ATP is the source of energy for most biological processes. ATP delivers energy through thermodynamic coupling during biological reactions. Alanine + Glycine ⟶ Alanylglycine; Δ G = + 29 k J m o l − 1 A

Question

ATP is the source of energy for most biological processes. ATP delivers energy through thermodynamic coupling during biological reactions.

Alanine + Glycine $⟶$ Alanylglycine; $Δ G = + 29 k J m o l^{- 1}$

ADP + H₃PO₄ $⟶$ ATP; $Δ G = + 31 k J m o l^{- 1}$

The nitrite ion in soil is oxidized to nitrate ion by the bacteria *Nitrobacter agilis* in the presence of oxygen. The half-reduction reactions are:

$N O_{3}^{-} + 2 H^{+} + 2 e^{-} ⟶ N O_{2}^{-} + H_{2} O; E^{\circ} = + 0.42 V$

$O_{2} + 4 H^{+} + 4 e^{-} ⟶ 2 H_{2} O; E^{\circ} = + 1.23 V$

Calculate the yield of ATP synthesis (in terms of number of moles of ATP) per mole of nitrite oxidized.

TestHub · Accepted Answer

The standard free-energy change, Δ G 0 , can be calculated from the cell potential: E cell 0 ​ = E cathode 0 ​ − E anode 0 ​ = 1.23 V − 0.42 V = 0.81 V Δ G 0 Δ G 0 Δ G 0 ​ = − nFE cell 0 ​ = − ( 4 ) ( 96 , 500 J / V ⋅ mol ) ( 0.81 V ) = − 3.13 × 1 0 5 J / mol = − 313 kJ / mol ​ This is the free-energy change for the oxidation of 2 moles of nitrite ( NO 2 − ​ ). It takes 31 kJ of free energy to synthesize 1 mole of ATP from ADP. The yield of ATP synthesis per mole of nitrite oxidized is:

Chemistry - Thermodynamics - II Question with Solution | TestHub

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