1.7

• Adenosine Triphosphate (ATP)


  A high energy-carrying molecule used in cells because it can release energy very quickly
• Adenosine Diphosphate (ADP)


  A low energy molecule
• Electron transport chain


  A series of carrier proteins attached to the inner mitochondrial membrane
• Mitochondria


  Organelle found in cell cytoplasm where aerobic respiration takes place
• Phosphorylation


  A biochemical process that involves the addition of phosphate to an organic compound
• Pi


  Inorganic phosphate molecule
• Substrate


  A substance on which enzymes act
• Conversion of ATP to ADP +Pi

  1. Once ATP has released energy, it becomes ADP

  2. Energy is released from ATP when the end phosphate is removed

  3. ADP can be converted into ATP by adding a phosphate. This requires energy
• Glycolysis


  1. Breakdown of glucose to pyruvate in the cytoplasm

  2. This process does NOT require oxygen

  3. Involves the production of several intermediate molecules

  4. Energy-investment stage: Phosphorylation of glucose and intermediates requires ATP

  5. Energy pay-off stage: More ATP molecules are then generated than were used
• Coenzyme (NAD)


  Involved in glycolysis
• If oxygen is available (aerobic conditions)

  Pyruvate molecules progress into the citric acid cycle
• If oxygen is not available


  Pyruvate undergoes fermentation in the cytoplasm of the cell
• Dehydrogenase enzymes


  • Remove hydrogen ions and electrons and pass them to the coenzyme NAD, forming NADH
  • This occurs in BOTH glycolysis and the citric acid cycle
• Citric acid cycle


  1. Occurs in the matrix of the mitochondria

  2. In aerobic conditions, pyruvate is broken down to an acetyl group that combines with coenzyme A forming acetyl coenzyme A

  3. The acetyl group from acetyl coenzyme A combines with oxaloacetate to form citrate

  4. Citrate is gradually converted back into oxaloacetate which results in the generation of ATP and release of carbon dioxide
• NADH


  Reduced coenzyme that passes hydrogen ions and electrons to the electron transport chain
• Electron transport chain


  1. The last stage of the respiration pathway that produces the most ATP molecules

  2. NADH releases the hydrogen ions and electrons into the transport chain

  3. Electrons are passed along the chain releasing energy

  4. This energy allows hydrogen ions to be pumped across the inner mitochondrial membrane

  5. The flow of these ions back through the membrane protein ATP synthase results in the production of ATP (38 ATP molecules produced from one glucose molecule)

  6. Oxygen is the final hydrogen ion and electron acceptor, combining with them to form water
• ATP


  Used to transfer energy to cellular processes which require energy, such as DNA replication, active transport, muscle contraction, and protein synthesis