Citrate

Definition

Citrate is a key intermediate in the citric acid cycle, also known as the Krebs cycle, formed from the condensation of acetyl-CoA and oxaloacetate. It plays a vital role in cellular respiration by participating in a series of enzymatic reactions that lead to energy production through the oxidation of acetyl-CoA. The regulation of citrate levels can influence the citric acid cycle and is interconnected with various metabolic pathways, highlighting its importance in energy metabolism.

5 Must Know Facts For Your Next Test

1. Citrate is formed when acetyl-CoA condenses with oxaloacetate in the first step of the citric acid cycle, catalyzed by the enzyme citrate synthase.
2. Citrate can be converted into isocitrate through an enzymatic rearrangement, which is essential for its further oxidation and energy extraction.
3. High levels of citrate can inhibit phosphofructokinase-1 (PFK-1), an important regulatory enzyme in glycolysis, linking carbohydrate metabolism to the citric acid cycle.
4. Citrate serves as a signaling molecule in various metabolic pathways, influencing lipid synthesis and gluconeogenesis.
5. In conditions where citrate accumulates, it can be transported out of the mitochondria into the cytoplasm, where it may contribute to fatty acid synthesis.

Review Questions

• How does citrate formation link carbohydrate metabolism to energy production?
  • Citrate formation occurs when acetyl-CoA combines with oxaloacetate at the beginning of the citric acid cycle. This reaction signifies the transition from glycolysis, where carbohydrates are broken down to produce acetyl-CoA, to the citric acid cycle, where citrate undergoes further oxidation to generate ATP and other high-energy molecules. The connection highlights how carbohydrates ultimately contribute to cellular energy production through citrate.
• Discuss the regulatory role of citrate within metabolic pathways and its impact on glycolysis.
  • Citrate acts as an important regulator within metabolic pathways by influencing key enzymes such as phosphofructokinase-1 (PFK-1) in glycolysis. When citrate levels are high, it signals that there is enough energy available, leading to the inhibition of PFK-1. This feedback mechanism helps to prevent excessive glucose breakdown when energy needs are met, thereby maintaining metabolic balance and efficiency.
• Evaluate the significance of citrate's role in integrating various metabolic pathways and its implications for overall energy homeostasis.
  • Citrate plays a crucial role in integrating multiple metabolic pathways by acting as a signaling molecule that connects the citric acid cycle with lipid synthesis and gluconeogenesis. Its accumulation not only indicates sufficient energy supply but also influences other metabolic processes by promoting fatty acid synthesis or inhibiting glycolysis. This interconnectivity underscores citrate's importance in maintaining energy homeostasis within cells and demonstrates how shifts in one pathway can significantly impact overall metabolism.

Related terms

Acetyl-CoA: A central metabolite that serves as a key substrate for the citric acid cycle, derived from carbohydrates, fats, and proteins.

Oxaloacetate: A four-carbon molecule that combines with acetyl-CoA to form citrate, serving as a crucial starting point for the citric acid cycle.

ATP: A high-energy molecule produced during the citric acid cycle, serving as the primary energy currency of the cell.