Anaerobic respiration and comparing processesIB MYP Sciences: Mind map

Exam questions on Anaerobic respiration and comparing processes

1. A sprinter in Doha runs a 400 m race at top speed. By the final 100 m her leg muscles burn and feel heavy. After she crosses the line she stands bent over, still breathing very hard for several minutes.
   Explain why the sprinter's leg muscles respire anaerobically during the race.2 marks
2. A bakery in Istanbul makes bread by mixing flour, water, sugar and yeast into a dough. The dough is left in a warm place for an hour. It swells to about twice its size, and when it is baked the bread has a light texture full of tiny holes.
   Explain why the dough swells while it is left in a warm place.2 marks
3. A student in Cape Town investigates yeast. She mixes the same mass of yeast with 100 cm³ of glucose solution in four flasks. Each flask is kept at a different constant temperature in a water bath: 20 °C, 30 °C, 40 °C and 60 °C. Each flask is sealed with a bung and a delivery tube that leads into water, and she counts the bubbles of gas leaving the tube during 5 minutes. She counts 12 bubbles at 20 °C, 28 bubbles at 30 °C, 45 bubbles at 40 °C and no bubbles at 60 °C.
   State a testable hypothesis for this investigation and give a scientific reason for it.3 marks