Question

The $\Delta G^\circ$ for homolactic fermentation converting glucose to lactate is –196 kJ mol$^{-1}$. If $\Delta G^\circ$ for the formation of ATP is +30.5 kJ mol$^{-1}$, then

• A. homolactic fermentation is 31% energy efficient
• B. the efficiency of energy conservation is 69%
• C. the energy stored in the form of ATP is 31%
• D. the process results in the loss of 31% of energy

Hint:

Always multiply by the number of ATP formed per glucose when calculating efficiency.

Answer 1

The Correct Option is A, C

Step 1: Calculate energy conserved as ATP.
ATP formation requires 30.5 kJ/mol. Homolactic fermentation releases 196 kJ/mol.
Step 2: Compute percentage stored as ATP.
Energy stored fraction = $\dfrac{30.5}{196} \approx 0.155$. But two ATP are formed → $\dfrac{2 \times 30.5}{196} = \dfrac{61}{196} \approx 0.31 = 31%$.
Step 3: Conclusion.
Thus, 31% of the energy is stored as ATP.