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Enzyme, E hydrolyses (breaks down) one substrate (biological molecule) present in one of the solutions S1, S2 or S3.
You are required to:
• identify which biological molecule may be present in each solution, S1, S2 and S3
• identify which of the biological molecules in the solutions S1, S2 and S3 can be hydrolysed by E.
The solutions contain one type of biological molecule which may be:
• glucose
• 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 and S3.
For example glucose may be present in S1 AND S2.
You are provided with:
| labelled | hazard | volume /cm3 |
|---|---|---|
| S1, S2 and S3 | none | 25 |
| E | irritant | 15 |
Read to the end of page 6 before proceeding.
Proceed as follows:
(a) As you carry out each test to identify the presence or absence of the biological molecule in S1, S2 and S3, 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.
..................................................................................................................
..................................................................................................................
Carry out the first test and record your observations.
| solutions tested | observations of colour |
|---|---|
| ........................ | ........................ |
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.
| solutions tested | observations of colour |
|---|---|
| ........................ | ........................ |
Use these observations to complete the sentence.
Solution(s) ..................... contain(s) the biological molecule ..................... .
Decide which test you will use to check the identity of the third biological molecule.
Third test: Test for .....................
Describe how you used the reagents to carry out this test.
..................................................................................................................
..................................................................................................................
Carry out the third test and record your observation.
| solution tested | observation of colour |
|---|---|
| ........................ | ........................ |
Use this observation to complete one of the following sentences.
Solution(s) ..................... contain(s) the biological molecule ..................... .
OR
Solution ..................... does not contain any of these biological molecules, glucose, starch or sucrose.
Enzyme, E hydrolyses (breaks down) one biological molecule (substrate) present in one of the solutions S1, S2 or S3.
(b) (i) State which of the biological molecules, glucose, starch or sucrose cannot be hydrolysed by the enzyme, E.
..................................................................................................................
[1]
You are required to identify which of the other two biological molecules is hydrolysed by the enzyme, E using the procedure shown in Fig. 1.1 on each solution.
(ii) Prepare the space below to record:
• the biological molecule tested for
• the observations.
(iii) From your observations, state which of the solutions (S1, S2, S3) is hydrolysed by the enzyme, E. Explain the reason for your answer.
solution ...........
reason ..................................................................................................................
..................................................................................................................
[1]
(c) Describe how you would modify this procedure to investigate the effect of temperature on the enzyme, E.
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[3]
501
527
521
(a) (i) The length of the vascular bundle (from J to R) in Fig. 2.1 was measured using the eyepiece graticule scale and recorded in Table 2.1.
Table 2.1
| layer | L | M | N | P | length from J to R |
|---|---|---|---|---|---|
| number of eyepiece graticule scale divisions | 20 |
Complete Table 2.1 by finding the thickness of each of the different layers L, M, N and P, labelled in Fig. 2.1, using the line between J and R and the eyepiece graticule scale. [2]
(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 1cm by 1cm squares occupied by the vascular bundle and count the total number of 1cm by 1cm 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]
(b) Draw a large plan diagram of a sector of the specimen on K1 to show:
• the epidermis
• three small vascular bundles beneath the epidermis
• one large vascular bundle nearer to the centre
• other observable features. [3]
(c) Select observable features shown on the specimen on K1 which are different from or not observable in Fig. 2.1.
Prepare the space below so that it is suitable for you to record each feature and describe how each feature is different from Fig. 2.1. [4]
(d) (i) Plot a graph of the data shown in Table 2.2.
Table 2.2
| time of day /hours | flow rate in xylem /mg min−1 |
|---|---|
| 00.00 | 0.140 |
| 06.00 | 0.105 |
| 09.00 | 0.220 |
| 17.00 | 0.455 |
| 22.00 | 0.200 |
[4]
(ii) Use the data to describe the trend in the flow rate in the xylem between 10.00 and 17.00 hours. [2]
592
507
542
