Question

In the electron transport chain, the oxidation of NADH to NAD+ is coupled to the reduction of O2 in to H2O, and 3.5 ATP molecules are made from ADP and Pi, for each molecule of NADH. Remember to show all work!

i) Write out the balanced REDOX reaction involving NADH and O2 as substrates.

ii) Calculate the ΔE°’ and ΔG°’ for the reaction, where one mole of NADH molecules is oxidized.

iii) How much energy is required to make 3.5 mol of ATP molecules from ADP and Pi ?

iv) What percentage of the energy associated with NADH oxidation is stored as ATP?

Answer 1

(i). The balanced REDOX reaction involving NADH and O2 as substrates is given as:

NADH   +    H+     + 1/2 O2        NAD+     +      H2O

(ii). For the above reaction:

Eo = 1.14 V

We know that:

Go = - nFEo

= - 1 * 96485 * 1.14

= - 109992.9 J

Go = - 109.99 kJ

(iii). For the formation of 1 mole of ATP molecules, energy required = 30.5 kJ

ADP    +    Pi           ATP    +     H2O    ................ Go = 30.5 kJ/mol

Energy required to make 3.5 mol of ATP molecules = 3.5 * 30.5

= 106.75 kJ