Lecture on Cellular Respiration: Oxidation and Reduction

Introduction

• Key Concepts:
  • Oxidation and reduction are fundamental to generating ATP in cellular respiration.
  • These reactions involve the transfer of electrons between molecules.

Oxidation and Reduction

• Definitions:
  • Oxidation: Loss of electrons by a molecule.
  • Reduction: Gain of electrons by a molecule.
• Oxidation and reduction always occur together, termed redox reactions.
• Mnemonic: "Oil Rig" - Oxidation is Loss of electrons, Reduction is Gain of electrons.

Visualizing Oxidation and Reduction

• Example with Molecules A and B:
  • Molecule A loses electrons (oxidized).
  • Molecule B gains electrons (reduced).
• Analogy: Like playing catch with a ball (electrons).

Role of NAD in Cellular Respiration

• NAD (Nicotinamide Adenine Dinucleotide):
  • Acts as an electron carrier.
  • Exists in two forms: NAD+ (oxidized) and NADH (reduced).
  • NAD+ picks up electrons and becomes NADH.
  • Made from niacin (Vitamin B3).

Process in Cellular Respiration

• Glucose Breakdown:
  • Electrons are stripped from glucose.
  • Electrons are transferred to NAD+, forming NADH.
• Electron Transport Chain:
  • NADH donates electrons, becomes oxidized back to NAD+.
  • Electrons used to generate ATP.

Detailed Mechanism

• Electron Transfer:
  • Focus on electrons from hydrogen atoms (each hydrogen = 1 proton + 1 electron).
• Cycle:
  • NAD+ accepts electrons (reduced to NADH).
  • NADH donates electrons in the electron transport chain (oxidized back to NAD+).

Practice Questions

1. Question 1: During glycolysis

   • G3P is oxidized to 1,3-bisphosphoglycerate.
   • NAD+ is reduced to NADH.
   • Enzyme Hint: Dehydrogenases remove hydrogens (indicative of oxidation).
   • H+ ions are released during NAD+ reduction to NADH.

2. Question 2: Final step of cellular respiration

   • Oxygen is reduced to form water.
   • Oxygen gains electrons and hydrogen ions to become water.

Conclusion

• Understanding redox reactions (oxidation and reduction) is crucial for comprehending cellular respiration.
• Key takeaway: Oxidation is the loss of electrons and reduction is the gain of electrons.