That's the citric acid cycle, also known as the Krebs cycle, also known as the TCA (tricarboxylic acid cycle). It is one of a series of enzyme reaction pathways used in the conversion of carbon compounds to energy in the respiration of higher animals. The cycle takes place in the mitochondria, uses 8 different enzymes plus a number of coenzymes, and involves the concerted action of other components, like the translocases which provide the necessary compounds to the mitochondria, and the PDH complex which provides the oxidation product from pyruvate for the cycle. It's an open cycle, meaning that the steps in the cylce are used for other reactions as well.
I hope this all sounds sufficiently complex. General_re, I'm sure can fill you in on these facts as well, Diamond.