18.3 the Krebs cycle

where does the Krebs cycle take place

in the mitochondrial matrix

stages of the Krebs cycle

• Acetyl CoA delivers an acetyl group to the Krebs cycle. The two carbon acetyle group combines with 4 carbon oxaloacetate to form 6 carbon citrate

• this citrate molecule undergoes decarboxylation and dehydrogenation producing one reduced NAD and carbon dioxide. A 5-carbon compound is formed

• the 5 carbon compound undergoes further decarboxylation and dehydrogenation reactions, eventually regenerating oxaloacetate 

what is produced during the Kreb cycle

3 NADH

1 FADH

2 carbon dioxide (waste product)

1 ATP molecule

differences between NAD and FAD

• FAD is only involved in the Kreb cycle

• NAD accepts one hydrogen and FAD accepts two hydrogens

• reduced NAD is oxidised at the start of the electron transport chain releases protons and electrons while reduced FAD is oxided further along the chain

• reduced NAD results in the synthesis of 3 ATP molecules while reduced FAD results in the synthesis of only 2 ATP molecules