Citric Acid Cycle — Prelims Strategy

Prelims Strategy

To effectively tackle NEET questions on the Citric Acid Cycle, a multi-pronged strategy is essential. Firstly, memorize the sequence of intermediates and the key enzymes involved in each step. A simple mnemonic can be highly effective for recalling the order of molecules.

Secondly, focus on the energy yield at each step: identify where NADH, FADH2, and GTP (or ATP) are produced, and how many of each per Acetyl-CoA. Understand that the majority of ATP comes indirectly from NADH and FADH2 via the Electron Transport System.

Thirdly, pay close attention to the regulatory points – which enzymes are inhibited by high ATP/NADH and activated by high ADP/Ca2+. Fourthly, grasp the amphibolic nature of the cycle, knowing which intermediates serve as precursors for other biomolecules (e.

g., citrate for fatty acids, $\alpha$-ketoglutarate for amino acids). For numerical problems, practice calculating the total ATP yield from a given number of glucose or Acetyl-CoA molecules, considering the contributions from glycolysis, pyruvate oxidation, and the CAC.

Always read the question carefully to distinguish between yield per glucose and yield per Acetyl-CoA. Finally, be aware of common misconceptions, such as the direct oxygen requirement or direct ATP production, to avoid trap options.