Biology · Respiration in Plants · NEET
No. Oxygen does NOT make ATP by itself. Oxygen only accepts the electrons at the end of the chain and forms water. This keeps the electron transport system running. The actual ATP is made by the enzyme ATP synthase (Complex V) using the proton gradient. So oxygen's job is to keep the chain 'open', not to build ATP directly. NEET often confuses students here.
Oxygen acts only at the last step of the ETS, on the inner mitochondrial membrane. Electrons first pass through Complex I to IV (the cytochromes). Only after this final stage does oxygen accept the electrons. NCERT clearly says oxygen acts at the 'terminal stage' — it is not involved in glycolysis or the Krebs cycle.
Water (H2O) is formed. Oxygen takes the electrons and combines with protons (H+ ions). The reaction can be written as: O2 + 4H+ + 4e- gives 2H2O. This is why oxygen is called the final electron and hydrogen acceptor. Water is the safe end product that removes the electrons from the chain.
If oxygen is absent, there is nothing to accept the electrons at the end. The electrons then get 'stuck' and the whole chain backs up — NADH cannot be re-oxidised to NAD+. Without NAD+, the Krebs cycle and ETS stop. This is why aerobic respiration needs oxygen: it removes electrons so the chain can keep flowing and ATP can keep forming.
Oxygen is the final electron ACCEPTOR, not the final product. The final product formed is water. Remember: oxygen is the receiver, water is the result. NEET may word an option as 'oxygen is the final product' — that is wrong. The correct statement is 'oxygen is the final electron acceptor and water is formed'.
Try the real previous-year questions from this chapter — each with the answer and a full solution.
Oxygen is the final (terminal) electron acceptor. It receives electrons at the end of the chain and combines with protons to form water, allowing the chain to keep running.
Because it acts at the very last step of the electron transport system, after Complexes I to IV. No electron carrier comes after oxygen, so it is 'terminal' or final.
Oxygen accepts the electrons and combines with H+ ions to form water (H2O). This is the metabolic water produced during aerobic respiration.
No. Without oxygen the electrons have nowhere to go, the chain backs up, NAD+ is not regenerated, and aerobic ATP production stops. This is why aerobic respiration is oxygen-dependent.
No. Oxygen is not directly used in glycolysis or the Krebs cycle. It acts only at the terminal stage of the ETS. This is an important NEET point.
