Lecture Notes: Aerobic Cellular Respiration in Eukaryotic Cells

Introduction

• Importance of ATP (adenosine triphosphate) as energy currency in cells.
  • Composed of three phosphates.
  • Required by all cells (prokaryotic and eukaryotic).
• Cells constantly perform active transport and other processes needing ATP.

ATP Production

• Aerobic Cellular Respiration
  • Focuses on eukaryotic cells (with membrane-bound organelles like nucleus and mitochondria).
  • Main goal: Produce ATP.

Overall Equation

• Reactants (inputs) on left; products (outputs) on the right.
• Similar to photosynthesis but not opposites.
• Glucose is broken down to produce ATP.

Initial Concept

• Plants perform both photosynthesis (to make glucose) and cellular respiration (to break it down).
• Non-photosynthetic organisms (e.g., humans, amoebas) must obtain glucose from food.

Steps of Aerobic Cellular Respiration

Step 1: Glycolysis

• Location: Cytoplasm
• Nature: Anaerobic (does not require oxygen)
• Process:
  • Converts glucose to pyruvate.
  • Requires a little ATP to start.
• Net Yield: 2 Pyruvate, 2 ATP, 2 NADH.
• NADH: Coenzyme that transfers electrons.

Intermediate Step

• Transport of pyruvate into mitochondria.
• Conversion to 2 acetyl CoA.
• Release of carbon dioxide and production of 2 NADH.

Step 2: Krebs Cycle (Citric Acid Cycle)

• Location: Mitochondrial matrix
• Nature: Aerobic (indirectly requires oxygen)
• Process:
  • Acetyl CoA enters the cycle.
  • Produces 2 ATP, 6 NADH, 2 FADH2.
• FADH2: Coenzyme aiding in electron transfer.
• Release of carbon dioxide.

Step 3: Electron Transport Chain and Chemiosmosis

• Location: Inner mitochondrial membrane
• Nature: Aerobic (requires oxygen)
• Process:
  • Electrons transferred from NADH and FADH2 to protein complexes.
  • Proton gradient generated across the membrane.
  • Protons travel through ATP synthase, producing ATP.
• Oxygen as final electron acceptor, forming water.
• Produces significantly more ATP than other steps.

ATP Yield

• Estimates range: 26-34 ATP from electron transport chain and chemiosmosis alone.
• Total range per glucose: 30-38 ATP including all steps.
• Variation due to different variables (e.g., proton gradient).

Alternative Pathways

• Fermentation
  • Used when oxygen is not available.
  • Less efficient in ATP production.

Importance and Implications

• ATP production is critical; inhibitors like cyanide can be deadly.
• Mitochondrial diseases are a research focus.
• Encouragement to stay curious and continue research.

Conclusion

• Understanding of ATP production in cells is vital.
• Continued research and curiosity are encouraged.