Notes on Aerobic Cellular Respiration

Introduction

• Distinction between morning person and not.
• Cells need to perform processes continuously, including active transport.
• ATP (adenosine triphosphate) is the energy currency for cells.

ATP Overview

• ATP is a type of nucleic acid with three phosphates.
• Important for all cells, both prokaryotic and eukaryotic, to produce ATP.
• Focus on aerobic cellular respiration in eukaryotic cells (protists, fungi, animals, plants).
• Mitochondria play a crucial role in aerobic cellular respiration.

Aerobic Cellular Respiration Equation

• Reactants (inputs) on the left, products (outputs) on the right.
• Similarities with photosynthesis:
  • Photosynthesis produces glucose, while cellular respiration breaks it down to make ATP.
  • Example: Germinating bean relies on stored glucose for ATP.

Steps of Aerobic Cellular Respiration

Step 1: Glycolysis

• Occurs in cytoplasm, does not require oxygen (anaerobic).
• Converts glucose to pyruvate.
• Net yield per glucose: 2 pyruvate, 2 ATP, and 2 NADH.
• NADH is a coenzyme important for later ATP production.

Intermediate Step

• Pyruvate transported into mitochondria (mitochondrial matrix).
• Pyruvate oxidized to 2 acetyl CoA; carbon dioxide released; 2 NADH produced.

Step 2: Krebs Cycle (Citric Acid Cycle)

• Takes place in mitochondrial matrix, considered aerobic.
• Acetyl CoA enters the cycle.
• Products: 2 ATP, 6 NADH, and 2 FADH2.
• FADH2 is another coenzyme essential for ATP production.

Step 3: Electron Transport Chain and Chemiosmosis

• Occurs in inner mitochondrial membrane, requires oxygen.
• Electrons from NADH and FADH2 are transferred to protein complexes.
• Proton gradient generated, leading to ATP production via ATP synthase.
• Oxygen acts as the final electron acceptor, forming water (H2O).

ATP Yield Estimates

• Electron transport chain and chemiosmosis yield varies (26-34 ATP/molecule of glucose).
• Total yield from all steps (glycolysis, Krebs cycle, electron transport): 30-38 ATP per glucose molecule.

Alternative Processes

• If oxygen is lacking, cells can undergo fermentation to produce ATP (less efficient).
• Importance of ATP production emphasized, including dangers of inhibitors like cyanide.
• Increased research needed for mitochondrial diseases.

Conclusion

• Importance of questions and curiosity in understanding cellular processes.