AS & A Level Biology - 9700 Paper 3 2014 Summer Zone 5

During the summer, certain plants translocate sucrose from the leaves to the roots to be stored as starch. In the spring, this starch is hydrolysed to produce glucose which will provide energy for new growth. You are provided with three samples, S1, S2 and S3 from plant root extracts, removed at different times of the year:
• the middle of winter, when there was no plant growth
• the beginning of spring, when plant growth begins
• the middle of spring, during active growth.
(a) (i) These extracts were tested for starch. Predict the colour that was observed and complete the table.

time of year extract was taken	predicted colour
middle of winter
beginning of spring
middle of spring

[1]
You are required to:
• compare the concentrations of starch in the samples S1, S2 and S3
• identify the time of year when each extract was taken.
You are provided with:

labelled	hazard	volume/cm3
S1	none	20
S2	none	20
S3	none	20

(ii) State the reagent you will use to compare the concentrations of starch and describe how you will standardise the starch test for each sample.
reagent .................................................................................................................
description .........................................................................................................
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Proceed as follows:
• Carry out the starch test as described in (a)(ii).
(iii) Prepare the space below and record your observations. [3]
(iv) Complete the table to match the samples S1, S2 and S3 with the time of year that each extract was taken from the root.

time of year extract was taken	sample
middle of winter
beginning of spring
middle of spring

[1]
You are required to estimate the concentration of glucose in S3 using G1 and G2.
You are provided with:

labelled	hazard	percentage concentration of glucose	volume/cm3
G1	none	0.1	20
G2	none	1.0	20

Proceed as follows:
1. Carry out tests to compare the concentration of glucose in S3, G1 and G2 using the apparatus and reagents provided.
You will need to record the time taken for the first appearance of a colour change at the top of the mixture of the sample with the selected reagent(s). If no colour change occurs after 5 minutes, stop the experiment and record 'more than 300'.
(v) Prepare the space below and record your results. [3]
(vi) Use the results you obtained to estimate the concentration of glucose found in S3.
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.............................................................................................................................. [1]
(vii) Suggest how you would modify this investigation to obtain a more accurate estimate of the glucose concentration in S3.
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(viii) A systematic error occurs when apparatus with scales are used, since the scales may be slightly different.
For example, when measuring the same line, two rulers may give different lengths. However, as long as the same ruler is used for all the measurements, the trend is not affected because the error is consistent.
State one piece of apparatus used in this investigation that may have a systematic error. Suggest whether this affected your results and give a reason for your answer.
apparatus .............................................................................................................
effect and reason .................................................................................................
.............................................................................................................................. [1]
(b) Certain plants translocate sucrose from the leaves to the roots to be stored as sucrose rather than as starch. These roots can be harvested and kept in storage until they are sold. However, water loss during storage reduces their value.
A scientist investigated how water loss from these roots was affected by the time in storage. Constant temperature and humidity were maintained during storage. Ten roots were weighed at five day intervals. The mean percentage change in water content was calculated. It was found that all the roots had lost water.
The results are shown in Table 1.1.

time in storage/days	mean percentage change in water content
5	−6.25
10	−11.00
15	−15.50
20	−17.25
25	−17.50

(i) Plot a graph of the data in Table 1.1.
[4]
(ii) Ten roots were stored for 5 days, and another ten roots were stored for 20 days. Pieces of root from the sample at 5 days and from the sample at 20 days were removed, weighed and soaked in dilute sucrose solution for 24 hours. The pieces were then reweighed.
State which sample would have the highest percentage gain in mass after soaking in the dilute sucrose solution.
Explain your answer using your knowledge of water potential.
sample ................................................................................................................
explanation ........................................................................................................
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(a) Draw large plan diagrams of two different types of blood vessel shown in K1 and K2.

On your diagram, use ruled label lines and labels to describe (annotate) one observable difference in the layer lining the inside of each vessel.

(b) Make a large drawing of five whole white blood cells in the area shown on Fig. 2.1.

Use ruled label lines and labels to one cell you have drawn to identify three cell structures that can also be found in plant cells.

[Image_1: Fig. 2.1]

(c) (i) To diagnose cancer of the white blood cells a sample of blood is taken and a total blood cell count is carried out on the sample.

State one difference, other than size, between the blood shown in Fig. 2.1 and that in Fig. 2.2 that indicates that the person is suffering from cancer which affects the white blood cells.

Explain the reason for this difference.

difference ...............................................................

explanation ............................................................

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[Image_2: Fig. 2.2]

(c) (ii) A student measured the longest length of five red blood cells P, Q, R, S and T shown in Fig. 2.3 and found the mean actual length of the red blood cells.

Use the magnification to calculate the mean actual length, in 𝜇m, of the red blood cells using the five labelled red blood cells in Fig. 2.3.

You may lose marks if you do not show your working or if you do not use appropriate units.

mean actual length ............................𝜇m

[Image_3: Fig. 2.3]

(d) Prepare the space below so that it is suitable for you to record the observable differences between the red blood cells in Fig. 2.2 and Fig. 2.3.

Record your observations in the space you have prepared.