Question

How many steps are involved in the TCA Cycle?

Answer 1

TCA cycle:

1. The TCA cycle is known as the tricarboxylic acid cycle.
2. It helps in generating energy-rich molecules such as NADH, ATP, FADH₂, etc.
3. It occurs in the mitochondrial matrix during aerobic cellular respiration.
4. The Pyruvate produced in the cytoplasm after glycolysis enters the mitochondria and is converted to acetyl CoA by oxidative decarboxylation.
5. The Acetyl CoA enters the TCA cycle.
6. TCA cycle has a total number of 8 steps.
7. The first step involves the conversion of Oxaloacetate to Citrate by the addition of H₂O and CoA via the enzyme Citrate synthase.
8. The citrate is then converted into Isocitrate via two successive reactions by the same enzyme Aconitase involving dehydration (removal of water) forming Cis-aconitase which is then converted into Isocitrate via hydration (addition of water).
9. Isocitrate is converted into Alpha-ketoglutarate by the enzyme Isocitrate dehydrogenase by the decarboxylation (removal of CO₂) reaction with the production of one molecule of NADH and H⁺.
10. Alpha-ketoglutarate is converted into Succinyl-CoA by the enzyme Alpha-ketoglutarate dehydrogenase via removing one molecule of CO₂ and producing one molecule of NADH and H⁺.
11. Coenzyme-A molecule is regenerated by the enzyme Succinyl-CoA synthetase by removing CoA from Succinyl-CoA and converting it into Succinate while producing one molecule of GTP.
12. Succinate is then converted to Fumarate by the enzyme Succinate dehydrogenase while generating a molecule of FADH₂.
13. Fumarate is hydrated to produce Malate by the enzyme Fumarase.
14. The last step in the cycle comprises of conversion of Malate to Oxaloacetate with the help of the enzyme Malate dehydrogenase producing one molecule of NADH and H⁺.