Net ATP Yield in Fermentation — NEET Biology
✅ Asked in NEET 2022In both lactic acid and alcohol fermentation not much energy is released; less than seven per cent of the energy in glucose is released and not all of it is trapped as high energy bonds of ATP. Also, the processes are hazardous – either acid or alcohol is produced. What is the net ATPs that is synthesised (calculate how many ATP are synthesised and deduct the number of ATP utilised during glycolysis) when one molecule of glucose is fermented to alcohol or lactic acid? Yeasts poison themselves to death when the concentration of alcohol reaches about 13 per cent. What then would be the maximum concentration of alcohol in beverages that are naturally fermented? How do you think alcoholic beverages of alcohol content greater than this concentration are obtained?
NTA tests students on calculating net ATP produced during fermentation by subtracting ATP consumed (2 ATP in glycolysis) from ATP generated (2 ATP in glycolysis). The key trap is that fermentation does NOT produce additional ATP beyond glycolysis—the fermentation step (lactate or ethanol formation) only regenerates NAD+ to keep glycolysis running. Students mistakenly think fermentation produces extra ATP. Remember: Net ATP from one glucose = 2 ATP (only from glycolysis), because fermentation has zero net ATP synthesis. This explains why less than 7% of glucose's energy is captured compared to aerobic respiration's ~38 ATP, making fermentation energetically poor but essential for anaerobic survival.
What amount of energy is released from glucose during lactic acid fermentation? (NEET 2022 Phase 1)
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