In a calorimeter, the combustion of 1 mole of glucose produces 690 kcal. a.What
ID: 1035982 • Letter: I
Question
In a calorimeter, the combustion of 1 mole of glucose produces 690 kcal.
a.What percentage of ATP energy is produced when 7 moles of glucose react in glycolysis? (7.3 kcal/mole ATP)
b.What percentage of ATP energy is produced when 7 moles of glucose are oxidized into acetyl CoA? (7.3 kcal/mole ATP)
c.What percentage of ATP energy is produced when 7 moles of glucose react in the citric acid cycle? (7.3 kcal/mole ATP)
d.What percentage of ATP energy is produced when 7 moles of glucose are completely oxidized to CO2 and H2O? (7.3 kcal/mole ATP)
Explanation / Answer
Ans. Given, energy released from combustion of glucose = 690 kcal/mol
So,
Total energy released from combustion of 7 mol glucose =
Molar enthalpy of combustion x Moles of glucose
= (-690 kcal/mol) x 7 mol
= -4830.0 kcal
Note: The –ve sign indicates release of energy.
#a. Total ATP produced in glycolysis = ATP per glucose in glycolysis x Mol of Glu
= (2 ATP/ glucose) x 7 ATP
= 14 ATP
# Total energy conserved in ATP = No. of ATP x dG0’ of ATP hydrolysis
= 14 ATP x (-7.3 kcal mol-1 ATP-1)
= -102.2 kcal
Now,
% energy conserved in ATP =
(Energy conserved in ATP / Total energy released from glucose) x 100
= [-102.2 kcal / (-4830 kcal)] x 100
= 2.12 %
#b. Glycolysis yields 2 pyruvates + 2 ATP from 1 glucose. Each pyruvate is oxidized to acetyl-CoA by pyruvate dehydrogenase complex without any ATP production.
SO, oxidation of glucose to acetyl-CoA produces 2 ATP per glucose.
So, Total ATP produced till acetyl-CoA formation =
ATP per glucose till acetyl-CoA formation x Mol of Glu
= (2 ATP/ glucose) x 7 ATP
= 14 ATP
# Total energy conserved in ATP = No. of ATP x dG0’ of ATP hydrolysis
= 14 ATP x (-7.3 kcal mol-1 ATP-1)
= -102.2 kcal
Now,
% energy conserved in ATP =
(Energy conserved in ATP / Total energy released from glucose) x 100
= [-102.2 kcal / (-4830 kcal)] x 100
= 2.12 %
#c. Note: ATP produced only during TCA (1 substrate level phosphorylation per pyruvate. Thus, 2 ATP per glucose) is accounted.
Total ATP produced in TCA = ATP per glucose in TCA x Mol of Glu
= (2 ATP/ glucose) x 7 ATP
= 14 ATP
# Total energy conserved in ATP = No. of ATP x dG0’ of ATP hydrolysis
= 14 ATP x (-7.3 kcal mol-1 ATP-1)
= -102.2 kcal
Now,
% energy conserved in ATP =
(Energy conserved in ATP / Total energy released from glucose) x 100
= [-102.2 kcal / (-4830 kcal)] x 100
= 2.12 %
#d. Complete oxidation of glucose includes the following processes-
Glycolysis ----Glycolysis------> 2 Pyruvate + 2 ATP + 2 NADH
2 Pyruvate ----PDH-------------> Acetyl-CoA + 2 NADH
2 Acetyl-CoA ---------TCA-----> 2 CO2 + 2 ATP + 6 NADH + 2FADH2
10 NADH + 2FADH2 -----ETC--> 28 ATP + H2O
That is, complete oxidation of 1 glucose produces 32 ATP/ glucose.
# Total ATP produced upon complete oxidation = ATP per glucose x Mol of Glu
= (32 ATP/ glucose) x 7 ATP
= 224 ATP
# Total energy conserved in ATP = No. of ATP x dG0’ of ATP hydrolysis
= 224 ATP x (-7.3 kcal mol-1 ATP-1)
= -1635.2 kcal
Now,
% energy conserved in ATP =
(Energy conserved in ATP / Total energy released from glucose) x 100
= [-1635.2 kcal / (-4830 kcal)] x 100
= 33.86 %