Lecture 12: Biochemistry - Electron Transport Chain and Oxidative Phosphorylation

Learning Objectives

• Describe the key components of the electron transport chain (ETC)
  • Understand enzyme complexes and electron carriers.
• Explain benefits of the ETC being membrane-bound
  • Allows for proton gradient buildup, creating a proton motive force.
• Describe conversion of proton motive force to ATP
  • Understand composition and function of ATP synthase (F0 and F1 subunits).
  • Role of C-ring and gamma subunit in ATP catalysis.
• Identify determinant of cellular respiration rate
  • Primarily driven by ATP demand.

Overview of Electron Transport Chain (ETC) and Oxidative Phosphorylation

• Purpose: Convert energy from electron carriers (NADH, FADH2) into ATP.
• Components:
  • Complexes I-IV: Membrane-bound complexes facilitating electron transfer and proton pumping.
  • Electron Carriers: NADH and FADH2 generated in glycolysis, pyruvate dehydrogenase, and TCA cycle.
  • Final Electron Acceptor: Oxygen (O2 converted to water with protons and electrons).

Electron Transport Chain Process

• Complex I: NADH donates electrons, regenerating NAD+, pumps 4 protons.
• Complex II: FADH2 donates electrons, no protons pumped.
• Complex III: Transfers electrons from coenzyme Q to cytochrome C, pumps 4 protons.
• Complex IV: Transfers electrons to oxygen, converting it to water, pumps 2 protons.

Proton Gradient and ATP Synthesis

• Proton Gradient: Created by electron flow through complexes, pumping protons into the intermembrane space.
• Role of ATP Synthase:
  • C-ring rotation: Driven by proton movement, spins gamma subunit.
  • Conformational changes: Induce ATP synthesis from ADP and phosphate.

Energetics of ETC

• NADH: Pumps 10 protons, equivalent to 2.5 ATP.
• FADH2: Pumps 6 protons, equivalent to 1.5 ATP.
• ATP Generation:
  • 4 protons required per ATP synthesized.
  • Total from glucose metabolism: 32 ATP.

Key Concepts

• Redox Reactions: Series of electron transfers reducing O2 to H2O.
• Proton Motive Force: Electrochemical gradient used for ATP production.
• Importance of Membranes: Compartmentalization crucial for gradient and ATP synthase function.

Videos and Additional Resources

• Recommended videos for further understanding of ETC and ATP synthesis.
• Suggested activities: Diagram pathways of ATP extraction from carbohydrate sources.

Next Steps: Review provided video resources for detailed visualization of processes and prepare questions for class discussions.