Question

How many ATP are produced during cellular respiration during- Glycolysis, Oxidative decarboxylation and Kreb's cycle? What is the net production of ATP? Define Respiratory Quotient.

Answer 1

Complete aerobic breakdown of one molecule of hexose result in the release of ATP molecule. 

(i) Glycolysis: Two molecules of NADPH are released during glycolysis. The glycolysis also yields 4 ATP molecules out of which 2 ATP molecules are consumed. 

Thus the glycolysis contributes a total of 2 ATP molecule. 

(ii) 2 molecules of NADH produced in glycolysis also 6 ATR so the net gain of ATP is 6 ATP. 

(iii) Oxidative decarboxylation: Two molecules of NADH are released during the oxidative decarboxylation and synthesis of acetyl Co A from pyruvic acid. Thus number of ATP molecules will be 2 x 3 = 6. 

(iv) Kreb's cycle: Kreb's cycle releases 6 molecules of NADH and 2 molecules of FADH₂. The Kreb cycle also releases 2 ATP molecules, thus total number of ATP molecules produced during Kreb's cycle are 2 + 2 × 2 + 6 × 3 = 24 molecules. 

(v) Respiratory Quotient: Respiratory quotient is the ratio of the volume of carbon dioxide produced to the volume of oxygen consumed in respiration over a period of time. Its value can be one, zero, more than one and less than one.