Oxaloacetate

Definition

Oxaloacetate is a key intermediate in the citric acid cycle, also known as the Krebs cycle, which is a central metabolic pathway in cellular respiration. It serves as an important link between carbohydrate, fat, and protein metabolism, playing a crucial role in energy production within the cell.

5 Must Know Facts For Your Next Test

1. Oxaloacetate is a four-carbon dicarboxylic acid that serves as a key intermediate in the citric acid cycle.
2. It is produced from the carboxylation of pyruvate by the enzyme pyruvate carboxylase, which is an anaplerotic reaction that replenishes the cycle.
3. Oxaloacetate condenses with acetyl-CoA to form citrate, the first step in the citric acid cycle, which is the central pathway for the oxidation of acetyl-CoA derived from the breakdown of carbohydrates, fats, and some amino acids.
4. Oxaloacetate can also be produced from the transamination of aspartate, providing another anaplerotic input to the citric acid cycle.
5. The concentration of oxaloacetate is tightly regulated by the cell, as it plays a critical role in controlling the rate of the citric acid cycle and overall cellular energy production.

Review Questions

• Explain the role of oxaloacetate in the citric acid cycle and its importance in cellular energy production.
  • Oxaloacetate is a key intermediate in the citric acid cycle, which is the central metabolic pathway for the oxidation of acetyl-CoA derived from the breakdown of carbohydrates, fats, and some amino acids. Oxaloacetate condenses with acetyl-CoA to form citrate, the first step in the cycle. The citric acid cycle then generates NADH and FADH2, which are used by the electron transport chain to produce ATP, the primary energy currency of the cell. The concentration of oxaloacetate is tightly regulated, as it plays a critical role in controlling the rate of the citric acid cycle and overall cellular energy production.
• Describe the anaplerotic reactions that replenish the citric acid cycle intermediates, including the role of oxaloacetate.
  • Anaplerotic reactions are those that replenish the intermediates of the citric acid cycle, such as oxaloacetate. One such reaction is the carboxylation of pyruvate by the enzyme pyruvate carboxylase to form oxaloacetate. This reaction provides a crucial input to the cycle, as oxaloacetate then condenses with acetyl-CoA to form citrate, the first step in the citric acid cycle. Oxaloacetate can also be produced from the transamination of aspartate, providing another anaplerotic input to the cycle. These anaplerotic reactions help maintain the appropriate concentrations of citric acid cycle intermediates, ensuring the efficient oxidation of acetyl-CoA and the continued production of NADH and FADH2 for ATP synthesis.
• Analyze the interconnectedness of oxaloacetate with the metabolism of carbohydrates, fats, and amino acids, and explain how this contributes to the central role of the citric acid cycle in cellular energy production.
  • Oxaloacetate serves as a critical link between the metabolism of carbohydrates, fats, and amino acids within the citric acid cycle. Carbohydrate metabolism provides pyruvate, which can be carboxylated to form oxaloacetate, an anaplerotic reaction that replenishes the cycle. Fat metabolism produces acetyl-CoA, which then condenses with oxaloacetate to form citrate, the first step in the citric acid cycle. Amino acid metabolism can also contribute to the pool of oxaloacetate through transamination reactions. The centrality of the citric acid cycle, with oxaloacetate as a key intermediate, allows for the efficient oxidation of these various metabolic inputs to generate NADH and FADH2, which drive the electron transport chain and ultimately lead to the production of ATP, the primary energy currency of the cell. This interconnectedness highlights the crucial role of oxaloacetate in coordinating cellular energy production from diverse metabolic pathways.

Related terms

Citric Acid Cycle:

The cyclic pathway that oxidizes acetyl-CoA to carbon dioxide, generating NADH and FADH2 to drive the electron transport chain and ATP synthesis.

Acetyl-CoA:

The central metabolic intermediate that enters the citric acid cycle and is produced from the breakdown of carbohydrates, fats, and some amino acids.

Anaplerotic Reactions:

Reactions that replenish the intermediates of the citric acid cycle, such as the conversion of pyruvate to oxaloacetate.