Question

The ratio that approximates, the number of net molecules of ATP formed per mole of glucose oxidised in the presence of oxygen to net number formed in its absence is

• A. 4:1
• B. 10:1
• C. 18:1
• D. 24:1

Hint:

ATP Yield Comparison: Aerobic (36 ATP) vs Anaerobic (2 ATP) $\implies$ Ratio is $36:2 = 18:1$. Demonstrates the Pasteur Effect.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Comparative energetic efficiency of complete aerobic cellular respiration vs anaerobic substrate-level glycolysis.
Key Formula or Approach:
\[ \text{Ratio} = \frac{\text{Aerobic ATP Yield}}{\text{Anaerobic ATP Yield}} = \frac{36\text{ (or 38) ATP}}{2\text{ ATP}} = 18:1 \]

Step 2: Detailed Explanation:
Calculating net ATP yields per mole of glucose:
1. Aerobic Complete Oxidation: Glycolysis ($+2\text{ ATP} + 2\text{ NADH}$) $+$ Pyruvate Decarboxylation ($+2\text{ NADH}$) $+$ TCA Cycle ($+2\text{ GTP} + 6\text{ NADH} + 2\text{ FADH}_2$) followed by oxidative phosphorylation yields a net of 36 to 38 ATP (or $30-32\text{ ATP}$ by modern P/O ratios).
2. Anaerobic Glycolysis: Yields a net of only 2 ATP via substrate-level phosphorylation (NADH is re-oxidized to lactate without generating ATP).
3. Ratio: $\frac{36}{2} = 18:1$.

Step 3: Final Answer:
Therefore, the ratio is 18:1, corresponding to option (C).