5.2 Respiration

• Why is respiration important?

  ● Respiration produces ATP (to release energy)

  ● For active transport, protein synthesis

  
• Summarise the stages of aerobic respiration

  Aerobic respiration

  1. Glycolysis - cytoplasm (anaerobic)

  2. Link reaction - mitochondrial matrix

  3. Krebs cycle - mitochondrial matrix

  4. Oxidative phosphorylation - inner mitochondrial membrane
• Summarise the stages of anaerobic respiration

  Anaerobic respiration

  1. Glycolysis - cytoplasm

  2. NAD regeneration - cytoplasm
• Describe the process of glycolysis

  1. Glucose phosphorylated to glucose phosphate ○ Using inorganic phosphates from 2 ATP
  2. Hydrolysed to 2 x triose phosphate
  3. Oxidised to 2 pyruvate

  ○ 2 NAD reduced

  ○ 4 ATP regenerated (net gain of 2)

  
• Explain what happens after glycolysis if respiration is anaerobic

  1. Pyruvate converted to lactate (animals & some bacteria) or ethanol (plants & yeast)
  2. Oxidising reduced NAD → NAD regenerated
  3. So glycolysis can continue (which needs NAD) allowing continued production of ATP

  
• Suggest why anaerobic respiration produces less ATP per molecule of glucose than aerobic respiration

  ● Only glycolysis involved which produces little ATP (2 molecules)

  ● No oxidative phosphorylation which forms majority of ATP (around 34 molecules
• What happens after glycolysis if respiration is aerobic?

  Pyruvate is actively transported into the mitochondrial matrix
• Describe the link reaction

  1. Pyruvate oxidised (and decarboxylated) to acetate

  ○ CO2 produced

  ○ Reduced NAD produced (picks up H)

  2. Acetate combines with coenzyme A, forming Acetyl

  Coenzyme A Products per glucose molecule: 2 x Acetyl Coenzyme A, 2 X CO2 and 2 X reduced NAD

  
• Describe the Krebs cycle

  1. Acetyl coenzyme A (2C) reacts with a 4C molecule

  ○ Releasing coenzyme A

  ○ Producing a 6C molecule that enters the Krebs cycle

  2. In a series of oxidation-reduction reactions, the 4C molecule is regenerated and:

  ○ 2x CO2 lost

  ○ Coenzymes NAD & FAD reduced

  ○ Substrate level phosphorylation (direct transfer of Pi from intermediate compound to ADP) → ATP produced Products per glucose molecule: 6 x reduced NAD, 2 x reduced FAD, 2 x ATP and 4 x CO2