Respiration

12 Four people do exactly the same physical exercise. The graph shows their breathing rate in breaths per minute before, during and after the exercise. One person is a professional athlete. Which line shows the results for the professional athlete? 60 50 40 30 20 10 0 breathing rate / breaths per minute time / min before exercise after exercise during exercise A B C D 0 5 10 15 20 25

© UCLES 2025 5090/12/O/N/25 [Turn over 15 The apparatus shown is used to investigate the volume of gas produced by yeast during anaerobic respiration. water mixture of yeast and glucose in water thin layer of oil measuring cylinder Why is the yeast mixture covered with the thin layer of oil in this investigation? A to provide energy for the yeast B to prevent oxygen in the air from reaching the yeast C to prevent heat loss from the mixture D to prevent the yeast mixture from drying out 8

16 The equation shows aerobic respiration. X + 6O2  Y + 6CO2 + energy What do X and Y represent? X Y A 6H2O C6H12O6 B C6H12O6 6H2O C C12H22O11 11H2O D C6H12O6 H2O

© UCLES 2025 5090/12/O/N/25 [Turn over 23 Which term can be used to describe the release of oxygen from plants? A breathing B excretion C respiration D transpiration 10

5090/22/O/N/25 © UCLES 2025 [Turn over 250 cm 3 from metabolism 200 cm 3 in sweat 700 cm 3 in evaporation of water from lungs 1500 cm 3 in urine 750 cm 3 from foods 1500 cm 3 from drinks Fig. 2.1 (i) Calculate the percentage of average daily water intake that is lost in sweat from an adult human. Space for working. ...................................................... % [2] (ii) The percentage of water lost in sweat is not always the same. Explain why. ........................................................................................................................................... ..