Question

Why is a process as complex as the citric acid cycle actually an economical way for cells to do their metabolic business?

Answer 1

• The TCA cycle is the hub of intermediate metabolism. The 4 and 5 carbon products of many catabolic pathways feed into the TCA cycle as a source of fuel.
• Also, under certain metabolic condition the intermediates of the TCA cycle are drawn out of the pathway and serve as precursors to a variety of other biosynthetic pathways.
• The TCA cycle is amphibolic, meaning it serves both catbolic and anabolic purposes. The TCA cycle is not cofined to the oxidation of acetate. Even though it is not the shortest pathway from acetate to CO2 it confered the greatest biological advantage.
• The TCA cycle is the gateway to the aerobic metabolism of any molecule that can be transformed into an acetyl group or dicarboxylic acid. The cycle is also an important source of precursors, not only for the storage forms of fuels, but also for the building blocks of many other molecules such as amino acids, nucleotide bases, cholesterol, and porphyrin.