For each molecule of acetyl coenzyme A that enters the Krebs cycle, it produces:

1. Reduced coenzymes (three molecules of reduced NAD and one molecule of reduced FAD)
2. One molecule of ATP
3. Two molecules of carbon dioxide

1. NAD participates in all stages of respiration, while FAD only accepts hydrogens in the Krebs cycle
2. NAD results in the synthesis of three ATP molecules, while FAD results in two ATP molecules

1. The 2C acetyl coenzyme A combines with the 4C oxaloacetate to form the 6C citrate
2. Citrate is decarboxylated, releasing two molecules of carbon dioxide
3. It is also dehydrogenated, releasing hydrogens that reduce three molecules of NAD and one molecule of FAD
4. ATP is synthesised from ADP and a phosphate group
5. Oxaloacetate is regenerated for the next cycle

Substrate-level phosphorylation in the Krebs cycle leads to the direct production of ATP.

The Krebs cycle (citric acid cycle) occurs in the mitochondrial matrix.

The coenzymes NAD and FAD pick up the hydrogens released during the Krebs cycle, forming reduced NAD and reduced FAD.

The reduced NAD and reduced FAD produced in the Krebs cycle are used in the final step of aerobic respiration to produce large quantities of ATP.

The ATP produced in the Krebs cycle is used by energy-requiring processes within the cell.

The carbon dioxide will either diffuse away and be removed from the organism as a metabolic waste, or it may be used as a raw material in photosynthesis.