Lecture Notes: Aerobic Cellular Respiration in Eukaryotic Cells

Introduction

• ATP (Adenosine Triphosphate): Energy currency for cells.
  • Type of nucleic acid with three phosphates.
  • Crucial for cell processes like active transport.

Importance of ATP

• All cells need ATP, regardless of being prokaryote or eukaryote.
• Different methods for ATP synthesis:
  • Aerobic Cellular Respiration (focus of the lecture)

Aerobic Cellular Respiration in Eukaryotic Cells

• Eukaryotic cells: Have nucleus and mitochondria (membrane-bound organelles).
  • Includes protists, fungi, animals, and plants.
  • Mitochondria play a significant role in ATP production.

Overall Equation for Aerobic Cellular Respiration

• Reactants (inputs) ➡️ Products (outputs)
  • Equation opposite to photosynthesis.
  • Photosynthetic organisms: Make glucose (photosynthesis) & break it down for ATP (cellular respiration).
  • Non-photosynthetic organisms (humans, amoebas): Obtain glucose from food.

Steps of Aerobic Cellular Respiration

Step #1: Glycolysis

• Location: Cytoplasm
• Nature: Anaerobic (no oxygen required)
• Process:
  • Glucose ➡️ Pyruvate
  • Requires some ATP to start.
  • Yields: 2 Pyruvate + 2 ATP + 2 NADH
  • NADH: Coenzyme, helps transfer electrons.

Intermediate Step

• Transport: Pyruvate ➡️ Mitochondrial Matrix
• Process: Pyruvate oxidation (pyruvate ➡️ Acetyl CoA)
  • Produces: CO2 + 2 NADH

Step #2: Krebs Cycle (Citric Acid Cycle)

• Location: Mitochondrial Matrix
• Nature: Aerobic process
• Process: Acetyl CoA enters the cycle
  • Produces: 2 ATP + 6 NADH + 2 FADH2 + CO2
  • FADH2: Another coenzyme, transfers electrons.

Step #3: Electron Transport Chain & Chemiosmosis

• Location: Inner Mitochondrial Membrane
• Nature: Aerobic step (requires oxygen)
• Process:
  • Electrons from NADH and FADH2 transferred to protein complexes and carriers
  • Generates a proton gradient (protons pumped to intermembrane space)
  • Protons (H+) travel back through ATP Synthase enzyme
    • ATP Synthase: Adds a phosphate to ADP ➡️ forms ATP
  • Oxygen is the final electron acceptor ➡️ Forms water (H2O)
• Yield: Varying estimates, 26-34 ATP for this step, total 30-38 ATP per glucose molecule including all steps.

Alternatives to Aerobic Respiration

• Fermentation: Used when no oxygen is available
  • Less efficient than aerobic respiration.

Additional Notes

• Importance of ATP production.
• Cyanide effect: Blocks electron transport chain ➡️ blocks ATP production.
• Ongoing research on mitochondrial diseases.

Conclusion

• Critical importance of ATP and cellular respiration.
• Encouragement to stay curious and keep asking questions.