Question

In a calorimeter, the combustion of 1 mole of glucose produces 690 kcal.

1. What percentage of ATP energy is produced when 3 moles of glucose react in glycolysis? (7.3 kcal/mole ATP)

2. What percentage of ATP energy is produced when 3 moles of glucose are oxidized into acetyl CoA? (7.3 kcal/mole ATP)

3. What percentage of ATP energy is produced when 3 moles of glucose react in the citric acid cycle? (7.3 kcal/mole ATP)

4. What percentage of ATP energy is produced when 3 moles of glucose are completely oxidized to CO2 and H2O? (7.3 kcal/mole ATP)

Answer 1

1 mole of glucose (C₆H₁₂O₆) produces 690 kcal of energy upon combustion.

1. During glycolysis, 1 mole of glucose produces 2 moles of ATP and 2 moles of NADH.

Therefore, a total of 7 moles of ATP is produced. For, 3 moles of glucose, 21 moles of ATP will be produced.

So,

  

  

2. For the formation of acetyl Co-A, 1 mole of pyruvate along with 1 mole of NAD⁺ produces 1 mole of Acetyl Co-A, 1 mole of NADH and 1 mole of CO₂ is released.

i.e. 2.5 moles of ATP are produced per pyruvate molecule. Therefore, a total of 5 moles of ATP is produced from 1 mole of glucose.

So,

  

3. From one Krebs cycle or citric acid cycle, 3 moles of NADH, 1 mole of FADH₂ and 1 mole of GTP are produced.

Now,

i.e. 10 moles of ATP are produced per Acetyl Co-A molecule. Therefore, a total of 20 moles of ATP is produced from 1 mole of glucose.

So,

4. The overall reaction for the complete combustion of glucose (1 mole) is

C6H12O6+6O2→6CO2+6 H2O+30/32 ATP

This variable ATP production is due to oxidative phosphorylation where each NADH produces net 1.5 ATP (instead of usual 2.5) due to NADH transport over the mitochondrial membrane. So somewhere, 1 mole of glucose produces 30 moles of ATP and in other places, it produces 32 moles of ATP.