Question: 118: What amount of energy is released from glucose during lactic acid fermentation?
(1) About 10 \%
(2) Less than 7 \%
(3) Approximately 15 \%
(4) More than 18 \%
Answer: Option (2)
Explanation:
Lactic acid fermentation is an anaerobic process in which glucose is partially oxidized to lactic acid.
During this process, only glycolysis occurs, and no further oxidation of pyruvate takes place.
Glycolysis yields a net gain of 2 ATP molecules per glucose molecule.
The total energy content of one glucose molecule is approximately 686 kcal.
Energy conserved in ATP during lactic acid fermentation is about 2 \times 7.3 = 14.6 kcal.
The percentage of energy released and conserved as ATP is therefore
\frac{14.6}{686} \times 100 \approx 2 \%, which is less than 7 \%.
Hence, the correct answer is Option (2).