Respiration

• Describe how acetylcoenzyme A is formed in the link reaction

  Pyruvate undergoes decarboxylation(loose carbon) and oxidation(loose hydrogen) and this forms acetate. Addition of coenzyme A to acetate to form acetylcoenzyme A.
• Oxaloacetate is the first substrate to bind with the enzyme citrate synthase. This induces a change in the enzyme, which enables the acetylcoenzyme A to bind. Explain how oxaloacetate enables the acetylcoenzyme A to then bind to the enzyme.

  Change in active site, so substrate complementary
• Another substrate in the Krebs Cycle is called succinyl coenzyme A. This substance has a very similar shape to acetylcoenzyme A. Suggest how the production of succinyl coenzyme A could control the rate of the reaction catalysed by citrate synthase.

  Is competitive inhibitor so prevent enzyme-substrate forming
• In muscles, pyruvate is converted to lactate during anaerobic respiration. Explain why converting pyruvate to lactate allows the continued production of ATP during anaerobic respiration.

  Regeneration of NAD and NAD used in glycolysis 
• In muscles, some of the lactate is converted back to pyruvate when they are well supplied with oxygen. Suggest one advantage of this. 


  Reduced muscle fatigue
• Respiration produces more ATP per molecule of glucose in the presence of oxygen than it does when oxygen is absent. Explain why

  Oxygen is terminal electron acceptor. Oxidative phosphorylation provides most ATP
• Describe the process of glycolysis 


  Phosphorylation of glucose using ATP. Oxidation of triose phosphate to pyruvate. Net gain of ATP and NAD reduced.
• Malonate inhibits a reaction in the Krebs Cycle. Explain why malonate would decrease the uptake of oxygen in a respiring cell.

  No reduced NAD and oxygen is the final electron acceptor
• In muscles, pyruvate is converted to lactate during prolonged exercise. Explain why converting pyruvate to lactate allows the continued production of ATP by anaerobic respiration

  Regenerates NAD so glycolysis continues
• Explain why a log scale is used to record the number of cells

  There's a large range
• Many yeast cells die during the death phase

  Decrease in pH
• Describe the advantage of the Bohr Effect during intense exercise

  Increases dissociation of oxygen for aerobic respiration at the muscles