Question

How many ATP are produced in cellular respiration?

Answer 1

Aerobic cellular respiration produces a total of 36 or 38 ATPs, as described below.

Process	ATPs	Produced by
Glycolysis	2	Substrate level phosphorylation
Glycolysis	6 or 4	Oxidative phosphorylation of 2 NADH2
Link Reaction	6	Oxidative phosphorylation of 2 NADH2
Krebs' Cycle	2	Substrate level phosphorylation
	4	Oxidative phosphorylation of 2 FADH2
	18	Oxidative phosphorylation of 6 NADH

The total number of ATPs varies from 38 to 36 depending upon the shuttle system, used for transporting electrons obtained from glycolysis to mitochondria. If malate-aspartate shuttle is used (which exchanges cytoplasmic NADH with mitochondrial NADH) then 38 ATPs are produced as a NADH gives 3 ATPs after oxidative phosphorylation. If glycerol phosphate shuttle is used (which exchanges cytoplasmic NADH₂ with mitochondrial FADH₂​) then 36 ATPs are produced as a FADH₂ gives 2 ATPs by oxidative phosphorylation.