Summary As the above diagram illustrates, this is truly a continuous cycle. Acetyl coenzyme A binds to the oxaloacetate in order to convert it to citrate.
Water is released from the citrate and then regained in order to form isocitrate.
Coenzyme A leaves in order to form succinate. FAD binds to succinate and leaves as FADH2 in order to form fumarate. Water binds to fumarate and forms malate. NAD binds to malate and leaves as NADH which creates a new oxaloacetate molecule ready to bind to another acetyl coenzyme A to start the process over again. The electron transport system of mitochondria contains four large protein-based complexes that work in sequence to deliver electrons carried by NADH and FADH 2 to oxygen.