Cellular Respiration Lecture Notes

Introduction to Cellular Respiration

• Adenosine Triphosphate (ATP):
  • Primary energy molecule used by cells.
  • Often compared to money as cellular currency.
  • Energy is stored in the bonds between the second and third phosphate.
  • Hydrolysis of ATP:
    • Breaks ATP into ADP, a single phosphate, and energy with the help of water.
    • Energy released powers cellular processes.

ATP Creation

• Purpose of Cellular Respiration:
  • To produce ATP.
  • Most ATP produced in the mitochondria, the "powerhouse" of the cell.
• Process Overview:
  • Breakdown of glucose from food to produce ATP.
  • Main stages: Glycolysis, Krebs Cycle, and Electron Transport Chain.

Glycolysis

• Location: Cytoplasm of the cell.
• Process:
  • Glucose is broken down by ATP, NAD, and enzymes.
  • Initial breakdown requires ATP, but ultimately produces more ATP.
• Steps:
  • Breakdown of glucose into PGAL (phosphoglyceraldehyde).
  • Enzymes add phosphates, converting PGAL to intermediate molecules.
  • NADH is produced as a hydrogen carrier to the mitochondria.
• ATP Production:
  • 4 ATP molecules created (Net gain of 2 ATPs after subtracting the 2 ATPs used).
• End Products: Two pyruvate molecules, used in the Krebs Cycle.

Pathways after Glycolysis

• Aerobic Conditions:
  • Follow Krebs Cycle and Electron Transport Chain.
• Anaerobic Conditions:
  • Lead to fermentation (not covered in this lecture).

Krebs Cycle (Citric Acid Cycle)

• Location: Mitochondrial Matrix.
• Process:
  • Pyruvate broken down to acetic acid, then acetyl-CoA.
  • Acetyl-CoA converted to citric acid by bonding with a 4-carbon molecule.
  • Citric acid broken down to a 5-carbon, then a 4-carbon molecule, producing NADH, ATP, and CO2.
  • Rearrangement of 4-carbon molecule completes the cycle, which repeats.
• Main Products: NADH and FADH2 (important for the Electron Transport Chain).

Electron Transport Chain

• Location: Inner mitochondrial membrane.
• Components: Protein complexes in the membrane.
• Process:
  • NADH and FADH2 broken down, releasing electrons.
  • Electrons drive the transport of hydrogen ions out of the matrix.
  • Hydrogen ions diffuse back through ATP synthase.
  • ATP synthase synthesizes ATP from ADP and phosphate.
  • Oxygen bonds with hydrogens and electrons to form water.
• ATP Yield: Up to 34 ATP molecules.

Conclusion

• Overall Purpose: Efficient production of ATP.
• By-products: Water and carbon dioxide.
• Importance: Essential for energy-dependent cellular functions.

Pause and review questions provided at the end for self-assessment and understanding.