TCA Cycle

Question 1

Step 1, reactants, products, enzyme, if irreversible or ATP required/released.

Answer 1

• Acetyl-CoA + oxaloacetate -> citrate + CoA-SH

- Citrate synthase, uses H2O

Question 2

Step 2, reactants, products, enzyme, if irreversible or ATP required/released.

Answer 2

• Citrate -> cis-aconitate -> isocitrate

- Aconitase, uses H2O (2 total)

Question 3

Step 3, reactants, products, enzyme, if irreversible or ATP required/released.

Answer 3

• Isocitrate -> α-ketogluterate + CO2
• Isocitrate dehydrogenase
• NAD+ -> NADH + H+

Question 4

Step 4, reactants, products, enzyme, if irreversible or ATP required/released.

Answer 4

α-ketogluterate -> succinyl-CoA + CO2
-α-ketogluterate dehydrogenase
-Requires CoA-SH (step 1/5)
NAD+ -> NADH + H+

Question 5

Step 5, reactants, products, enzyme, if irreversible or ATP required/released.

Answer 5

• Succinyl-CoA -> Succinate
• Succinyl-CoA synthase
• GDP -> GTP
• Releases CoA-SH

Question 6

Step 6, reactants, products, enzyme, if irreversible or ATP required/released.

Answer 6

• Succinate -> fumerate
• Succinate dehydrogenase
• FAD -> FADH2

Question 7

Step 7, reactants, products, enzyme, if irreversible or ATP required/released.

Answer 7

• Fumerate -> L-malate

- Fumerase

Question 8

Step 8, reactants, products, enzyme, if irreversible or ATP required/released.

Answer 8

• L-malate -> oxaloacetate
• Malate dehydrogenase
• NAD+ -> NADH + H+

Question 9

Steps releasing CoA-SH

Answer 9

1 and 5.

Question 10

Steps releasing FADH2

Answer 10

6.

Question 11

Steps releasing NADH

Answer 11

3, 4, and 8.

Question 12

Before step 1

Answer 12

• Pyruvate + CoA -> acetyl-CoA
• Pyruvate dehydrogenase
• Produces CO2 and NADH