TCA Cycle

Question 1

Where does TCA cycle take place?

Answer 1

Mitochondrial matrix

Question 2

How does pyruvate enter mitochondrion?

Answer 2

Pyruvate, hydroxide anti-transporter

Question 3

How do fatty acids enter mitochondrion?

Answer 3

FACoA transporter

Question 4

What are net products of TCA cycle?

Answer 4

6 NADH, 4 CO2, 2 FADH2, 2 ATP

Question 5

What enzyme converts pyruvate to acetyl CoA?

Answer 5

Pyruvate dehydrogenase

Question 6

What molecules inhibit pyruvate dehydrogenase complex?

Answer 6

Acetyl CoA, NADH (feedback inhibition)

Question 7

How do carbohydrates, fatty acids, and proteins enter the TCA cycle?

Answer 7

Carbs - through glycolysis
Fatty acids - exclusively through acetyl CoA
Proteins - directly enter into TCA cycle

Question 8

What are anaplerotic reactions?

Answer 8

Reactions that produce intermediates for TCA cycle

Question 9

What vitamin is needed to make acetyl CoA? What kind of vitamin is it? What is its deficiency?

Answer 9

Pantatheine - B vitamin - no known deficiency

Question 10

Where is pyruvate converted to acetyl-CoA?

Answer 10

Mitochondrial matrix (pyruvate transporter moves it from cytoplasm into matrix)

Question 11

How is ATP generated in mitochondria exported to cytoplasm?

Answer 11

Specific ATP-ADP exchanger that ensures ADP is brought into mitochondrial matrix and ATP is exported out

Question 12

What’s the pyruvate dehydrogenase complex do?

Answer 12

Oxidizes pyruvate to acetyl-CoA resulting in loss of CO2 and large negative free energy, making it irreversible

Question 13

What cofactors are involved in pyruvate dehydrogenase complex?

Answer 13

NAD, TPP, Lipoic acid, FAD

Question 14

Which cofactor is involved in pyruvate decarboxylase part of PDC? What kind of vitamin is it?

Answer 14

TPP (thiamine pyrophosphate)

B1 vitamin

Question 15

What would a deficiency in TPP cause?

Answer 15

Beriberi, GI symptoms, neurological findings

Question 16

What three enzymes make up PDC?

Answer 16

pyruvate decarboxylase, dihydrolipyl transacetylase, dihydrolipyl dehydrogenase

Question 17

Which enzyme and its cofactor are involved in acetyl group transfer to CoASH and transfer of electrons to riboflavin?

Answer 17

Dihydrolipoyl acetyl transferase and Lipoic Acid

Question 18

Which cofactor accepts electrons from lipoic acid?

Answer 18

FAD

Question 19

What kind of vitamin is NAD? What would a deficiency in niacin or nicotinamide (NAD) cause?

Answer 19

Vitamin B3 - Pellagra skin disease, diarrhea, dementia, ultimately death (in dogs - black tongue)

Question 20

What kind of vitamin is riboflavin? What does a deficiency in riboflavin cause?

Answer 20

B2 vitamin - Fissures in corners of mouth, inflammation of tongue, skin disease, sever irritation of eye

Question 21

What’s the order of cofactors used during PDC rxns?

Answer 21

TPP, lipoic acid, FAD, NAD

Question 22

What enzyme in TCA catalyzes the reaction of oxaloacetate with acetyl-CoA?

Answer 22

Citrate synthase

Question 23

What enzyme in TCA catalyzes the reaction of isocitrate to alpha-ketoglutarate?
What molecules are given off?

Answer 23

isocitrate dehydrogenase; NADH and CO2

Question 24

What enzyme is involved in substrate-level phosphorylation in TCA? It turns ______ into _________ and a ______.

Answer 24

Succinyl-CoA synthetase; it turns succinyl CoA into succinate and a GTP

Question 25

How is TCA cycle regulated by phosphorylation?

Answer 25

Phosphorylated PDH complex is inactive. Dephosphorylated PDH complex is active.

If there is low energy in the cell, Ca2+ will activate phosphatase and PDH activity will increase.

If there is high energy in the cell, ATP-like signals decrease PDH complex activity.

Question 26

Which enzyme generates FADH? Where does the FADH go?

Answer 26

Succinate dehydrogenase

Goes directly to CoQ

Question 27

How much ATP does a single NADH and FADH2 molecule generate?

Answer 27

NADH - 2.5

FADH2 - 1.5

Question 28

How many ATP does one acetyl-CoA generate?

Answer 28

About 12.5 through oxidative phosphorylation including the NADH from PDC

Question 29

What does pyruvate carboylase do? What cofactor is needed for this reaction?

Answer 29

Carboxylation of pyruvate to yield oxaloacetate; requires biotin

Question 30

What pathology is associated with biotin deficiency?

Answer 30

Dermatitis, GI symptoms

Question 31

What low energy signals regulate TCA enzymes?

Answer 31

AMP-like signals

AMP, ADP, NAD, Ca2+, cAMP, CoASH

Question 32

What high energy signals regulate TCA enzymes?

Answer 32

ATP-like signals

ATP, NADH, citrate, acetyl CoA, malonyl-CoA