Anaerobic respiration and respiratory substratesAQA A-Level Biology: Mind map

Exam questions on Anaerobic respiration and respiratory substrates

1. A brewery grows yeast in a sealed fermentation vessel containing glucose solution. Once the dissolved oxygen has been used up, the yeast respires only anaerobically: the liquid slowly gains ethanol and carbon dioxide bubbles out through an airlock.
   Explain why the yeast would run out of ATP if it could not convert ethanal to ethanol.2 marks
2. During a 400 m sprint, the leg muscle cells of an athlete use oxygen faster than the blood can deliver it. The concentration of lactate in her blood rises sharply during the race.
   Explain how the formation of lactate allows the muscle cells to go on making some ATP.2 marks
3. A student investigates the effect of temperature on the rate of anaerobic respiration of a yeast culture. For each temperature she mixes 10 cm³ of yeast suspension with 10 cm³ of glucose solution, covers it with a layer of oil to exclude oxygen, and collects the carbon dioxide released in an inverted measuring cylinder over water for 5.0 minutes. The tubes are kept in water baths at 20, 30, 40 and 50 °C. At 40 °C the volume collected was greatest; at 50 °C it was less than at 40 °C.
   At 30 °C the student collected 7.5 cm³ of carbon dioxide in 5.0 minutes from yeast of dry mass 0.50 g. Calculate the rate of carbon dioxide production in cm³ min⁻¹ g⁻¹ of yeast.3 marks