Krebs Cycle

Definition

The Krebs cycle, also known as the citric acid cycle or tricarboxylic acid (TCA) cycle, is a series of chemical reactions that occur in the mitochondria of cells. It is a key part of cellular respiration, where the energy stored in glucose and other organic molecules is released and used to produce ATP, the primary energy currency of the cell.

5 Must Know Facts For Your Next Test

1. The Krebs cycle is a cyclic pathway, meaning the end products of the cycle are used as the starting materials for the next turn of the cycle.
2. The Krebs cycle is the second stage of cellular respiration, occurring after glycolysis and before the electron transport chain and oxidative phosphorylation.
3. During the Krebs cycle, the acetyl group from acetyl-CoA is oxidized, releasing carbon dioxide and producing reduced coenzymes (NADH and FADH2) that are later used in the electron transport chain.
4. The Krebs cycle is a critical component of aerobic respiration, as it is the primary pathway for the complete oxidation of carbohydrates, fats, and proteins to carbon dioxide and water.
5. Regulation of the Krebs cycle is important for maintaining the balance between energy production and biosynthesis, as it provides precursors for the synthesis of various biomolecules.

Review Questions

• Explain the role of the Krebs cycle in the overall process of cellular respiration.
  • The Krebs cycle is the second stage of cellular respiration, occurring after glycolysis and before the electron transport chain and oxidative phosphorylation. During the Krebs cycle, the acetyl group from acetyl-CoA is oxidized, releasing carbon dioxide and producing reduced coenzymes (NADH and FADH2) that are later used in the electron transport chain to generate ATP. The Krebs cycle is a critical component of aerobic respiration, as it is the primary pathway for the complete oxidation of carbohydrates, fats, and proteins to carbon dioxide and water, providing the energy required for cellular processes.
• Describe the cyclic nature of the Krebs cycle and how it is regulated to maintain the balance between energy production and biosynthesis.
  • The Krebs cycle is a cyclic pathway, meaning the end products of the cycle are used as the starting materials for the next turn of the cycle. This cyclic nature allows for the continuous oxidation of acetyl-CoA, which is the primary fuel for the cycle. Regulation of the Krebs cycle is important for maintaining the balance between energy production and biosynthesis, as it provides precursors for the synthesis of various biomolecules. The cycle can be regulated by the availability of substrates, the activity of enzymes, and the levels of allosteric effectors, ensuring that the cycle operates efficiently to meet the cell's energy demands while also providing the necessary building blocks for cellular growth and repair.
• Analyze the significance of the Krebs cycle in the context of carbohydrate metabolism and explain how it is integrated with other metabolic pathways.
  • The Krebs cycle is a central metabolic pathway that is closely integrated with other metabolic processes, particularly carbohydrate metabolism. During cellular respiration, the Krebs cycle serves as the final common pathway for the complete oxidation of carbohydrates, fats, and proteins, converting their carbon skeletons into carbon dioxide and generating reduced coenzymes (NADH and FADH2) that are used in the electron transport chain to produce ATP. The Krebs cycle is also a source of various precursor molecules, such as oxaloacetate and α-ketoglutarate, which can be used in biosynthetic pathways for the production of amino acids, nucleotides, and other essential biomolecules. This integration of the Krebs cycle with other metabolic pathways ensures the efficient utilization of energy and the maintenance of cellular homeostasis.

Related terms

Cellular Respiration: The process by which cells convert the chemical energy in organic molecules, such as glucose, into a form that the cell can use, ATP.

Glycolysis:

The metabolic pathway that converts glucose into pyruvate, producing a small amount of ATP in the process.

Oxidative Phosphorylation: The process in which the energy released by the oxidation of nutrients is used to produce ATP.