Oxidative decarboxylation

Definition

Oxidative decarboxylation is a biochemical reaction where a carboxyl group is removed from a molecule, releasing carbon dioxide (CO₂) and transferring electrons to electron carriers. This process is crucial in energy production as it links glycolysis and the citric acid cycle, facilitating the conversion of pyruvate into acetyl-CoA, a key substrate for energy generation.

5 Must Know Facts For Your Next Test

1. Oxidative decarboxylation occurs in the mitochondria, where pyruvate is converted into acetyl-CoA by the pyruvate dehydrogenase complex.
2. This reaction releases one molecule of carbon dioxide (CO₂), reducing the carbon skeleton by one carbon atom.
3. NAD+ is reduced to NADH during oxidative decarboxylation, which later contributes to ATP production in the electron transport chain.
4. The conversion of pyruvate to acetyl-CoA through this process is an irreversible step, meaning it cannot be reversed in metabolic pathways.
5. Oxidative decarboxylation not only plays a key role in energy metabolism but also links carbohydrate metabolism to fatty acid synthesis.

Review Questions

• How does oxidative decarboxylation contribute to the transition between glycolysis and the citric acid cycle?
  • Oxidative decarboxylation serves as a critical bridge between glycolysis and the citric acid cycle by converting pyruvate, the end product of glycolysis, into acetyl-CoA. During this process, a carboxyl group is removed and released as carbon dioxide, while electrons are transferred to NAD+, forming NADH. This transformation ensures that acetyl-CoA can enter the citric acid cycle, where it undergoes further oxidation for energy production.
• Discuss the role of coenzymes in oxidative decarboxylation and their impact on metabolic pathways.
  • Coenzymes such as NAD+ play an essential role in oxidative decarboxylation by acting as electron carriers. During the conversion of pyruvate to acetyl-CoA, NAD+ accepts electrons and is reduced to NADH. This reduction not only aids in the oxidative process but also links oxidative decarboxylation to other metabolic pathways, including the electron transport chain, where NADH contributes to ATP production. Thus, coenzymes facilitate energy transfer and metabolic regulation.
• Evaluate how the process of oxidative decarboxylation influences both energy production and biosynthetic pathways in cellular metabolism.
  • Oxidative decarboxylation significantly impacts energy production by generating acetyl-CoA, which enters the citric acid cycle for ATP synthesis. Additionally, the process generates NADH, enhancing electron transport and further ATP generation. Beyond energy production, acetyl-CoA serves as a pivotal precursor for biosynthetic pathways, including fatty acid synthesis and cholesterol biosynthesis. This dual role highlights how oxidative decarboxylation integrates energy metabolism with cellular growth and maintenance needs.

Related terms

Citric Acid Cycle: A series of chemical reactions used by all aerobic organisms to generate energy through the oxidation of acetyl-CoA derived from carbohydrates, fats, and proteins.

NAD+: Nicotinamide adenine dinucleotide, a coenzyme that plays a critical role in redox reactions, accepting electrons during metabolic processes.

Pyruvate: The end product of glycolysis that is converted into acetyl-CoA through oxidative decarboxylation before entering the citric acid cycle.