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You are provided with five solutions S1, S2, S3, S4 and S5.
These solutions contain starch or protein or reducing sugar in varying concentrations or any two of these or none of them.
Carry out tests, using only the reagents provided, to identify the contents of each of the solutions. Use your results to decide whether the concentration of each of the substances you identify is high or low.
You are required to identify two of the solutions, S1 to S5, that could be mixed together to feed a young mammal.
The mixture needs to contain
- a high concentration of starch,
- a high concentration of protein and
- a low concentration of reducing sugar.
The mixture must be made up from equal volumes of only two of the solutions, S1 to S5.
You will need to consider carefully how you will carry out the tests so that you can determine the relative concentrations of the three substances.
(a) (i) Complete the table below to show how you will carry out the tests on each solution.
[4]
(ii) Prepare the space below and record your observations of the tests on all the solutions.
[6]
(iii) Use your observations to state the two solutions that should be mixed in equal volumes to provide the correct mixture to feed the young mammal.
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[1]
A student investigated the time taken for the complete digestion of starch by an enzyme found in the saliva of 25 individuals of a species of mammal.
A sample of saliva was collected from each individual and mixed with 5 cm3 of 1% starch suspension. Samples of the mixture were tested for the presence of starch.
The student recorded the time taken for the complete digestion of starch.
The investigation was repeated with the same individuals on the following day.
The results of the student’s investigation are shown in Table 1.1.
(b) (i) Plot these data shown in Table 1.1.
[4]
(ii) Describe the patterns in the results.
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[3]
(iii) Suggest a reason for the difference between the results for day 1 and day 2.
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[1]
(iv) Suggest how you might control the variables in this investigation to compare a different species of mammal with the mammal studied.
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[3]
561
580
565
J1 is a slide of a stained transverse section of a leaf.
You are not expected to have studied this leaf.
(a) (i) Draw a large low-power plan diagram of the midrib of the leaf as shown in the shaded area in Fig. 2.1.
Label the upper surface and one vascular bundle.
[5]
J1 is a leaf from a plant which grows in dry, sunny habitats.
(ii) Describe one visible adaptation of this leaf and suggest a possible advantage to the plant.
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(iii) Using the eyepiece graticule and slide J1, find the ratio of the thickness of the midrib compared to the thickness of the lamina.
The position of the midrib and the lamina are shown in Fig. 2.2.
You must show your measurements and all the steps in your calculation.
[3]
(b) (i) Make a large, high-power drawing of a group of three cells from the upper epidermis and the cells touching them.
Label a cell wall.
[4]
(ii) Prepare the space below so that it is suitable for you to record the observable differences between the upper and lower epidermis of the leaf.
Record your observations in the space you have prepared.
[4]
579
531
600
