Question

You have a critical biochemical reaction that needs to occur in cells to allow glucose metabolism. the change in gibbs free energy is 12.3 kj/mol. which of the following reactions would be appropriate to couple this reaction to ensure metabolism occurs?

a) 20 kJ/mol
b) 10 kJ/mol
c) -20 kJ/mol
d) -10 kJ/mol

Answer 1

To ensure glucose metabolism occurs, the reaction with a ΔG of 12.3 kJ/mol should be coupled with a reaction that releases more energy, specifically the -20 kJ/mol reaction, making it energetically favorable and spontaneous.

Step-by-step explanation:

The question you are asking pertains to the coupling of biochemical reactions to ensure that a reaction with a positive change in Gibbs free energy (ΔG) proceeds. The reaction in question requires 12.3 kJ/mol for glucose metabolism to occur. To drive this non-spontaneous reaction forward, it needs to be coupled with a spontaneous (exergonic) reaction that releases more energy than is consumed by the endergonic reaction.

The correct answer to which reaction should be coupled is c) -20 kJ/mol. This is because the reaction with ΔG of -20 kJ/mol releases more free energy than is required for the glucose metabolism reaction, making the overall coupled reaction exergonic and therefore spontaneous under standard conditions.

In summary, reactions with negative ΔG release energy and can be used to power reactions that consume energy, such as the one required for glucose metabolism. Therefore, by coupling the 12.3 kJ/mol endergonic reaction with a -20 kJ/mol exergonic reaction, the overall process becomes energetically favorable.