Question

Name the reactions in the citric acid cycle that involve oxidative decarboxylation.

Accepted Answer

Step 1: Understand the term 'oxidative decarboxylation'. This refers to a chemical reaction where a molecule is oxidized (loses electrons) and a carboxyl group (-COOH) is removed as carbon dioxide (CO₂). These reactions are key steps in metabolic pathways like the citric acid cycle. Step 2: Recall the citric acid cycle (also known as the Krebs cycle or TCA cycle). It is a series of enzymatic reactions that occur in the mitochondria, playing a central role in cellular respiration by oxidizing acetyl-CoA to CO₂ and generating energy-rich molecules like NADH and FADH₂. Step 3: Identify the specific reactions in the citric acid cycle that involve oxidative decarboxylation. These are the steps where both oxidation and the release of CO₂ occur. The two key reactions are: (1) the conversion of isocitrate to α-ketoglutarate, catalyzed by isocitrate dehydrogenase, and (2) the conversion of α-ketoglutarate to succinyl-CoA, catalyzed by α-ketoglutarate dehydrogenase. Step 4: For the first reaction, isocitrate is oxidized to form oxalosuccinate, which then undergoes decarboxylation to produce α-ketoglutarate. This reaction also reduces NAD⁺ to NADH. The overall reaction can be written as: isocitrate + $$NAD^{+}$$ → α-ketoglutarate + $$NADH^{+} + CO2. $$Step 5: For the second reaction, α-ketoglutarate is oxidized and decarboxylated to form succinyl-CoA. This reaction also reduces NAD⁺ to NADH. The overall reaction can be written as: α-ketoglutarate + $$NAD^{+} + $$CoA → succinyl-CoA + $$NADH^{+} + CO2.$$

Name the reactions in the citric acid cycle that involve oxidative decarboxylation.

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Key Concepts

Citric Acid Cycle

Oxidative Decarboxylation

Key Reactions in the Citric Acid Cycle