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(a) (i) Show clearly on the diagrams below, using the key, how you would expect to see the drop or small volume of P move if:
P is less concentrated than the sucrose solution
P is the same concentration the sucrose solution
P is more concentrated than the sucrose solution
Key:
a drop or small volume of P moves up
a drop or small volume of P moves down
a drop or small volume of P remains at same level
(iii) Complete the following by using one of the words ‘more’ or ‘less’.
You may use each word once or more than once.
P is .................. concentrated than 0.1 mol·dm⁻³ (S1).
P is .................. concentrated than 1.0 mol·dm⁻³ (S2).
Use your results to estimate the concentration of sucrose in P.
estimate of concentration of sucrose in P ..................................................
(iv) State which solution, S1 or S2, you will dilute to prepare further concentrations.
Use your results to explain the reason for your decision.
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(v) Prepare the space below to show:
• the concentration of each sucrose solution
• the volumes of sucrose solution
• the volumes of W.
(vii) Using these additional results from (vi) state a more accurate estimate of the concentration of sucrose in P than in (iii).
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(viii) Describe how you would modify this procedure to investigate the concentration of sucrose in P, using Benedict’s solution.
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576
564
589
Plants translocate sap through phloem sieve tubes. Scientists discovered that aphids feed by pushing their stylet into a single phloem sieve tube as shown in Fig. 2.1. By using stylets it is possible for scientists to collect the sap from a single phloem sieve tube.
Fig. 2.1
Scientists have investigated the different rates of flow of sap in the stylets of aphids of different ages from hatching, H, up to the adult, M.
The results are shown in Table 2.1.
[Table_1]
(a) (i) Circle the two anomalous results in Table 2.1. [1]
(ii) Complete the table by calculating the missing mean value. [1]
(iii) Plot a chart of the data in Table 2.1. [4]
(iv) Describe the relationship between the age of the aphid and the rate of flow of sap. [1]
(v) Suggest two reasons which might explain the relationship described in (iv). [2]
(b) K1 is a slide of a stained transverse section through a plant stem. This plant species grows widely including Europe, Asia and North America.
You are not expected to be familiar with this specimen.
To help draw a plan diagram with the correct shape and proportions of the tissues, an eyepiece graticule can be used to measure the layers of tissues, without the need to calibrate the eyepiece graticule scale.
(i) Draw a large plan diagram of the part of the specimen on K1 indicated by the shaded sector in Fig. 2.2.
Use one ruled label line and label to show the pith. [5]
(ii) Observe the tissue between the xylem and the hollow centre of the specimen.
Select one group of three cells with:
• one cell containing cell structures
• two cells which touch each other and also touch the cell which contains cell structures.
Make a large drawing of this group of three cells.
Use one ruled label line and label D to show one of the cell structures. [5]
(c) Calculate the actual length of the structure R to T, using the magnification, giving your answer in μm.
You may lose marks if you do not show your working or if you do not use appropriate units.
actual length .......................................................... μm [4]
560
586
535
