Krebs Cycle

Definition

The Krebs Cycle, also known as the citric acid cycle or tricarboxylic acid (TCA) cycle, is a series of chemical reactions used by all aerobic organisms to generate energy through the oxidation of acetyl-CoA. It plays a crucial role in cellular respiration by producing energy-rich compounds like ATP, NADH, and FADH2, which are essential for fueling various biological processes. Additionally, it serves as a central hub in metabolism, linking carbohydrate, fat, and protein metabolism together.

5 Must Know Facts For Your Next Test

1. The Krebs Cycle occurs in the mitochondria of cells and consists of eight distinct steps, each catalyzed by specific enzymes.
2. During each turn of the cycle, one acetyl-CoA molecule is oxidized, resulting in the production of two molecules of carbon dioxide, three molecules of NADH, one molecule of FADH2, and one molecule of ATP or GTP.
3. The cycle begins with the combination of acetyl-CoA and oxaloacetate to form citrate, which undergoes a series of transformations that regenerate oxaloacetate for the next cycle.
4. The NADH and FADH2 generated in the Krebs Cycle carry high-energy electrons to the electron transport chain, where their energy is used to produce a significant amount of ATP.
5. The Krebs Cycle is not only critical for energy production but also provides intermediates for biosynthetic pathways, making it essential for the synthesis of amino acids and other important biomolecules.

Review Questions

• How does the Krebs Cycle integrate different metabolic pathways within the cell?
  • The Krebs Cycle serves as a central hub in cellular metabolism by connecting various pathways such as carbohydrate, fat, and protein metabolism. Acetyl-CoA, which enters the cycle, can be derived from glucose through glycolysis or from fatty acids and amino acids during their breakdown. This integration allows for efficient energy production and resource allocation based on the cell's needs.
• Discuss the importance of NADH and FADH2 produced in the Krebs Cycle for ATP production.
  • NADH and FADH2 are crucial byproducts of the Krebs Cycle that carry high-energy electrons to the electron transport chain during oxidative phosphorylation. The transfer of these electrons releases energy used to pump protons across the mitochondrial membrane, creating a proton gradient. This gradient drives ATP synthesis through ATP synthase, making NADH and FADH2 key players in maximizing ATP yield from cellular respiration.
• Evaluate how disruptions in the Krebs Cycle could affect overall cellular function and health.
  • Disruptions in the Krebs Cycle can lead to decreased ATP production, which impairs cellular functions that require energy. A lack of intermediates may also affect biosynthetic processes essential for producing amino acids and other biomolecules. These disruptions can result from metabolic disorders or nutrient deficiencies, ultimately leading to cellular dysfunctions that manifest as various health issues, including fatigue, muscle weakness, and compromised immune response.

Related terms

Acetyl-CoA: A molecule that acts as a key intermediate in the Krebs Cycle, derived from carbohydrates, fats, and proteins, and is crucial for energy production.

NADH:

A coenzyme that carries electrons to the electron transport chain after being produced in the Krebs Cycle, playing a critical role in ATP production.

Oxidative Phosphorylation:

The final stage of cellular respiration where ATP is produced using the energy from electrons transferred through the electron transport chain, which is powered by products from the Krebs Cycle.