cellular respiration 2

• Pathways of aerobic respiration

  • Glycolysis
  • Citric acid Cycle
  • Electron transport chain
• Glycolysis

  Breakdown of glucose to pyruvate
• Glycolysis

  1. ATP required for phosphorylation of glucose and intermediates (2 ATP)

  2. Generation of more ATP during energy pay-off stage (4 ATP)

  3. Net gain of 2 ATP
• Dehydrogenase enzymes

  Remove hydrogen ions and electrons and pass them to the coenzyme NAD, forming NADH
• Dehydrogenase enzymes occur in both glycolysis and the citric acid cycle
• Electron transport chain

  Hydrogen ions and electrons from NADH are passed to the electron transport chain on the inner mitochondrial membrane
• Aerobic conditions

  1. Pyruvate is converted into an acetyl group that combines with coenzyme A forming acetyl coenzyme A

  2. NADH and carbon dioxide are also formed
• Citric cycle

  1. Acetyl group from acetyl coenzyme A combines with oxaloacetate to form citrate

  2. Citrate is gradually converted back into oxaloacetate

  3. Generation of ATP and release of carbon dioxide
• Locations of respiration stages

  • Glycolysis – Cytoplasm
  • Citric acid cycle – Matrix of the mitochondria
  • Electron Transport chain – within the inner mitochondrial membrane
• Electron transport chain

  • Series of carrier proteins attached to the inner mitochondrial membrane
  • Electrons are passed along releasing energy
  • Energy allows hydrogen ions to be pumped across the inner mitochondrial membrane
  • Flow of ions back through ATP synthase results in ATP production
  • Hydrogen ions and electrons combine with oxygen to form water
• In the absence of oxygen, fermentation takes place in the cytoplasm
• Fermentation results in much less ATP being produced than in aerobic respiration
• Fermentation products

  • Lactate (in animal cells)
  • Ethanol and carbon dioxide (in plants and yeast)
• ATP

  Used to transfer energy to cellular processes which require energy