7.2 Respiration

• The four stages of aerobic respiration are Glycolysis, Link Reaction, Krebs cycle, and Oxidation Phosphorylation.
• Glycolysis takes place in the cytoplasm of the cell.
• The Link reaction takes place in the matrix of the mitochondria.
• Krebs cycle takes place in the matrix of the mitochondria.
• Oxidative Phosphorylation takes place in the inner mitochondrial membrane.
• What is the difference between aerobic and anaerobic respiration?


  Aerobic respiration requires oxygen and produces more ATP, while anaerobic respiration does not require oxygen and produces less ATP.
• What is oxidation?


  Loss of electrons, gain of oxygen, or loss of hydrogen.
• What is reduction?


  Gain of electrons, loss of oxygen, or gain of hydrogen.
• Why is ATP such a useful store of energy in cells?


  ATP releases energy in small, manageable amounts. It is an immediate energy source. It is also reformed.
• ATP phosphorylates other compounds.
• ATP makes phosphorylated substances more reactive.
• Mitochondria is the site of aerobic respiration.
• The compensation point is when the rate of photosynthesis is equal to the rate of respiration.
• Glucose is not suitable as an immediate energy source in cells.
• Substrate-level phosphorylation is where ATP is generated directly through respiration (glycolysis and Krebs cycle).
• Oxidative phosphorylation is when ATP is generated from chemical energy released when a hydrogen carrier or coenzyme has been reduced.
• How is glucose converted to glucose phosphate?


  Glucose is phosphorylated by ATP to form phosphorylated glucose and ADP + Pi.
• How many ATP molecules are created during glycolysis?


  Four - but two are used to phosphorylate glucose, so the net gain is two.
• What is the net output of glucose?

  2 Pyruvate

  2 ATP

  2 Reduced NAD
• In aerobic respiration, what happens to pyruvate?


  It enters the mitochondria to join the Link reaction.
• What is the name of the reaction that uses the pyruvate from glycolysis?


  Link reaction.
• In order to ensure there is a constant supply of pyruvate inside the mitochondria, cells cannot rely on the presence of a concentration gradient of pyruvate, so what transport is occurring?


  Active Transport.
• The Link reaction takes place in the matrix of the mitochondria.
• In the Link reaction, pyruvate is oxidised to form reduced NAD and decarboxylated to form CO2.
• The Link reaction happens twice per molecule of glucose.
• One Krebs cycle forms:

  3 Reduced NAD

  1 Reduced FAD

  1 ATP

  2 CO2
• What happens to the pyruvate in the Link reaction?


  It is oxidised to form reduced NAD and decarboxylated to form CO2.
• Suggest why pyruvate can enter the mitochondria and glucose cannot.


  There is a specific carrier protein that can transfer pyruvate across the membrane by active transport, but there are no specific carrier proteins for glucose.