# Muscle cells need energy to contract. One biochemical pathway for energy transfer is the breakdown of glucose to pyruvate in a process called glycolysis . In the presence of sufficient oxygen in the cell, pyruvate is oxidized to CO 2 and H 2 O to make further energy available. However, under extreme conditions not enough oxygen can be supplied to the cells, so muscle cells produce lactate ion according to the reaction where Δ r G °′ = −25.1 kJ/mol. In living cells, the pH value is about 7. The hydronium ion concentration is constant and is included in Δ G °, which is then called Δ r G °′ ( Applying Chemical Principles 18.1 Thermodynamics and Living Things ). ( This problem is taken from the problems for the 36th International Chemistry Olympiad for high school students held in Kiel Germany in 2004 .) (a) Calculate Δ r G ° for the reaction at 25 °C. (b) Calculate the equilibrium constant K ′ . (The hydronium ion concentration is included in the constant. That is, K′ = K · [H 2 O + | for the reaction at 25 °C and pH = 7.0.) (c) Δ r G ° is the free energy change under standard conditions; that is, the concentrations of all reactants (except H 3 O + are 1.00 mol/L. Calculate Δ r G ° at 25 °C, assuming the following concentrations in the cell: pyruvate, 380 μ mol/L; NADH, 50 μ mol/L; lactate ion, 3700 μ mol/L; and NAD + ion, 540 μ mol/L.

### Chemistry & Chemical Reactivity

10th Edition
John C. Kotz + 3 others
Publisher: Cengage Learning
ISBN: 9781337399074

### Chemistry & Chemical Reactivity

10th Edition
John C. Kotz + 3 others
Publisher: Cengage Learning
ISBN: 9781337399074

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Chapter 18, Problem 106SCQ
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