Textbook - BIOLOGICAL CHEMISTRY - Hubsky Y.I. - 2000

Chapter II. GENERAL PRINCIPLES OF METABOLISM

CHAPTER 10. TRICARBOXYLIC ACID CYCLE

10.3. ENERGY BALANCE OF THE TRICARBOXYLIC ACID CYCLE

The biochemical result of The Tricarboxylic Acid Cycle involves The formation of two CO₂ molecules (in the isocitrate dehydrogenase and α-ketoglutarate dehydrogenase reactions) and four pairs of hydrogen atoms, three of which are accepted by NAD⁺ and one by FAD. The reduced Coenzymes are oxidized in the mitochondrial Respiratory Chain, yielding, through Oxidative Phosphorylation, 3 ATP molecules for each NADH molecule and 2 ATP molecules for each FADH₂ molecule. In addition, one ATP molecule is produced via substrate-level phosphorylation during The conversion of succinyl-CoA to succinate (Table 10.1).

Class="center">Table 10.1. Summary balance of ATP molecules generated during the functioning of the citrate cycle

Reaction	Coenzyme	Number of ATP molecules formed
1. Isocitrate — α-ketoglutarate	NAD	3
2. α-ketoglutarate — succinyl-CoA	NAD	3
3. Succinyl-CoA — succinate	GDP	1
4. Succinate — fumarate	FAD	2
5. Malate — oxaloacetate	NAD	3
Total		12

Thus, the Complete oxidation of one acetyl-CoA molecule to CO₂ and H₂O in the tricarboxylic acid cycle generates 12 ATP molecules.

Last update: 06/08/2026

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