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1 (a) (i) Complete Fig. 1.2 to show how you will make three further concentrations of milk, M.
[3]
(ii) Prepare the space below and record your observations and the number using the scale opposite.
[5]
(iii) Complete the diagram below to show the position of each of the concentrations of M. Write the letter U to show where it fits in the series of concentrations.
50% ................. 5% ................. ................. 0%
The protein concentration of the 50% milk, M was 18 g 100 cm^{-3}.
Complete the following statement.
The protein concentration of the unknown milk sample, U, is between ................. g 100 cm^{-3} and ................. g 100 cm^{-3}.
[2]
(iv) Suggest how you would modify this investigation to obtain a more accurate estimate of the protein concentration in milk sample U.
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[3]
2 (b) (i) Plot a graph of the data shown in Table 1.1. [Table_1]
[4]
(ii) Describe and explain the trend in the results.
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[3]
(iii) Fig. 1.4a and Fig. 1.4b show the start and finish times for the student’s second investigation. Use the information from Fig. 1.4a and Fig. 1.4b to calculate the percentage error of the time taken.
Fig. 1.4a Fig. 1.4b
You may lose marks if you do not show your working or if you do not use appropriate units.
percentage error ..........................................................
[2]
513
574
582
K1 is a stained transverse section through part of an organ from a mammal.
Put the slide onto the microscope and move the slide to find the edge of the transverse section of the organ including the darkly stained layer.
Select a part of the section which clearly shows the edge and the darkly stained layer.
(a) Draw a large plan diagram which shows only the layers of the section visible without moving the slide to another field of view.
Use the letter D, with a label line, to show the position of the most darkly stained layer.
[5]
Fig. 2.1 is a photomicrograph of part of K1. The nuclei have been stained.
(b) (i) Make a large drawing of all the whole nuclei shown within the area indicated on Fig. 2.1.
Label one nucleolus.
[4]
(ii) Use the magnification to calculate the actual length of the line L in µm.
You may lose marks if you do not show your working or if you do not use appropriate units.
......................................................... µm [3]
Fig. 2.2 and Fig. 2.3 are photomicrographs of transverse sections through the same organ as K1 from different mammals.
(c) (i) Prepare the space below so that it is suitable for you to record three observable differences between the specimens in Fig. 2.2 and Fig. 2.3.
Record your observations in the space you have prepared.
[5]
(ii) State one observable feature of Fig. 2.2 which supports the conclusion that this is part of an organ that may absorb molecules.
Suggest how this feature may increase the rate of absorption.
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[1]
584
569
530
