Krebs Cycle

Definition

The Krebs Cycle, also known as the citric acid cycle, is a series of chemical reactions used by all aerobic organisms to generate energy through the oxidation of acetyl-CoA. This cycle plays a crucial role in cellular respiration, linking glycolysis to the electron transport chain by producing electron carriers that are vital for ATP production. By processing pyruvate derived from glucose, the Krebs Cycle not only helps in energy production but also produces carbon dioxide as a waste product, which is expelled from the body.

5 Must Know Facts For Your Next Test

1. The Krebs Cycle occurs in the mitochondria of eukaryotic cells, making it essential for aerobic respiration.
2. Each turn of the Krebs Cycle generates three NADH molecules, one FADH2 molecule, and one ATP (or GTP) molecule.
3. Carbon dioxide is produced as a waste product during the Krebs Cycle, which is then transported to the lungs for exhalation.
4. The cycle is named after Hans Krebs, who first elucidated its biochemical pathways in 1937.
5. The Krebs Cycle is a crucial step in cellular metabolism, providing intermediates that can be used in various biosynthetic pathways.

Review Questions

• How does the Krebs Cycle connect glycolysis to the electron transport chain in cellular respiration?
  • The Krebs Cycle acts as a bridge between glycolysis and the electron transport chain by processing acetyl-CoA derived from pyruvate produced during glycolysis. As it runs, it generates key electron carriers, NADH and FADH2, which carry high-energy electrons to the electron transport chain. This connection ensures that the energy captured from glucose breakdown is efficiently utilized to produce ATP.
• Discuss the significance of the products generated by the Krebs Cycle in terms of energy production.
  • The products of the Krebs Cycle are vital for energy production in cells. Each turn of the cycle yields three NADH and one FADH2, both of which are critical for supplying electrons to the electron transport chain. This process ultimately leads to ATP synthesis through oxidative phosphorylation. Additionally, the ATP or GTP generated directly from the cycle serves immediate energy needs within the cell.
• Evaluate how disruptions in the Krebs Cycle could affect overall cellular respiration and metabolism.
  • Disruptions in the Krebs Cycle can significantly impair cellular respiration and overall metabolism. If any enzyme involved in the cycle is inhibited or dysfunctional, it can lead to decreased production of NADH and FADH2, resulting in less ATP being generated in the electron transport chain. This can cause energy deficits within cells and lead to metabolic disorders. Furthermore, accumulation of upstream metabolites can be toxic or indicate underlying pathologies, highlighting the critical role of a properly functioning Krebs Cycle in maintaining cellular health.

Related terms

Acetyl-CoA: A key molecule that enters the Krebs Cycle, formed from pyruvate and fatty acids, serving as the starting point for the cycle.

NADH:

An electron carrier produced during the Krebs Cycle that stores energy and delivers electrons to the electron transport chain.

FADH2: Another electron carrier produced during the Krebs Cycle, contributing to ATP generation in the electron transport chain.