Lecture on FADH2 and Electron Transport Chain

Key Concepts

• FADH2 Formation

  • Conversion of succinate to fumarate involves FAD and FADH2.
  • Complex II facilitates this conversion.
  • Electrons from the reaction are transferred to coenzyme Q.
  • FADH2 is embedded in Complex II.

• Electron Transport Chain (ETC)

  • FADH2 donates electrons directly to Complex II, bypassing Complex I.
  • Electrons flow to coenzyme Q, then Complex III, cytochrome C, and finally to oxygen.

• ATP Production

  • NADH can produce more ATP than FADH2 because it powers three pumps in the ETC.
  • NADH pumps a total of 10 protons across the membrane (4 at Complex I, 4 at Complex III, and 2 at Complex IV).
  • FADH2 bypasses Complex I, resulting in fewer protons (6) being pumped and less ATP production.
  • 4 protons are required to synthesize one ATP; thus, FADH2 effectively produces 1.5 ATP, rounded to 2.

ATP Yield per Glucose

• Theoretical Yield
  • From NADH: 30 ATP
  • From FADH2: 4 ATP
  • Total: 38 ATP (ideal conditions)

Homework and Exercises

• Assignment: Pages 15, 16, and 17 from the packet.

  • Focus on cellular respiration math.
  • Complete six problems assuming full oxidation of 12 glucose molecules.

• Specific Questions:

  1. Total ATP from glycolysis and the citric acid cycle (not considering electron transport).
  2. Total FAD reduction to FADH2.
  3. Total carbon dioxide from the prep reaction.
  4. ATP yield from NADH in the prep reaction and the Krebs cycle.
  5. Net ATP from glycolysis, prep reaction, Krebs cycle, and oxidative phosphorylation.
  6. Total protons pumped during oxidative phosphorylation.

• Hints for Homework:

  • Break problems into proportions (e.g., ATP per glucose in glycolysis).
  • Consider relationships like glucose to pyruvate to acetyl-CoA.

Upcoming Topics

• Review answers and discuss math on Tuesday.
• Beta oxidation and continuation of Chapter 3.
• Possible start of Chapter 4.