Lipamide 3. FAD+

Question 28

Which enzyme Inactivates PDH and which enzyme activates PDH?

Answer 28

* Pyruvate Dehydrogenase Kinase - inactivates * Pyruvate dehydrogenase Phosophatase - activates

Question 29

What are the cofactors that increase the activity level of PDH Phosphatase?

Answer 29

Mg2+ Ca 2+

Question 30

What 2 molecules positively affect _PDH Kinase_ activity?

Answer 30

* NADH * Acetyl CoA

Question 31

What 4 molecules negatively affect PDH Kinase activity?

Answer 31

1. CoASH 2. NAD+ 3. ADP 4. Pyruvate

Question 32

In Cataplerotic processes what happens to the following TCA intermediates? 1. Oxaloacetate - 2. Citrate - 3. Alpha-ketoglutarate - 4. Succinyl CoA - 5. Malate -

Answer 32

1. Oxaloacetate - a**mino acid synthesis** 2. Citrate - **fatty acid syn and sterol syn** 3. Alpha-ketoglutarate - **amino acid syn** 4. Succinyl CoA - **heme syn** 5. Malate - **gluconeogenesis**

Question 33

Pyruvate is used by this enzyme, [] , to form oxaloacetate

Answer 33

Pyruvate Carboxylase