Question

The number of ATP produced when one molecule of pyruvic acid is used as respiratory substrate in Kreb's cycle?

• A. $15$
• B. $12$
• C. $3$
• D. $36$

Answer 1

The correct option is A $15$

When one molecule of pyruvic acid is used as respiratory substrate in Kreb's cycle, 15 ATP molecules are produced. In Kreb's cycle, 1 molecule of FADH2 and 4 molecules of NADH are produced. One molecule of FADH2 produces 2 ATP molecules in ETS. Four molecules of NADH produces 4 x 3 = 12 molecules of ATP. Also, 1 molecule of ATP is produced by substrate level phosphorylation. Hence, total number of ATP molecules produced by 1 molecule of pyruvic acid during Krebs cycle = 12+2+1 = 15.

Thus, the correct answer is '15.'