Pyruvate dehydrogenase complex PDC converts pyruvate to acet

Pyruvate dehydrogenase complex (PDC) converts pyruvate to acetyl-coenzyme A (CoA), which is one of the two essential substrates needed to produce citrate. A deficiency in this enzymatic complex limits the production of citrate. Because citrate is the first substrate in the citric acid cycle, the cycle cannot proceed. Alternate metabolic pathways are stimulated in an attempt to produce acetyl-CoA. What foods can be used to bypass the PDC and generate acetyl-CoA to generate ATP? How efficient is this pathway compared to the energy produced from one molecule of glucose by aerobic respiration?

Solution

The fatty foods are going to used to bypass \"Swanson conversion\" process in which there will be no activity of pyruvate dehydrogenase complex (PDC) so that there will be no generation of pyruvate. So that, acetyl co-A will be generated from beta-oxidation of fatty acids (from fatty foods) that will enter into \"citric acid\" cycle for aerobic respiration. The amount of ATP yield is very much high with oxidation of fats compared to the energy efficiency attained from aerobic respiration of glucose\"

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

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