Krebs Cycle

Definition

The Krebs Cycle, also known as the citric acid cycle or TCA cycle, is 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. This cycle plays a critical role in cellular respiration, linking the breakdown of biological macromolecules—carbohydrates, lipids, and proteins—to the production of ATP, the primary energy currency of the cell.

5 Must Know Facts For Your Next Test

1. The Krebs Cycle occurs in the mitochondria of eukaryotic cells, where it serves as a central hub for energy metabolism.
2. For each turn of the Krebs Cycle, three NADH, one FADH2, and one GTP (or ATP) are produced, contributing to the overall energy yield during cellular respiration.
3. The cycle begins with the combination of acetyl-CoA and oxaloacetate to form citric acid, which then undergoes a series of transformations and decarboxylation reactions.
4. The NADH and FADH2 generated during the Krebs Cycle are essential for powering the electron transport chain, leading to further ATP production.
5. The Krebs Cycle not only contributes to energy production but also provides intermediates for the biosynthesis of important biomolecules such as amino acids and nucleotides.

Review Questions

• How does the Krebs Cycle integrate with other metabolic pathways in cellular respiration?
  • The Krebs Cycle acts as a crucial link between various metabolic pathways by processing acetyl-CoA derived from carbohydrates, lipids, and proteins. This integration allows cells to efficiently utilize different macromolecules for energy production. As these macromolecules are broken down through glycolysis or beta-oxidation, they feed into the Krebs Cycle, enabling the cell to maximize its energy output based on available nutrients.
• Discuss the significance of NADH and FADH2 produced during the Krebs Cycle in terms of their role in ATP synthesis.
  • NADH and FADH2 produced in the Krebs Cycle are vital for ATP synthesis as they serve as electron carriers that feed into the electron transport chain. In this process, electrons from NADH and FADH2 are transferred through a series of protein complexes in the mitochondrial membrane. This transfer generates a proton gradient that drives ATP synthase to produce ATP through oxidative phosphorylation, significantly increasing the total energy yield from glucose metabolism.
• Evaluate how disruptions in the Krebs Cycle can affect overall cellular metabolism and homeostasis.
  • Disruptions in the Krebs Cycle can have profound effects on cellular metabolism and homeostasis by hindering energy production and disrupting critical biosynthetic pathways. For instance, if any enzymes involved in the cycle are inhibited or malfunctioning, it can lead to decreased ATP levels and accumulation of metabolites. This imbalance can trigger metabolic disorders and affect cellular functions, highlighting the importance of a properly functioning Krebs Cycle for maintaining energy balance and overall cell health.

Related terms

Acetyl-CoA: A molecule that serves as a key intermediate in various metabolic pathways, formed from carbohydrates, fats, and proteins and entering the Krebs Cycle.

ATP (Adenosine Triphosphate): The main energy carrier in cells, produced during the Krebs Cycle and used for various cellular processes.

NADH: A coenzyme that functions as an electron carrier in the Krebs Cycle, playing a crucial role in energy production through oxidative phosphorylation.