Lecture Notes: Oxidative Phosphorylation

Overview of Cellular Respiration

• Oxidative Phosphorylation: Final major step in cellular respiration.
  • Involves two key components:
    • Electron Transport Chain (ETC)
    • Chemiosmosis

ATP Production Before Oxidative Phosphorylation

• Glycolysis: 2 ATP
• Citric Acid Cycle: 2 ATP
• Total ATP so far: 4 ATP
• High Energy Electron Carriers:
  • Glycolysis and Transition Phase: 4 NADH
  • Citric Acid Cycle: 6 NADH, 2 FADH2

Electron Transport Chain (ETC)

• Purpose: Convert energy from NADH and FADH2 to transport hydrogen ions against their concentration gradient.
• Process:
  • Electrons from NADH and FADH2 passed through protein complexes.
  • Protein Complexes: Act like a "hot potato," passing electrons and losing energy.
  • Energy Usage: Used for transporting hydrogen ions to the intermembrane space, creating a gradient.
  • Final Electron Acceptor: Oxygen, forming water.
  • Outcome: Establishes a proton gradient, no ATP directly produced.

Chemiosmosis

• Role of ATP Synthase: Acts like a water wheel.
  • Converts potential energy from proton gradient to kinetic energy, producing ATP.
• Requirement: Aerobic process, requiring oxygen.
• Outcome: Production of ATP through the kinetic energy of moving protons.

Anaerobic vs. Aerobic Metabolism

• Anaerobic Metabolism:
  • Only glycolysis functions.
  • Produces a net of 2 ATP.
  • Involves fermentation to recycle co-enzymes.
• Aerobic Metabolism:
  • Total ATP: 30-32 (eukaryotes), 36-38 (bacteria)
  • Complete oxidative phosphorylation and recycling of NAD+ and FAD.

Misconceptions and Clarifications

• The ETC does not produce ATP; it establishes a gradient used in chemiosmosis.
• Textbooks may incorrectly attribute ATP production to ETC alone.

Poison Effects on Cellular Respiration

• Types of Poisons:
  • Block ETC (e.g., cyanide, carbon monoxide): Prevents proton gradient formation.
  • Inhibit ATP Synthase (e.g., oligomycin): Reduces ATP production.
  • Increase Membrane Permeability (e.g., DNP): Affects gradient maintenance.