Cellular Respiration and the Krebs Cycle

Cellular Respiration Overview

• Involves oxidation-reduction (redox) reactions to harness energy from food.
• Major steps: Glycolysis, Pyruvate Oxidation, Krebs Cycle (Citric Acid Cycle), Electron Transport Chain, Chemiosmosis.

Pyruvate Oxidation

• Pyruvate is oxidized to form Acetyl CoA in the mitochondrion matrix when O2 is available.
• Produces:
  • Acetyl CoA (2-carbon molecule)
  • NADH (energy-rich molecule)
  • CO2 (waste product)

Krebs Cycle (Citric Acid Cycle)

• Occurs in the mitochondrial matrix.
• Converts Acetyl CoA into:
  • 3 NADH
  • 1 FADH2
  • 1 GTP
  • 2 CO2 (waste products)
• Enzyme reactions release energy-rich products used for ATP synthesis.

Energy Production

• Energy-rich molecules:
  • 1 NADH ≈ 2.5 - 3 ATP
  • 1 FADH2 ≈ 1.5 - 2 ATP
• GTP can be converted to ATP by nucleoside-diphosphate kinase.

Role of Coenzymes and Vitamins

• Vitamin B cofactors are required for enzymes in pyruvate oxidation and Krebs cycle.

Importance of Mitochondria

• Mitochondria contain multiple copies of enzymes for efficient energy production via catabolic processes.

Waste Removal

• CO2 produced during pyruvate oxidation and Krebs cycle is exhaled to prevent toxic buildup.

Summary of Learning Outcomes

• Identify redox reactions for energy transfer.
• Recognize the importance of the mitochondrion in ATP production and energy metabolism.
• Understand the process of converting food molecules into usable energy forms (NADH, FADH2, GTP) during cellular respiration.