Lecture Notes on Aerobic Cellular Respiration

Introduction

• Discussion about morning energy levels and comparison to cells.
• Cells perform processes continuously and require energy in the form of ATP (adenosine triphosphate).

ATP Overview

• ATP: a type of nucleic acid with three phosphates; serves as the energy currency for cells.
• ATP must be produced by cells, regardless of type (prokaryote or eukaryote).

Aerobic Cellular Respiration

• Focus on eukaryotic cells, which have membrane-bound organelles like mitochondria.
• The primary goal: to make ATP.
• Equation Overview:
  • Reactants (inputs) on the left side, products (outputs) on the right side.
  • Similar to photosynthesis (e.g., glucose is produced in photosynthesis and consumed in cellular respiration).

Importance of Glucose

• Organisms need glucose to start the cellular respiration process.
• Example: Germinating beans rely on stored glucose for cellular respiration before they can perform photosynthesis.

Steps of Aerobic Cellular Respiration

Step 1: Glycolysis

• Occurs in the cytoplasm and does not require oxygen (anaerobic).
• Converts glucose into pyruvate.
• Net Yield:
  • 2 pyruvate
  • 2 ATP
  • 2 NADH (coenzyme that transfers electrons).

Intermediate Step

• 2 pyruvate transported to mitochondria and converted to 2 acetyl CoA.
• Releases carbon dioxide and produces 2 NADH.

Step 2: Krebs Cycle (Citric Acid Cycle)

• Takes place in the mitochondrial matrix and is aerobic (requires oxygen indirectly).
• Outputs:
  • Carbon dioxide
  • 2 ATP
  • 6 NADH
  • 2 FADH2 (another coenzyme for electron transfer).

Step 3: Electron Transport Chain and Chemiosmosis

• Involves the inner mitochondrial membrane and requires oxygen.
• Electrons from NADH and FADH2 are transferred to protein complexes, generating a proton gradient.
• Protons travel through ATP synthase, which converts ADP to ATP by adding a phosphate.
• Final electron acceptor is oxygen, which forms water (H2O).

ATP Yield

• Variable ATP yield from glucose:
  • Estimates range from 26-34 ATP from the electron transport chain and chemiosmosis alone.
  • Total estimates from glycolysis, Krebs cycle, and electron transport range from 30-38 ATP per glucose molecule.

Fermentation

• Alternative process when oxygen is unavailable; less efficient than aerobic respiration.
• Important for understanding ATP production and mitochondrial diseases.

Conclusion

• Emphasis on the significance of ATP production for cellular function.
• Awareness of poisons like cyanide that can inhibit ATP production, illustrating the critical role of mitochondria.
• Encouragement for continued curiosity and research in cellular biology.