In which of the following reactions of respiration oxygen is required?

Correct option is B

The process that requires oxygen in respiration is the conversion of pyruvate to CO₂, H₂O, and energy. This occurs in the aerobic respiration pathway, specifically during the Krebs cycle and electron transport chain. Oxygen is the final electron acceptor in the electron transport chain, which helps produce large amounts of ATP (energy) by completing the breakdown of pyruvate into carbon dioxide and water.

Important Key Points:

1. Aerobic respiration requires oxygen to fully oxidize glucose, producing CO₂, H₂O, and energy.
2. The conversion of pyruvate to CO₂ and H₂O takes place in the mitochondria.
3. Oxygen plays a critical role in the electron transport chain to generate ATP.
4. Without oxygen, cells resort to anaerobic respiration, producing less energy and by-products like lactic acid or ethanol.
5. The conversion of glucose to pyruvate (glycolysis) and the conversion of pyruvate to ethanol (fermentation) do not require oxygen.

Information Booster:

• Anaerobic conditions (Option c) result in fermentation (ethanol or lactic acid formation), which does not require oxygen but produces less energy.
• Conversion of pyruvate to ethanol (Option c) occurs in yeast and some bacteria under anaerobic conditions, where oxygen is not used.
• Krebs cycle and electron transport chain (Option b) are parts of aerobic respiration, where oxygen is essential for energy production.