Electron Transport Chain Lecture Notes

Overview

• Focuses on the role of the electron transport chain (ETC) in cellular respiration.
• Explains how NADH and FADH2 contribute to ATP production.
• Highlights the energy release when electrons transfer from high to low energy states, creating a proton gradient that powers ATP synthase.

Key Components

• NADH and FADH2: Play crucial roles in providing electrons to the ETC.
  • NADH: Responsible for producing 3 ATPs each.
  • FADH2: Responsible for producing 2 ATPs each.
  • Electrons from NADH and FADH2 enter the ETC at different energy levels.

Electron Transport Chain Process

1. Oxidation of NADH

   • NADH is oxidized to NAD+, releasing two electrons.
   • Electrons are transferred through a series of molecules (e.g., coenzyme Q, cytochrome C) to reduce oxygen into water.

2. Energy Release

   • As electrons transition to lower energy states, energy is released.
   • This energy is used to pump protons (H+) across the mitochondrial inner membrane.

3. Proton Gradient Formation

   • Results in a higher concentration of protons in the outer compartment.
   • Creates an electrochemical gradient (proton-motive force).

4. ATP Synthesis

   • Protons flow back into the matrix through ATP synthase.
   • The flow of protons drives ATP synthase to convert ADP and phosphate into ATP.

ATP Production

• Total ATP yield from glucose breakdown:
  • Glycolysis: 2 net ATP
  • Krebs Cycle: 2 ATP
  • ETC and Oxidative Phosphorylation:
    • 10 NADH ⟶ 30 ATP
    • 2 FADH2 ⟶ 4 ATP
• Overall, one molecule of glucose produces approximately 38 ATPs.

Current Research

• Some details of the electron transport chain are still an active area of research.
• Exact mechanisms of protein complexes involved are not fully understood.
• ATP synthase mechanism involves a rotating axle driven by proton flow.

Significance of ETC

• Main source of ATP in cellular respiration.
• Complements the energy produced in glycolysis and the Krebs cycle.
• Vital in both plant and animal cells for energy production.

Key Terms

• Oxidation: Loss of electrons.
• Reduction: Gain of electrons.
• Proton-motive force: The force generated by the transmembrane proton gradient.
• ATP Synthase: Enzyme that synthesizes ATP utilizing the proton gradient.

Additional Points

• Importance of membrane structure and the impermeability of the cristae to protons.
• Efficiency can be affected by leaks and other potential losses in the system.
• Demonstrates how cellular respiration is a highly efficient process for energy conversion.