In the presence of oxygen, most living cells make ATP by oxidative phosphorylati

Question

In the presence of oxygen, most living cells make ATP by oxidative phosphorylation, which takes place in mitochondria. One of the major substrates that is oxidized is NADH. The overall reaction for this energy yielding process is use Table 4.1 to calculate the Gibbs free-energy change of the above reaction as it takes place in mitochondria at pH 7 and 25degreeC. The concentration of reactants and products are [NADH]=2 mM, [NAD+]=1 mM, and Po2= 0.05 atm. Given that 4 mol of ATP is made from Pi and ADP for every mole of NADH oxidized, what fraction of the Gibbs free-energy change of part a) is use in making ATP in mitochondria during oxidative phosphorylation? [ADP]= 2 mM, [ATP]= 4 mM, and Pi=7 mM.

Explanation / Answer

(a): The given reaction is

NADH + H+ + 1/2 O2 --- > NAD+ + H2O, E0(pH7) = + 0.320

DeltaG0 = - nFE0(pH7) = - 1x96500x0.320 = 30.88 KJ

DeltaG = DeltaG0 + RTxlnQ = DeltaG0 + RTxln[NAD+] / [NADH]X[H+]

= 30.88 KJ + 8.314 JK-1mol-1x 298K x ln(1x10-3M)/(2x10-3M)x10-7M

= 69.1 KJ

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