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(a) (i) Prepare the space below to record your colour observations and the number using the scale shown in Fig. 1.2.
(a) (ii) Complete the following by using one of the words 'more' or 'less'.
You may use each word once or more than once.
U is ................. concentrated than 0.8% (P1).
U is ................. concentrated than 1.6% (P2).
Use your results to estimate the concentration of albumin in U.
(a) (iii) State which solution P1 or P2 you will dilute to prepare further concentrations.
Explain the reason for your decision.
(a) (iv) Complete Fig. 1.4 on page 6 to show how you will dilute the solution you decided on in (iii) to prepare a serial dilution.
You should use the two beakers shown in Fig. 1.4 and add as many extra beakers as you need to prepare a serial dilution.
(v) Prepare the space below to record your colour observations and the number using the scale shown in Fig. 1.2 (page 4).
(vi) Using these additional results from (v) state a more accurate estimate of the concentration of albumin in U.
(vii) Replicating the investigation would increase the confidence in the accuracy of your estimate.
Describe one other modification which would increase the confidence in your estimate.
(b) (i) Plot a chart of the data in Table 1.1.
[Table_1]
(ii) Suggest one reason for the pattern of the results shown in the chart.
(iii) The concentration of albumin in a person's blood may be measured to identify health problems. One of the reasons for a health problem is that blood albumin has a low solubility in water.
Suggest one health problem which may be caused by an albumin concentration of 5.6–6.0 g per 100 cm3.
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L1 is a slide of a stained transverse section through a leaf. This plant species grows widely including Europe, Africa and Asia.
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.
(a) (i) Draw a large plan diagram of the part of the specimen on L1 indicated by the shaded sector in Fig. 2.1.
[Image_1: Fig. 2.1]
On your diagram:
• ignore the trichomes (either attached or loose)
• use one ruled label line and label to show the palisade layer. [5]
(ii) Select one whole trichome:
• made up of at least three cells
• attached to at least one epidermal cell.
Make a large drawing of this trichome attached to at least one epidermal cell.
Use one ruled label line and label to show one nucleus. [4]
(b) Fig. 2.2 is a photomicrograph of a stained transverse section through another species of leaf.
[Image_2: Fig. 2.2]
(i) Prepare the space below so that it is suitable for you to show the observable differences between the specimens shown on L1 and Fig. 2.2.
Record your observations in the space you have prepared. [4]
(ii) Calculate the actual length of the fold shown by line X, using the scale bar.
You may lose marks if you do not show your working or if you do not use appropriate units.
actual length ................................................... [4]
(iii) Describe how you would obtain the mean maximum actual length of the folds in the specimen shown in Fig. 2.2.
........................................................................................................................
........................................................................................................................
........................................................................................................................
........................................................................................................................
...............................................................................................[2]
(iv) Suggest one observable feature, other than trichomes, shown by both the specimen on L1 and the specimen in Fig. 2.2 which supports the conclusion that these plants grow in dry conditions.
Explain how this feature may help the plants grow in dry conditions by preventing water loss.
feature ..........................................................
explanation .........................................................
.................................................................[1]
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590
576
