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(a) (i) Record the volume of H needed to reach the end-point.
volume of H ........................................................... [1]
Yeast cells release carbon dioxide from some of their metabolic reactions.
A student investigated the release of carbon dioxide from a yeast cell suspension, using the apparatus shown in Fig. 1.2.
You are required to investigate the release of carbon dioxide bubbles during 10 minutes using apparatus set up as in Fig. 1.2.
You will move the delivery tube to different test-tubes containing C, at different times during 10 minutes.
(ii) Decide the length of time you will leave the delivery tube in each test-tube containing C. State the length of time.
time ...................................................................................................................... [1]
(iii) State one significant source of error that may occur when the delivery tube is moved from one test-tube to the next.
Describe how you will reduce this error.
source of error .......................................................................................................
description ............................................................................................................
.................................................................................................................................
................................................................................................................................. [2]
(iv) Prepare the space below and record your results.
................................................................................................................................. ................................................................................................................................. ................................................................................................................................. ................................................................................................................................. [5]
(v) Identify one significant source of error in measuring the dependent variable in this investigation.
................................................................................................................................. ................................................................................................................................. ................................................................................................................................. ................................................................................................................................. [1]
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 ..............................................................................................................
reason ....................................................................................................................
................................................................................................................................. [1]
(b) Increasing concentrations of carbon dioxide in the atmosphere have been recorded by scientists for over one hundred years and can be used to predict future increases.
Scientists have studied the effect of carbon dioxide on the leaf area of two different types of plants, R and T, after 60 days.
A large sample of each type of plant was grown in air containing one of the following concentrations of carbon dioxide:
- 280 μmol mol^{-1} (the concentration measured in the atmosphere around the year 1900)
- 380 μmol mol^{-1} (the concentration measured in the atmosphere now)
- 719 μmol mol^{-1} (the concentration which is predicted in the atmosphere for the year 2100).
All other variables were standardised.
On day 60 the mean leaf area per plant was calculated.
The results are shown in Table 1.1.
Table 1.1
| concentration of CO_{2} / μmol mol^{-1} | mean leaf area / cm^{2} plant^{-1} ×10^{3} | |
|---|---|---|
| plant R | plant T | |
| 280 | 1.00 | 1.50 |
| 380 | 2.55 | 3.35 |
| 719 | 4.20 | 3.90 |
(i) Complete Fig. 1.4 by plotting a chart of the data in Table 1.1.
concentration of carbon dioxide/ μmol mol^{-1}
(plot chart on Fig. 1.4) [3]
(ii) Describe the trends shown on the chart for R and T.
................................................................................................................................. ................................................................................................................................. ................................................................................................................................. ................................................................................................................................. [2]
(iii) Suggest how the differences in the leaf area in plant R may affect transport in this plant.
................................................................................................................................. ................................................................................................................................. ................................................................................................................................. ................................................................................................................................. ................................................................................................................................. ................................................................................................................................. [2]
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(a) (i) Prepare the space below and record your observations by:
• making drawings of three cells from each of the slides in the boxes provided
• annotating your drawings to describe the effect of methylene blue, M on the cells.
[Image of S1]
[Image of S2]
[Image of S3]
(a) (ii) Use your observations to identify the temperature that was used to heat each of the suspensions S1, S2 and S3. Complete the table.
[Table: 'suspension', 'temperature /\u00b0C']
(a) (iii) Explain how you identified the yeast cells that had been heated at 100\u00b0C.
(a) (iv) A student was provided with a suspension of yeast cells which had been heated at a temperature between 45\u00b0C and 80\u00b0C. Describe how you could modify this investigation to provide quantitative measurements that can be used to estimate this temperature.
(b) (i) Make a large drawing of the whole cells shown in the area on Fig. 2.1. On your drawing, use a label line and label to show one observable feature of these cells which identify them as being similar to animal cells.
[Image: Fig. 2.1 - photomicrograph of yeast cells]
(b) (ii) Use the magnification to calculate the mean maximum actual length, in \u03bcm, of yeast cells, X1, X2, X3, X4 and X5. You may lose marks if you do not show your working or if you do not use the appropriate units.
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