TCA Cycle

Question 1

Four fates of pyruvate

Answer 1

1) lactate (under anaerobic conditions)
2) alanine (amino acid synthesis)
3) acetyl CoA (citric acid cycle)
4) oxaloacetate (anaplerotic reaction to replenish TCA intermediates)

Question 2

What is acetyl-coA oxidized to in the citric acid cycle

Answer 2

CO2

Question 3

Enzyme responsible for conversion of pyruvate to acetyl-CoA

Answer 3

pyruvate dehydrogenase

Question 4

Five coenzymes used by pyruvate dehydrogenase complex

Answer 4

1) Thiamine pyrophosphate
2) lipoyllysine
3) FAD
4) NAD+
5) CoA-SH

Question 5

Riboflavin (Vit B2) deficiency can cause what condition with chapped/fissured lips

Answer 5

Cheilosis

Question 6

Pellagra is a deficiency in…

Answer 6

Niacin (B3)

Question 7

Net Inputs into the Citric Acid Cycle (6)

Answer 7

1) Acetyl-Coa
2) 3 NAD+
3) FAD
4) GDP
5) Pi
6) 2 H2O

Question 8

Net Outputs from the Citric Acid Cycle (6)

Answer 8

1) 2 CO2
2) 3 NADH
3) FADH2
4) GTP
5) CoA
6) 3 H+

Question 9

In this anaplerotic reaction, pyruvate forms oxaloacetate via which enzyme

Answer 9

pyruvate carboxylase

Question 10

Enzyme responsible for pyruvate to malate conversion

Answer 10

Malic enzyme

Question 11

Converts PEP to oxaloacetate.

Answer 11

PEP carboxykinase

Question 12

Besides glycolysis products, what else can be a source for TCA cycle intermediates?

Answer 12

glucogenic amino acids

Question 13

Tissue specificity of pyruvate carboxylase

Answer 13

Liver and kidney

Question 14

Tissue specificity of PEP carboxykinase

Answer 14

Heart and skeletal muscle

Question 15

Tissue specificity of PEP carboxylase

Answer 15

Higher plants, yeast, bacteria (we aint got it?)

Question 16

Tissue specificity of malic enzyme

Answer 16

Trick question, it’s pretty widespread

Question 17

Three highly thermodynamically favorable and irreversible steps of the TCA cycle

Answer 17

1) pyruvate dehydrogenase
2) isocitrate dehydrogenase
3) alpha-ketoglutarate dehydrogenase

Question 18

When these three ratios are high, the citric acid cycle is allosterically inhibited. Indicates an energy-sufficient metabolic state.

Answer 18

1) ATP/ADP
2) NADH/NAD+
3) Acetyl-CoA/CoA

Question 19

The rate of flow through the citric acid cycle can be limited by the availability of citrate synthase substrates. What are they?

Answer 19

oxaloacetate and acetyl-CoA

Question 20

Feedback inhibition is done by what three molecules in the citric acid cycle

Answer 20

succinyl-CoA, citrate, and ATP

Question 21

What stimulates energy-yielding metabolism of the TCA cycle in muscle tissue

Answer 21

Ca2+ (its levels increase during muscle contraction… right…)

Question 22

Positive regulators of pyruvate dehydrogenase (4)

Answer 22

AMP, CoA, NAD+, Ca2+

Question 23

Negative regulators of pyruvate dehydrogenase (4)

Answer 23

ATP, acetyl-CoA, NADH, fatty acids

Question 24

Positive regulators of citrate synthase (1)

Answer 24

ADP

Question 25

Negative regulators of citrate synthase (4)

Answer 25

NADH, succinyl-CoA, citrate, ATP

Question 26

Positive regulators of isocitrate dehydrogenase (2)

Answer 26

Ca2+, ADP

Question 27

Negative regulators of isocitrate dehydrogenase (1)

Answer 27

ATP

Question 28

Positive regulators of alpha-ketoglutarate dehydrogenase (1)

Answer 28

Ca2+

Question 29

Negative regulators of alpha-ketoglutarate dehydrogenase (2)

Answer 29

succinyl-CoA, NADH