Reactions of citric acid cycle

Question 1

What is the first reaction of the citric acid cycle

Answer 1

1. acetyl CoA and oxaloacetate convert to citrate
2. Citrate synthase
3. Condensation

Question 2

What is the second reaction of the citric acid cycle

Answer 2

1. Citrate converts to isocitrate
2. Aconitase
3. Converts tertiary alcohol to secondary
4. First dehydration then hydration

Question 3

What is the third reaction of the citric acid cycle

Answer 3

1. Isocitrate to 2-oxoglutarate
2. Isocitrate dehydrogenase
3. First isocitrate is oxidised to oxalosuccinate coupled with reduction of NAD+ to NADH
4. Then oxalosuccinate is decarboxylated producing 2-oxoglutarate and CO2

Question 4

What is the fourth reaction of the citric acid cycle

Answer 4

1. 2-oxoglutarate is decarboxylated to succinyl-coenzyme A
2. 2-oxoglutarate dehydrogenase
3. Reduction of NAD+ to NADH and production of CO2

Question 5

What is the fifth reaction of the citric acid cycle

Answer 5

1. Succinyl-coenzyme A is converted to succinate
2. succinate thiokinase
3. NDP + Pi –> NTP + CoA
4. Free energy of thioester bond is conserved by formation of high energy NTP

Question 6

What is the sixth reaction of the citric acid cycle

Answer 6

1. Succinate is converted to fumarate
2. Succinate dehydrogenase
3. Oxidation of succinate’s single bond to form a double bond.
4. FAD–>FADH2

Question 7

What is the seventh reaction of the citric acid cycle

Answer 7

1. Fumarate converted to malate
2. Fumarase
3. Fumarate’s double bond is hydrolysed- water put in

Question 8

What is the eighth reaction of the citric acid cycle

Answer 8

1. Fumarate converts to oxaloacetate
2. Malate dehydrogenase
3. Oxidises malate’s secondary alcohol to ketone
4. Reduction NAD+–>NADH + H+

Question 9

What is the overall products and reactants of the citric acid cycle

Answer 9

3 NAD+ + FAD + GDP + Pi + acetyl-CoA –> 3NADH + FADH2 + GTP + CoA + 2CO2