Question

In aerobic respiration, the final electron acceptor is

• A. Carbon dioxide
• B. Oxygen
• C. Nitrate
• D. Sulphate

Hint:

Remember the sequence of aerobic respiration: \[ \boxed{\text{Glucose} \rightarrow \text{Glycolysis} \rightarrow \text{Krebs Cycle} \rightarrow \text{ETC} \rightarrow O_{2}} \] Oxygen is the final electron acceptor and combines with electrons and hydrogen ions to form water, allowing maximum ATP production.

Answer 1

The Correct Option is B

Concept: Aerobic respiration is the process by which cells produce energy (ATP) in the presence of oxygen. During this process, electrons released from glucose are transferred through the Electron Transport Chain (ETC). At the end of the chain, oxygen accepts these electrons and combines with hydrogen ions to form water.
• Aerobic respiration occurs mainly in the mitochondria.
• Oxygen acts as the terminal (final) electron acceptor.
• Acceptance of electrons by oxygen allows the ETC to continue functioning.
• This process produces the maximum amount of ATP.

Step 1: Understand the Electron Transport Chain (ETC).
During cellular respiration: \[ \text{Glucose} \rightarrow \text{Glycolysis} \rightarrow \text{Krebs Cycle} \rightarrow \text{Electron Transport Chain} \] Electrons are transferred through a series of protein complexes until they reach oxygen.

Step 2: Role of oxygen.
At the end of the ETC, \[ O_{2}+4e^{-}+4H^{+} \longrightarrow 2H_{2}O \] Thus, oxygen combines with electrons and hydrogen ions to form water. Without oxygen:
• Electron flow stops.
• ATP production decreases drastically.
• Cells switch to anaerobic respiration (if possible).

Step 3: Eliminate the incorrect options.

• Carbon dioxide is a waste product of respiration, not an electron acceptor.
• Nitrate and sulphate act as terminal electron acceptors only in certain anaerobic microorganisms.
• Oxygen is the terminal electron acceptor in aerobic respiration. Therefore, \[ \boxed{Option (B) is the correct answer. \]