Question

How many ATP molecules can be produced by one molecule of Acetyl coenzyme A, one molecule of PEP and one molecule of Pyruvic acid when they enter into respiratory cycle?

• A. 15, 16, 12
• B. 12, 16, 15
• C. 12, 15, 16
• D. 16, 15, 12

Hint:

Using the classical ATP count: \[ \boxed{ \begin{aligned} &\text{Acetyl-CoA} &&=12\ \text{ATP} &\text{PEP} &&=15\ \text{ATP} &\text{Pyruvate} &&=16\ \text{ATP} \end{aligned} } \]

Answer 1

The Correct Option is C

Step 1: ATP from Acetyl-CoA. One molecule of Acetyl-CoA entering the Krebs cycle produces \[ \boxed{12\ \text{ATP}} \] (using the classical ATP calculation followed in NCERT-based examinations).

Step 2: ATP from PEP. PEP first produces one ATP during its conversion to pyruvate and then pyruvate enters respiration. Hence, \[ 1+2+12=15\ \text{ATP}. \] Therefore, \[ \boxed{\text{PEP }=15\ \text{ATP}.} \]

Step 3: ATP from Pyruvic acid. Pyruvate is converted to Acetyl-CoA producing \[ 1\ \mathrm{NADH}=3\ \text{ATP}, \] followed by \[ 12\ \text{ATP} \] from the Krebs cycle. Thus, \[ 3+1+12=16\ \text{ATP}. \] Hence, \[ \boxed{\text{Pyruvic acid }=16\ \text{ATP}.} \] Therefore, the sequence is \[ \boxed{12,\;15,\;16.} \] Hence, the correct option is \[ \boxed{(C).} \]