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Understanding the Krebs Cycle in Detail

Apr 26, 2025

Krebs Cycle Lecture Notes

Overview

  • The Krebs cycle, also known as the citric acid cycle, is a series of chemical reactions used in cellular respiration.
  • It's designed to completely oxidize acetyl-CoA, derived from glucose, into carbon dioxide.
  • The cycle results in the production of electron carriers (NADH and FADH2), ATP, and CO2.
  • Takes place in the mitochondria after glycolysis and the link reaction.

Key Steps in the Krebs Cycle

Formation of Citric Acid

  • Acetyl-CoA: Begins the cycle by combining with a 4-carbon molecule, oxaloacetate.
  • Citric Acid: This reaction forms a 6-carbon molecule called citric acid.
  • Cycle Name: Named after this molecule, the cycle is sometimes called the citric acid cycle.

Oxidation Reactions and Energy Extraction

  1. Citric Acid Oxidation:
    • Citric acid is oxidized, transferring electrons and hydrogens to NAD+ to form NADH.
    • CO2 Released: This oxidation reaction releases CO2, leaving a 5-carbon molecule.
  2. Further Oxidation:
    • Similar oxidation occurs, producing another NADH and releasing another CO2.
    • Results in a 4-carbon molecule.
  3. ATP Formation:
    • The 4-carbon molecule undergoes a chemical reaction, releasing energy.
    • This energy combines ADP and phosphate to form ATP.
  4. FADH2 Formation:
    • The remaining 4-carbon molecule is further oxidized, forming FADH2.
    • FADH2 functions like NADH, carrying electrons to the electron transport chain.
  5. Final Oxidation:
    • Additional oxidation produces more NADH.
    • Regenerates the starting molecule, oxaloacetate, completing the cycle.

Importance

  • Electron Carriers: The cycle creates NADH and FADH2, crucial for electron transport chain.
  • ATP Production: Provides a direct source of energy for cells.
  • CO2 Production: CO2 is produced as a waste product.

Conclusion

  • The cycle repeats as long as there are acetyl-CoA molecules available.
  • Supports cellular respiration by supplying electron carriers for the electron transport chain.

Additional Resources

  • For interactive learning, check out resources like respiration activities at Bioman Biology.
  • Additional support: videos, quizzes, and learning tools available at Bioman Biology website.

If engaging in an interactive activity, refer to the provided description for instructions. Always refer back for additional tasks related to the Krebs Cycle.

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