What is the conversion that occurs in Step 3 of the Citric Acid Cycle?

In Step 3 of the Citric Acid Cycle, the conversion that occurs is the transformation of Isocitrate to α-ketoglutarate. This reaction is catalyzed by the enzyme isocitrate dehydrogenase, and it is a crucial step in the cycle as it represents the first oxidative decarboxylation, meaning that it involves both oxidation and the removal of a carbon dioxide molecule.

During this process, isocitrate is oxidized, leading to the reduction of NAD+ to NADH. The decarboxylation that follows generates α-ketoglutarate, a five-carbon compound. This step is not only significant for its role in energy production but also provides key intermediates for various biosynthetic pathways, highlighting its importance in cellular metabolism.

The other options represent different reactions occurring at various stages of the Citric Acid Cycle, but they do not describe the reaction in Step 3 involving isocitrate. Thus, understanding the specific transformations and the enzymes involved in this cycle is fundamental for grasping how carbohydrate metabolism feeds into energy production.