Kerbs Cycle

Question 1

During krebs cycle, each of the ___ reactions are ____ by a different ____

Answer 1

• Happens twice, one in each Acetyl CoA molecule
• 8 Reactions, each catalyzed by a different enzyme

Question 2

Krebs cycle phases

Answer 2

1. An acetyl group from acetyl CoA (2C) condenses with oxaloacetate (4C) to form citrate (6C)
2. Citrate is rearranged forming isocitrate (6C)
3. Isocitrate is converted into alpha ketoglutarate (5C) by removing CO2 and 2 H+ which reduces NAD+ into NADH
4. Alpha ketoglutarate is converted into succinyl CoA (4C). CO2 is removed, coenzyme is added and 2 H atoms reduce NAD+ into NADH
5. Succinyl CoA (4C) is converted into succinate (4C) ATP is formed by substrate level phosphorylation and coenzyme A is released
6. Succinate (4C) is converted to fumarate (4C). 2 H atoms reduce FAD to FADH2
7. Fumarate (4C) is converted to malate (4C).
8. Malate (4C) is converted into oxaloacetate (4C). 2 H atoms reduce NAD + to NADH.

REMEMBER: This cycle happens twice, once for each Acetyl-CoA

Question 3

Krebs cycle end products

Answer 3

At the end of Krebs Cycle…
• 2 ATP (1 per pyruvate)
• 4 CO, molecules (2 per pyruvate)
• 6 NADH (3 per pyruvate)
• 2 FADH, (1 per pyruvate)

Question 4

What will happen to the glucose at this point, end of Krebs cycle? (Carbon molecules and its energy)

Answer 4

• By the end of Krebs Cycle (stage 3), all 6 carbons in the original glucose molecule have been oxidized to CO, and released as waste

• All that is left of the original glucose is free energy in the form of ATP, FADH, and NADH

Question 5

End product of stages 1-3

Answer 5

From the beginning of glycolysis, to the end of Krebs cycle, 1 glucose will produce:
• 4 ATP
• 6 CO2
• 10 NADH
• 2 FADH2