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You are provided with solutions S1, S2, S3, S4 and S5 which represent extracts from different tissues of a plant, including the xylem.
You are required to identify which biological molecule may be present in each of the plant extracts.
Four of the solutions contain one type of biological molecule, which could be:
• glucose
• protein
• starch
• sucrose.
Each solution contains one type of biological molecule, but the same type of biological molecule may be present in more than one of S1, S2, S3, S4 and S5.
For example, glucose may be present in S1 AND S2.
The solution from the xylem does not contain any of these biological molecules.
You are provided with:
[Table_1]
Proceed as follows:
(a) (i) As you carry out each test to identify the presence or absence of the biological molecule in S1, S2, S3, S4 and S5, complete the following:
Decide which biological molecule to identify in the first test.
First test: Test for ...............................
Describe how you used the reagents to carry out this test.
.................................................................................................................................
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Carry out the first test and record your observations.
[Table_2]
Use these observations to complete the sentence.
Solution(s) ............................... contain(s) the biological molecule ............................... .
Decide which biological molecule to identify in the second test.
Second test: Test for ...............................
Describe how you used the reagents to carry out this test.
.................................................................................................................................
.................................................................................................................................
.................................................................................................................................
.................................................................................................................................
Carry out the second test and record your observations.
[Table_3]
Use these observations to complete the sentence.
Solution(s) ............................... contain(s) the biological molecule ............................... .
Decide which biological molecule to identify in the third test.
Third test: Test for ...............................
Describe how you used the reagents to carry out this test.
.................................................................................................................................
.................................................................................................................................
.................................................................................................................................
Carry out the third test and record your observations.
[Table_4]
Use these observations to complete the sentence.
Solution(s) ............................... contain(s) the biological molecule ............................... .
Decide which biological molecule to identify in the fourth test.
Fourth test: Test for ...............................
Describe how you used the reagents to carry out this test.
.................................................................................................................................
.................................................................................................................................
.................................................................................................................................
Carry out the fourth test and record your observations.
[Table_5]
Use these observations to complete the sentence.
Solution(s) ............................... contain(s) the biological molecule ............................... .
From these observations, the remaining solution ............................... contains ............................... .
[15]
(ii) Identify which of the solutions S1, S2, S3, S4 and S5 is most likely to be the plant extract from the phloem.
.................................................................................................................................[1]
(b) Describe how the student would find the concentration of reducing sugars in each plant extract.
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.................................................................................................................................[3]
564
556
588
Fig. 2.1 shows a photomicrograph of a transverse section through part of a plant stem showing the eyepiece graticule scale as seen using a microscope.
Fig. 2.1
An eyepiece graticule scale can be used to measure the layers of tissues and to help draw a plan diagram with the correct shape and proportions of the tissues, without needing to calibrate the eyepiece graticule scale.
(a) (i) The length of the vascular bundle (from K to R) in Fig. 2.1 was measured using the eyepiece graticule scale and recorded in Table 2.1.
[Table_1]
Complete Table 2.1 by finding the thickness of each of the different layers, L, M, N, and P using the line between K and R and the eyepiece graticule scale.
(ii) Complete the plan diagram of the vascular bundle to show the proportion and shape of each of the tissues. Use the values in Table 2.1 to help you.
[3]
(iii) Using Fig. 2.2, count the total number of 1 cm by 1 cm squares occupied by the vascular bundle and count the total number of 1 cm by 1 cm squares occupied by the xylem.
Count any `half square` or `more than half` as one square.
State the ratio of the area occupied by the vascular bundle to that of the xylem.
You will lose marks if you do not show all the steps in finding the ratio, including indicating counted squares on Fig. 2.2.
ratio ...................................................[2]
Some scientists investigated the rate of transpiration during part of a day.
The results are shown in Table 2.2.
[Table_2]
(b) (i) Plot a graph of the data shown in Table 2.2. [4]
(ii) From your graph, state the rate of transpiration at 14.30 hours.
Show on your graph where you obtained the rate of transpiration.
..................................................[1]
J1 is a slide of a transverse section through another plant stem. This plant grows mainly in Europe and Asia.
This stem shows a layer of stained cells close to the epidermis and just beneath these cells is another tissue close to the vascular bundles.
(c) Make a large drawing of one group of three whole adjacent (touching) cells
• from the layer of stained cells close to the epidermis, as observed on the specimen J1.
Make a large drawing of one group of three whole adjacent (touching) cells
• from the cells between the layer of stained cells and the vascular bundles, as observed on the specimen J1.
The drawings should show any difference in size (linear magnification) observed between each group of cells.
layer of stained cells
cells between the layer of stained cells and the vascular bundles
[4]
Fig. 2.3 shows a photomicrograph of a transverse section through part of a different plant stem.
Fig. 2.3
(d) Prepare the space below so that it is suitable for you to record the observable differences between the specimen on slide J1 and in Fig. 2.3 to include:
• the vascular tissue
• at least two other tissues.
[5]
548
547
541
