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(a) State the hazard with the greatest level of risk when using the solutions in Table 1.1. State the level of risk of using the solutions: low or medium or high.
hazard ...........................................................
level of risk .......................................................
(b) (i) State the volume of pH indicator solution you will use to observe the colour change clearly and describe how you will standardise the volume of the pH indicator solutions to carry out step 9.
volume ............................... cm3
description .......................................................
..................................................................
(ii) Prepare the space below and record all your observations.
(iii) Fig. 1.1 shows the position of pH 7 on a scale. Using your results in (b)(ii) complete Fig. 1.1 to show:
- the positions of pH 3, pH 4 and pH 6 on the scale
- the positions of W, S1 and S2 on the scale
[Image_Fig_1.1]
(c) Like red cabbage, beetroot cells also contain anthocyanins. A student investigated the effect of temperature on the cell surface membranes of beetroot. Beetroot was cut into 1 cm3 cubes. One cube of beetroot was put into each of five test-tubes containing water which had been heated to 25°C or 30°C or 35°C or 45°C or 50°C. All other variables were standardised. The cubes were removed after 15 minutes. The absorbance of light by the coloured liquid left in the test-tubes was measured using a colorimeter.
The absorbance of light by pure water is 0.000 arbitrary units.
The results of the student's investigation are shown in Table 1.2.
[Table_1.2]
You are required to use a sharp pencil for graphs.
(i) Plot a graph of the data shown in Table 1.2.
(ii) Use your graph to estimate the absorbance of light at 40°C. Show on your graph how you estimated the absorbance of light.
absorbance ....................................................
(iii) Explain the effect of temperature on the permeability of cell surface membranes in beetroot.
...................................................................
...................................................................
...................................................................
The student decided to investigate the effect of alcohol on the cell surface membranes of beetroot cubes at 20°C.
(iv) Describe how the temperature will be standardised in this investigation.
...................................................................
(v) Describe how the independent variable will be investigated.
...................................................................
...................................................................
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L1 is a slide of a stained transverse section through a plant stem.
You are not expected to be familiar with this specimen.
You are required to use a sharp pencil for drawings.
(a) (i) Draw a large plan diagram of half of the stem to show the observable features.
Use one ruled label line and label to identify the xylem. [5]
(ii) Annotate your diagram to describe one difference between the cells in the centre (pith) and the cells in the outer layer (epidermis). [1]
(iii) Select one group of four cells from the pith. Each cell of the group must touch two of the other cells.
Make a large drawing of this group of four cells.
Use one ruled label line and label to identify a cell wall. [5]
(b) Fig. 2.1 and Fig. 2.2 are photomicrographs of transverse sections (TS) of leaves from the same plant.
TS of leaf grown in sunlight
Fig. 2.1
TS of leaf grown in shade
Fig. 2.2
(i) Calculate the actual thickness of the leaf grown in sunlight as shown by line Y on Fig. 2.1.
You may lose marks if you do not show your working or if you do not use appropriate units.
actual length ..........................................................µm [3]
(ii) Prepare the space below so that it is suitable for you to record observable differences between Fig. 2.1 and Fig. 2.2.
Do not include difference in thickness of the leaves.
Record your observations in the space you have prepared. [4]
(iii) A student observed a different plant of the same species shown in Fig. 2.1. The student determined the ratio of the thickness of a leaf grown in sunlight to the thickness of a leaf grown in shade as 120:60.
However, a ratio may be simplified to the smallest possible whole number on each side.
In this example, both sides of the ratio 120:60 are divisible by 60, so the simplest ratio for the thickness of leaves measured by the student is 2:1.
The actual thickness of the leaf grown in shade in Fig. 2.2 is 70µm.
Determine the simplest ratio of the thickness of the leaf grown in sunlight in Fig. 2.1 compared to the thickness of the leaf grown in shade in Fig. 2.2.
ratio .......................................................... [1]
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