How many ATP molecules are produced by Cellular respiration

Solution

The theoretical yield of ATP is 36 to 38 ATP per glucose. While the actual yield is, 30 to 32 ATP. This is because, during the calculation of theoretical yield, the energy necessary for the transport of ATP into the cytoplasm and out of the mitochondria is not considered. Only the ATPsynthesized by oxidative phosphorylation inside the mitochondria is considered.

In case of actual yields, the energy needed for the transport of ATP is also considered. In this, 2 ATP molecules are derived from the glycolysis and the remaining 26 or 30 from the oxidative phosphorylation.

The theoretical and actual yield of ATP in Aerobic Respiration:

Phases of Respiration

ATP made directly

Reduced coenzymes

Theoretical yield from oxidative phosphorylation

Actual yield from oxidative phosphorylation

Glucose to pyruvate (in cytoplasm)

2 ATP (net gain)

2 NADH that goes into mitochondria as 2 FADH₂

From FADH₂:

2 ATP (× 2) = 4 ATP

Or from NADH:

3 ATP (× 2) = 6 ATP

From FADH₂:

1.5 ATP (× 2) = 3 ATP

Or from NADH:

2.5 ATP (× 2) = 5 ATP

Pyruvate to acetyl CoA (× 2)

None

1 NADH (× 2) = 2 NADH

3 ATP (× 2) = 6 ATP

2.5 ATP (× 2) = 5 ATP

Citric acid cycle (× 2)

1 ATP (× 2) = 2 ATP

3 NADH (× 2) = 6 NADH

1 FADH₂ (× 2) = 2 FADH₂

3 ATP (× 6) = 18 ATP

2 ATP (× 2) = 4 ATP

2.5 ATP (× 6) = 15 ATP

1.5 ATP (× 2) = 3 ATP

Total ATP

4 ATP

32 or 34 ATP

26 or 28 ATP

Fermentation is a process of anaerobic catabolism. It is the continuation of glycolysis in the absence of oxygen. However, this process needs the supply of NAD+ as an electron acceptor. NAD+ is produced in aerobic conditions, fermentation occurs as long as NAD+ reserves are available.

During fermentation, pyruvate is metabolized to lactic acid and produces 2 molecules of ATP. The lactic acid produced during this process can again be converted into glucose in the liver.