In the Citric Acid Cycle, which steps are responsible for the production of CO2?

In the Citric Acid Cycle (also known as the Krebs cycle), the production of carbon dioxide (CO2) occurs specifically during certain key steps. Steps 3 and 4 involve reactions that lead to the decarboxylation of intermediates, releasing CO2 as a byproduct.

In Step 3, isocitrate is converted to α-ketoglutarate. During this reaction, isocitrate undergoes oxidative decarboxylation, which means that one of its carboxyl groups is removed and released as CO2. This process is catalyzed by the enzyme isocitrate dehydrogenase and also produces NADH from NAD+.

Step 4 features the conversion of α-ketoglutarate to succinyl-CoA, another instance of oxidative decarboxylation. Here, α-ketoglutarate loses a carboxyl group as CO2, while also generating another molecule of NADH from NAD+ through its enzyme, α-ketoglutarate dehydrogenase complex.

Both of these steps are essential in completing the cycle and ensuring the proper flow of carbon through the metabolic pathways, highlighting their role in producing CO2 as a waste product of cellular respiration. Therefore,