[Campbell Biology P.214] According to the text, what is the approximate free-energy change w... | Practice Question

According to the text, what is the approximate free-energy change when one mole of glucose is decomposed, and what does a negative value for this change indicate?

  • A: -686 kcal (-2,870 kJ); it indicates that the products store less energy than the reactants and the reaction is spontaneous.
  • B: +686 kcal (+2,870 kJ); it indicates that the products store more energy than the reactants and the reaction requires energy input.
  • C: -686 kJ (-2,870 kcal); it indicates that the reaction is non-spontaneous and requires ATP.
  • D: The exact value varies greatly depending on cell conditions, but a negative value always means energy is absorbed.

Explanation

The text states that the breakdown of glucose is exergonic, 'having a free-energy change of -686 kcal –2,870 kJ per mole of glucose decomposed.' It further explains that 'a negative ΔG ΔG < 0 indicates that the products of the chemical process store less energy than the reactants and that the reaction can happen spontaneously.' This aligns perfectly with option A.