In aerobic respiration, organisms take in oxygen and release carbon dioxide.
A group of students used the apparatus in Fig. 2.1 to investigate how quickly germinating seeds respired.
The carbon dioxide given off by the germinating seeds was removed by the soda lime. As oxygen was consumed, the gas volume inside the apparatus decreased, so the drop of coloured liquid travelled along the capillary tube towards the seeds.
The students returned the drop of coloured liquid in the capillary tube to the start of the scale (0 mm) by opening the three-way tap and using the syringe to gently force air into the apparatus. The tap was then closed.
This was the starting position of the drop of coloured liquid. Its position on the scale was noted during the next four minutes. The distance moved by the drop of coloured liquid shows the respiration rate of the seeds.
The students’ results are given in Table 2.1.
(a(i))[4]
Using the grid, construct a line graph from the data in Table 2.1. The axis end values are already shown on the grid. Draw a straight best-fit line to join the points.
(a(ii))[2]
From your graph, predict the position of the drop of coloured liquid at 5 minutes. Show how you obtained your answer on the graph.
(a(iii))[2]
Using the value at 4 minutes in Table 2.1, calculate the rate at which the drop of coloured liquid moves because the seeds are respiring.
(b)[6]
Plan an investigation to find the effect of temperature on the respiration rate of germinating seeds. Use the apparatus in Fig. 2.1 in your plan.
Worked solution & mark scheme
This 14-mark question has a full step-by-step worked solution and mark scheme. One marking point: “Axes labelled in full” …