cellular respiration

• Site of cellular respiration in eukaryotes is mitochondria
• Cellular Respiration: Three Stages
• Pyruvate Oxidation


  1. Takes place in mitochondria

  2. Pyruvate oxidized to acetyl groups (2C)

  3. Electrons removed are accepted by NAD+

  4. CO2 is produced
• Three phases of cellular respiration

  • Glycolysis
  • Pyruvate oxidation and the citric acid cycle
  • Oxidative phosphorylation
• Citric Acid Cycle

  1. Acetyl groups completely oxidized to CO2

  2. Electrons removed in oxidations accepted by NAD+ or FAD

  3. Substrate-level phosphory
• Glycolysis

  • Universal metabolic process
  • Does not require O2
  • Occurs in cytosol of all cells requiring soluble enzymes
  • Glucose (6 carbons) is oxidized into two molecules of pyruvate (3 carbons each)
• Protein complexes pump H+ and cycle between reduced and oxidized states in the Electron Transport Chain
• Pyruvate Oxidation and Citric Acid Cycle
• Each acetyl group oxidized in the Citric Acid Cycle produces

  1. 2 CO2

  2. 1 ATP

  3. 3 NADH

  4. 1 FADH2
• Electrons are removed in oxidations and accepted by NAD+ or FAD
• Some energy is used by complexes to pump protons (H+) across the inner mitochondrial membrane
• Components of the Electron Transport Chain

  • 4 protein complexes
  • 2 smaller shuttle carriers
• ATP Synthase is a molecular motor
• ATP synthase catalyzes ATP synthesis using energy from the H+ gradient across the membrane in Oxidative Phosphorylation and Chemiosmosis
• Substrate-level phosphorylation

  Produces ATP
• Acetyl groups completely oxidized to CO2 in the Citric Acid Cycle
• Electrons pass through carriers stepwise in the Electron Transport Chain
• Electrons pass from NADH2 and FADH2 to O2 in the Respiratory Electron Transport Chain
• Electrons are depleted of energy and delivered to oxygen as the final electron acceptor
• Major protein complexes in the Electron Transport Chain

  • I
  • III
  • IV
• ATP synthase is embedded in the inner mitochondrial membrane with the electron transfer system
• Electron transport and chemiosmotic generation of ATP are separate and distinct processes