An important reaction in the production of energy from sugars (glycolysis) is the reduction of pyruvate to lactate by NADH. pyruvate + NADH + H⁺(aq) → lactate + NAD⁺ Δ_rG°′ = ?
Given the following reduction potentials,
NAD⁺ + H⁺ + 2e− → NADH
Ε°′ = −0.320 V
Pyruvate + 2H⁺ + 2e⁻ → lactate
Ε°′ = −0.190 V
Calculate the standard Gibbs free energy (at pH 7) for the reduction of pyruvate to lactate by NADH.(Δ_rG°′ = −nFE°′; F = 96485 C/mol electrons)

Question

Quizplus · Accepted Answer

Using the given reduction potentials, we can calculate the overall standard cell potential (ΔE°′) for the reaction: NADH + pyruvate → lactate + NAD+ ΔE°′ = ΔE°′(lactate) - ΔE°′(pyruvate) - ΔE°′(NAD+) + ΔE°′(NADH) ΔE°′ = (0 V - (-0.190 V) - (-0.000 V) + (-0.320 V)) = 0.130 V Using Δ_rG°′ = -nFE°′ and substituting the values, we get: Δ_rG°′ = -(-2 mol) x (96485 C/mol e-) x (0.130 V) = 25.1 kJ/mol-rxn Therefore, the standard Gibbs free energy for the reduction of pyruvate to lactate by NADH is -25.1 kJ/mol-rxn (negative sign indicates a spontaneous reaction).

An Important Reaction in the Production of Energy from Sugars