Q.Why is less energy produced during anaerobic respiration than in aerobic respiration?

Step 1. Compare how far glucose is broken down in each case. In anaerobic respiration, glucose is broken down only as far as glycolysis (to pyruvic acid) and then partially converted to lactic acid or ethanol - most of the chemical bond energy originally present in glucose remains locked inside these still-organic end products, unreleased.

Step 2. Compare how far glucose is broken down in aerobic respiration. In aerobic respiration, the same pyruvic acid is instead completely oxidised - through the link reaction, the Krebs cycle, and the electron transport chain - all the way down to CO2 and water, extracting essentially all the energy originally stored in the glucose molecule. …

Comparing how completely glucose is oxidised in each pathway, and tracing that difference thro …

• Vaguely saying 'because oxygen is not used', without explaining WHY that specifically limits ATP yield - the real reason is that oxidative phosphorylation (which needs oxygen as the final electron acceptor) accounts for the great majority of aerobic ATP production. …