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 derived from carbohydrates, fats, and proteins. This cycle plays a crucial role in cellular respiration by providing high-energy electron carriers that are essential for ATP production and connecting metabolic pathways, which relates directly to energy transformation and storage processes in biological systems.

5 Must Know Facts For Your Next Test

1. The Krebs Cycle occurs in the mitochondria of eukaryotic cells and is a central metabolic pathway in aerobic respiration.
2. For each acetyl-CoA molecule that enters the cycle, three NADH molecules, one FADH2 molecule, and one GTP (or ATP) are produced.
3. The cycle consists of eight enzyme-catalyzed reactions that result in the regeneration of oxaloacetate, allowing the cycle to continue.
4. The NADH and FADH2 produced are critical for the electron transport chain, where they donate electrons for ATP synthesis through oxidative phosphorylation.
5. The Krebs Cycle is not only involved in energy production but also serves as a hub for various metabolic pathways, providing intermediates for amino acid and lipid synthesis.

Review Questions

• How does the Krebs Cycle connect to other metabolic pathways in the cell?
  • The Krebs Cycle serves as a crucial metabolic hub where it interlinks with various pathways. It generates important intermediates such as oxaloacetate and alpha-ketoglutarate, which are not only part of the cycle but also serve as precursors for amino acids and other biomolecules. Additionally, the high-energy electron carriers produced during the cycle support ATP synthesis through oxidative phosphorylation, linking energy production directly to cellular metabolism.
• Discuss the importance of NADH and FADH2 produced during the Krebs Cycle in relation to ATP generation.
  • NADH and FADH2 are vital products of the Krebs Cycle that play an essential role in ATP generation through the electron transport chain. Each NADH can potentially yield about 2.5 ATP molecules, while each FADH2 can produce around 1.5 ATP molecules during oxidative phosphorylation. This means that the Krebs Cycle not only helps break down substrates for energy but also provides the necessary electron carriers that drive ATP production in cells.
• Evaluate how alterations in the Krebs Cycle can affect overall cellular metabolism and energy production.
  • Alterations in the Krebs Cycle can have profound effects on cellular metabolism and energy production. For instance, mutations in enzymes involved in the cycle may lead to reduced efficiency in ATP synthesis due to lower NADH and FADH2 output. This could result in impaired energy availability for cellular processes. Additionally, disruptions can lead to an accumulation of intermediates that may shift metabolic pathways towards fatty acid or amino acid synthesis instead of efficient energy production, ultimately impacting cellular health and function.

Related terms

Acetyl-CoA: A key molecule that enters the Krebs Cycle, formed from the breakdown of carbohydrates, fats, and proteins, serving as the starting substrate for the cycle.

NADH:

A high-energy electron carrier produced during the Krebs Cycle, essential for transporting electrons to the electron transport chain.

FADH2:

Another high-energy electron carrier generated during the Krebs Cycle, which also contributes to ATP production in the electron transport chain.