Anaerobic respirationIB MYP Biology: Subtopic test

1. 1
   In a 400 m final in Kingston, Jamaica, an athlete sprints so hard that her muscles cannot be supplied with oxygen as fast as they need it. After she crosses the line she keeps breathing very deeply and quickly for several minutes.

   (a)

   Which substance builds up in the athlete's muscles during the sprint?

   [1 mark]

   • AEthanol
   • BStarch
   • CLactic acid
   • DOxygen

   (b)

   Why does the athlete keep breathing deeply after the race?

   [1 mark]

   • ATo take in extra oxygen to break down the lactic acid
   • BTo make more lactic acid
   • CTo remove ethanol from her blood
   • DTo start anaerobic respiration again

   (c)

   Explain why the athlete's muscle cells respire anaerobically during the sprint.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A baker in Istanbul mixes yeast, flour, sugar and warm water into a dough and leaves it covered in a bowl. After an hour the dough has doubled in size and is full of small holes.

   (a)

   What is the name of anaerobic respiration in yeast?

   [1 mark]

   • APhotosynthesis
   • BDigestion
   • CTranspiration
   • DFermentation

   (b)

   Which word equation represents the anaerobic respiration of yeast?

   [1 mark]

   • Aglucose → lactic acid
   • Bglucose → ethanol + carbon dioxide
   • Cglucose + oxygen → carbon dioxide + water
   • Dcarbon dioxide + water → glucose + oxygen

   (c)

   Explain why the dough rises.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A student investigates whether the amount of sugar affects how fast yeast ferments. She makes four mixtures, each with 5 g of yeast in 50 cm³ of sugar solution, with sugar concentrations of 0%, 2%, 5% and 10%. She covers each mixture with a thin layer of oil and passes the gas it gives off through a tube into water, counting the bubbles during 5 minutes. She records 0 bubbles for 0%, 14 bubbles for 2%, 31 bubbles for 5% and 52 bubbles for 10%.

   (a)

   State a hypothesis for this investigation with a scientific reason, and name one control variable.

   [3 marks]

   (b)

   Describe the trend in the results and evaluate the method.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   In Brazil, sugar cane juice is fermented by yeast in large closed tanks to make ethanol, which is blended with petrol and used as a car fuel. The industry employs many people but needs large areas of farmland. Yeast cells and human muscle cells can both release energy without using oxygen.

   (a)

   Compare aerobic respiration with anaerobic respiration in human muscle cells, and explain what is meant by oxygen debt.

   [6 marks]

   (b)

   Discuss and evaluate whether Brazil should continue to produce ethanol fuel by fermenting sugar cane.

   [6 marks]

   Total for question 4: 12 marks

End of questions