The Krebs Cycle

Jun 4, 2024

The Krebs Cycle

Overview

  • The Krebs cycle further breaks down acetyl-CoA from the link reaction.
  • These acetyl-CoA molecules are derivatives of the original glucose molecule used at the beginning of respiration.
  • By completing the Krebs cycle, glucose is fully oxidized and converted to carbon dioxide.

Key Steps

Formation of Citric Acid

  • Acetyl-CoA reacts with a 4-carbon molecule, oxaloacetate, to form citric acid (6-carbon).
  • The Krebs cycle is also known as the Citric Acid Cycle due to this key molecule.

Oxidation Reactions

  1. Citric acid is oxidized, transferring electrons and hydrogens to NAD+ to form NADH.
    • This reaction releases CO2.
    • Result: 5-carbon molecule.
  2. The 5-carbon molecule undergoes further oxidation.
    • Produces another NADH and CO2.
    • Result: 4-carbon molecule.
  3. This 4-carbon molecule undergoes another chemical transformation, yielding ATP and converting to a different 4-carbon molecule.

Further Oxidation

  • The new 4-carbon molecule is oxidized again, transferring electrons and hydrogens to FAD, forming FADH2.
    • FADH2, like NADH, carries electrons to the electron transport chain.
  • The resulting molecule is oxidized once more to produce another NADH and reform oxaloacetate.
    • This completes the cycle, regenerating oxaloacetate to react with another acetyl-CoA.

Products Formed

  • NADH and FADH2: Electron carriers for the electron transport chain.
  • ATP: Usable energy for the cell.
  • CO2: Released as a waste product during exhaling.

Importance of the Krebs Cycle

  • Illustrates a cyclical process in cellular respiration.
  • Generates key molecules necessary for the electron transport chain and energy production.

Recommended Activity

  • For further learning, complete the respiration interactive activity at BioMan Biology.

Tip: Refer to the description of the activity for its length and details.

Additional Resources

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