1. 1
   A sprinter is being monitored by a sports scientist during a 100 m race and the minutes immediately afterwards, to study how the athlete's muscles release energy.

   (a)

   Which products are released by aerobic respiration?

   [1 mark]

   • ALactic acid
   • BEthanol
   • CCarbon dioxide and water
   • DGlucose

   (b)

   In which cell structure does most aerobic respiration take place?

   [1 mark]

   • ANucleus
   • BMitochondria
   • CRibosomes
   • DCell membrane

   (c)

   Explain why, during the sprint, the athlete's leg muscles respire anaerobically and produce lactic acid.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A bakery uses yeast in its bread dough, leaving it in a warm place to rise before baking.

   (a)

   In yeast, anaerobic respiration produces which two substances?

   [1 mark]

   • ALactic acid and water
   • BGlucose and starch
   • COxygen and water
   • DEthanol and carbon dioxide

   (b)

   Which type of respiration requires oxygen?

   [1 mark]

   • AAnaerobic respiration
   • BAerobic respiration
   • CFermentation in yeast
   • DAnaerobic respiration in muscle

   (c)

   Explain why the bread dough rises while the yeast respires anaerobically in the warm, sealed conditions.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A sports scientist is investigating how quickly an athlete's breathing rate returns to normal after a period of intense exercise on a treadmill.

   (a)

   Describe what is meant by oxygen debt and explain why it must be repaid after exercise.

   [3 marks]

   (b)

   Explain the differences between aerobic and anaerobic respiration in terms of oxygen requirement, products formed, and the amount of energy released.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A biology teacher is explaining to a class why the body's cells constantly need to release energy, both during rest and during exercise, and how this differs between organisms.

   (a)

   Explain the process of aerobic respiration, including its word equation, balanced chemical equation and the cell structure where it occurs, and describe how the energy released is used by the body.

   [6 marks]

   (b)

   Compare aerobic respiration with anaerobic respiration in animals and in plants/yeast, including the word equation and the conditions under which each type occurs.

   [6 marks]

   Total for question 4: 12 marks

End of questions