Food Chemistry and Fish in Nutrition

6.3.2.2. Respiratory chain in the inner mitochondrial membrane

6.3.2.2. Respiratory chain in the inner mitochondrial membrane and ATP production

Pyruvate           ADP+Pi→ATP ADP+Pi→ATP                            ADP+Pi→ATP

Isocitrate                         ↑            ↑                                                            ↑

a-ketoglutarate → NAD → FMN → Co Q→Cytb→CytC₁→ CytC→ Cyta→ Cyta₃

Malate

During passage along the chain, reducing equivalents from each NADH generate three high- energy phosphate bonds by the esterification of ADP to ATP in the process of oxidative phosphorylation. However, FADH2 produces only two high- energy phosphate bonds because it transfers its reducing power to Co Q, by passing the first site for oxidative phosphorylation in the respiratory chain. A further high-energy phosphate is generated at the level of the cycle itself (i.e., at substrate level) during the conversion of succinyl -CoA to succinate. Thus, 12 ATP molecules are generated for each turn of the cycle. 

 ATP production in mitochondria

Name of enzyme	Reaction Catalyzed	ATP molecules formed
Isocitrate dehydrogenase	Respiratory chain oxidation of NADH +H+	3
-Ketoglutrate dehydrogenase	Respiratory chain oxidation of NADH +H+	3
Succinate thiokinase	Phosphorylation at substrate level	1
Succinate dehydrogenase	Resiphorylation chain oxidation of FADH 2	2
Malate dehydrogenase	Respiratory chain oxidation of NADH +H+	3
	Net	12

Net ATP production from glucose

1. Glycolysis

One mole. of glucose → 2 moles of pyruvate

ATP produced                              =  8

 

2. Pyruvate → Acetyl CoA

ATP produced                              =  2x3=6

 

3. Citric acid cycle

Acetyl CoA →CO2 + H2O

ATP produced                              =  12 x2=24

 

Net production                           =30+8=38

 

Citric acid cycle intermediates are used for other metabolic purposes. It is an amphibolic pathway it functions not only in the oxidative degradation of carbohydrates, fatty acids and amino acids but also as a source of precursors for other metabolic pathways.