Lecture Notes: Oxidative Phosphorylation

Overview

• Cellular Respiration Steps:
  • Glycolysis
  • Citric Acid Cycle
  • Oxidative Phosphorylation (main focus)
• Purpose: Generate most ATP in cellular respiration.

Electron Transport Chain

• Location: Inner mitochondrial membrane
• Components:
  • Protein Complexes: I-IV
  • Prosthetic Groups: Non-protein components giving functionality (e.g., flavin mononucleotides, cytochromes)
  • Non-Protein Compound:
    • Ubiquinone (Coenzyme Q): Small, hydrophobic, mobile within the membrane

Process of Electron Transport

• Electron Source: NADH and FADH2 from Citric Acid Cycle
• Mechanism:
  • Electrons fed into Complex I
  • Series of redox reactions
  • Electrons move downhill through chain
  • Higher electron affinity with each component
• Result: Generates a proton gradient (not ATP directly)

ATP Synthesis via Chemiosmosis

• Proton Gradient:
  • Accumulation outside inner mitochondrial membrane
  • Drives protons through ATP synthase
• ATP Synthase:
  • Function: Phosphorylates ADP to ATP
  • Structure: Rotor-like component, protons bind and cause spinning
• Terminology:
  • Chemiosmosis: Process of protons moving with gradient
  • Proton-Motive Force: Energy from proton gradient

Energy Yield

• From One Glucose Molecule: Approximately 26-28 ATP
• Comparison: Most ATP comes from this pathway

Summary of Metabolic Pathways

• Glycolysis:
  • ATP yield: 2 per glucose
  • Produces pyruvate for Citric Acid Cycle
• Citric Acid Cycle:
  • ATP yield: 2 per pyruvate
  • Produces 6 NADH, 2 FADH2
• Electron Transport Chain: Provides major ATP payout

Other Food Sources

• Proteins, fats, and other carbohydrates eventually feed into these pathways

Mitochondrial Function

• Role: Engine of the cell
• Importance: Primary source of energy for cellular activity

Conclusion

• Cellular respiration is the process powering movement and energy use.
• Reminder: Enzymes in mitochondria are critical for energy production.