4. Using the standard Gibbs free energy of reaction reported in Table 14-2 of Le

Question

4. Using the standard Gibbs free energy of reaction reported in Table 14-2 of Lehninger to determine the standard Gibbs free energy of glycolysis: glucose + NAD" + 2 ADP + 2 Pi 2 pyruvate + 2 NADH + 2 ATP + 2 H2O 5. Select a "high energy" substrate (not PEP) for hydrolysis that can be used to drive ATP synthesis. Write down the hydrolysis reaction and the standard Gibbs free energy for the reaction. Write down the coupled reaction and calculate the standard Gibbs free energy for the coupled reaction. 6. Glucose comprises 6 carbon atoms. Indicate the oxidation state of each carbon in glucose. Glycolysis produces pyruvate. Indicate the oxidation state of each carbon in pyruvate. What is the net change in carbon oxidation states during glycolysis? How does lactic acid fermentation affect the net change in carbon oxidation states going from glucose to lactate?

Explanation / Answer

In a combined reaction, G reaction is the summation of free-energy changes of its individual components, therefore, coupled reaction (endergonic and exergonic) is energetically favorable and will proceed. Thus, the energetically unfavorable reaction which require energy that is endergonic are coupled with exergonic reactions. Enzymes play an important role in this for carrying out such coupled reactions in a synchronized manner.

For the present reaction

Total exergonic=-81.1kJ/mol

Total endergonic=+51.2

Therefore, net standard Gibbs free energy= - 29.9kJ/mol

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