Metabolism is the chemical process that involves the extraction of chemical ener
ID: 917357 • Letter: M
Question
Metabolism is the chemical process that involves the extraction of chemical energy from sugars and fats. One such reaction is:
C6H12O6 + 6O2 6CO2 + 6H2O, Go = -2870 kJ
Some of this energy may be used to synthesize energy transport molecules, the most important of which is adenosine triphosphate (ATP).
ADP+H3PO4 ATP+H2O,Go=+30.6kJ
a) How many ATP could be synthesized from the combustion of 1.0 mol of glucose?
b) Under normal physiological conditions, only 36 ATP molecules are produced. What percent of the energy is used and what percent is wasted? Where does the waste go?
Another biochemical reaction that produces ATP involves the conversion of acetylphosphate (CH3CO2PO3H2) to acetic acid and phosphoric acid.
CH3CO2PO3H2 + H2O HC2H3O2 + H3PO4, Go = -46.9 kJ
c) Write the balanced chemical equation that shows the coupling of the acetylphosphate hydrolysis reaction and the ATP synthesis reaction. Determine the free energy change.
Explanation / Answer
Energy released from combustion of 1 mole of glucose = 2870 kJ
Energy needed to produce 1 molecule of ATP = 30.6 kJ
=> Number of ATP molecules that could be synthesized from the combustion of 1.0 mol of glucose = 2870 / 30.6 = 93.8 molecules of ATP
b)
% ATP used = 36 x 100 / 93.8 = 38.38 %
% ATP wasted = (93.8 - 36) x 100 / 93.8 = 61.62 %
c)
Given,
CH3CO2PO3H2 + H2O HC2H3O2 + H3PO4, Gº = -46.9 kJ / mol
We know that a coupling process links a spontaneous reaction with a non spontaneous one.
The energy released in acetyl phosphate reaction provides the energy needed for the conversion of ADP to ATP
We also know that
ADP + H3PO4 -----> ATP + H2O Gº = 30.6 kJ / mol
The coupled reaction is:
CH3CO2PO3H2 + H2O HC2H3O2 + H3PO4, Gº = -46.9 kJ / mol
ADP + H3PO4 -----> ATP + H2O Gº = 30.6 kJ / mol
NET REACTION: CH3CO2PO3H2 + ADP -----> HC2H3O2 + ATP
Gº coupled reaction = - 46.9 + 30.6 = - 16.3 kJ / mol