1. 1
   A sprinter runs a 200 metre race, requiring an intense burst of energy from her leg muscles.

   (a)

   Which molecule, produced during respiration, directly provides usable energy for muscle contraction?

   [1 mark]

   • AATP
   • BGlucose
   • COxygen
   • DDNA

   (b)

   During the intense final seconds of the sprint, the sprinter's muscles cannot get enough oxygen from the blood to meet their energy demands. Which type of respiration mainly occurs in her muscle cells at this point?

   [1 mark]

   • AAerobic respiration
   • BAnaerobic respiration
   • CPhotosynthesis
   • DOsmosis

   (c)

   State the word equation for anaerobic respiration occurring in the sprinter's muscle cells, and give one way in which anaerobic respiration differs from aerobic respiration.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A grain merchant stores a sealed silo of damp wheat seeds that have begun to germinate. Over several days, a thermometer inside the silo shows the temperature rising.

   (a)

   Which gas would you expect to increase in concentration inside the sealed silo as a result of the seeds respiring?

   [1 mark]

   • ANitrogen
   • BOxygen
   • CCarbon dioxide
   • DHydrogen

   (b)

   Besides carbon dioxide, which other substance is produced by the aerobic respiration taking place in the germinating seeds?

   [1 mark]

   • AEthanol
   • BStarch
   • CLactic acid
   • DWater

   (c)

   Explain why the temperature inside the silo rises as the seeds germinate.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   An 18th-century scientist places a small live mammal in a sealed glass jar containing limewater, alongside a thermometer, to investigate the gases and heat produced by a living organism over one hour.

   (a)

   Describe how the scientist could show, using this apparatus, that the mammal releases carbon dioxide and produces heat while respiring.

   [3 marks]

   (b)

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

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A sports scientist is assessing an athlete's muscle performance during repeated sprint efforts in training.

   (a)

   Explain, in detail, the process of aerobic respiration, including the word equation, where in the cell it mainly occurs, and how the ATP produced is used by muscle cells during exercise.

   [6 marks]

   (b)

   After finishing a race, the athlete continues to breathe heavily and rapidly for several minutes, even though she has stopped running. Explain why this happens, referring to the build-up of lactic acid during the race and the concept of oxygen debt.

   [6 marks]

   Total for question 4: 12 marks

End of questions