(1) Cellular Respiration Part 3: The Electron Transport Chain and Oxidative Phosphorylation

Overview of Oxidative Phosphorylation

  • Major step in cellular respiration following glycolysis and the citric acid cycle.

  • Generates the highest yield of ATP from glucose metabolism.

Key Processes in Oxidative Phosphorylation

Electron Transport Chain (ETC)

  • Located in the inner mitochondrial membrane.

  • Consists of protein complexes I-IV.

  • Functions: facilitate the transfer of electrons from NADH and FADH2.

  • Utilizes a series of redox reactions:

    • Electrons are shuttled from one complex to another.

    • Each successive complex has a higher affinity for electrons.

Role of Prosthetic Groups

  • Non-protein components of the protein complexes that enhance functionality.

  • Includes flavin mononucleotides and cytochromes.

  • Ubiquinone (Coenzyme Q): non-protein molecule that is mobile in the membrane.

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Generation of the Proton Gradient

  • Electrons from NADH enter complex I, initiating a chain reaction.

  • During electron transfer, protons (H+) are pumped from the mitochondrial matrix to the intermembrane space.

  • Result: Proton gradient established across the inner mitochondrial membrane.

ATP Synthase

  • Protein complex responsible for synthesizing ATP.

  • Operates via chemiosmosis:

    • Protons flow back into the mitochondrial matrix through ATP synthase, driven by the proton-motive force.

  • Structure resembles a rotor:

    • Protons binding induce rotation, catalyzing ADP phosphorylation to form ATP.

  • Effectiveness: Each glucose molecule can yield approximately 26 - 28 ATPs from this pathway.

Summary of Cellular Respiration Pathways

  • Glycolysis:

    • Produces 2 ATP and pyruvate from glucose.

  • Citric Acid Cycle:

    • Processes pyruvate to generate 2 ATP, 6 NADH, and 2 FADH2.

  • Oxidative Phosphorylation:

    • Utilizes NADH and FADH2 to produce the majority of ATP.

Metabolism of Other Food Sources

  • Other macromolecules (proteins, fats, carbohydrates) break down uniquely but ultimately feed into the same pathways discussed.

  • All nutrients ultimately contribute to ATP generation in the mitochondria.

Conclusion

  • Mitochondria are the powerhouse of the cell, essential for energy production.

  • ATP production supports cellular activities, critical for maintaining life processes.