AS & A Level Biology - 9700 Paper 3 2018 Summer Zone 3

1. Set up a water-bath and heat to boiling ready for step 7 and step 13. You will need to make simple (proportional) dilutions of the sucrose solution S5 and prepare the concentrations of sucrose solution: • 4.0% sucrose concentration, to be labelled S4 • 3.0% sucrose concentration, to be labelled S3 • 2.0% sucrose concentration, to be labelled S2 You will need to prepare 10 cm$^3$ of each concentration. (a) (i) Complete Table 1.2 to show how you will prepare these concentrations. [Table 1.2] S5 | 10.0 | 0 | 5.0 S4 | S3 | S2 |

2. Prepare the concentrations of sucrose as stated in Table 1.2 in the beakers provided. The sucrose concentration can be estimated by using the non-reducing sugar test. To test for the presence of a non-reducing sugar, any non-reducing sugars must be hydrolysed (broken down) into the reducing sugars. For example, boiling sucrose with dilute hydrochloric acid hydrolyses sucrose into glucose and fructose, which are both reducing sugars. The Benedict’s test can then be used to show the presence of these reducing sugars. 3. Put 2 cm$^3$ of S5 into a labelled test-tube. 4. Put 2 cm$^3$ of H into the same test-tube. 5. Shake the test-tube gently to mix the contents. 6. Repeat step 3 to step 5 for S4, S3, S2 and U. 7. Put all the test-tubes into the boiling water-bath (set up in step 1). Leave them for 2 minutes. 8. After 2 minutes, remove the test-tubes from the water-bath and put them in the test-tube rack. 9. Leave the test-tubes to cool for a further 3 minutes. You will need the boiling water-bath for step 13. 10. After 3 minutes put a small amount of A into each test-tube. The mixture will fizz and rise up the test-tube. Repeat until there is no more fizzing. This neutralises the acid so that the Benedict’s solution can work. Note: there may be some of A left in the bottom of some of the test-tubes. This will not affect the results. 11. Put 3 cm$^3$ of Benedict’s solution into the test-tube containing S5. 12. Shake the test-tube gently to mix the contents. 13. Put this test-tube in the boiling water-bath. Start timing. 14. Measure the time taken to the first appearance of a colour change in the test-tube. If there is no colour change after 120 seconds, stop timing and record as ‘more than 120’. 15. Record the result in (a)(ii). 16. Remove the test-tube from the water-bath and put it in the test-tube rack. 17. Repeat step 11 to step 16 with each of the other concentrations of sucrose solution. 18. Repeat step 11 to step 14 with the sample from U. 19. Record the result for U in (a)(iii). (ii) Record your results for the known concentrations of sucrose solution in an appropriate table.

(iii) State the time taken for the appearance of the first colour change for U. ........................................................ Complete Fig. 1.1 to show an estimate of the percentage concentration of sucrose solution in the sample U, using the letter U. [Fig. 1.1 with percentage scale] (iv) The concentration of sucrose in U can also be estimated from a graph of your results. Draw a graph using the results you recorded in (a)(ii) on the grid in Fig. 1.2. The axes have been labelled for you. Use a sharp pencil for drawing graphs. [Fig. 1.2 graph grid] (v) Use your graph and the time stated in (a)(iii) to estimate the percentage concentration of sucrose in U. Show on the graph how you determined your answer. percentage concentration of sucrose solution in U ........................................................ [1] (vi) Identify one significant source of error in this investigation. ........................................................ [1] (vii) A student carried out the same procedure to estimate the percentage concentration of sucrose solution in a different fruit extract. The estimate for the percentage concentration of sucrose solution was found to be below 2.0%. Apart from drawing a graph, suggest how the student could improve this procedure to obtain a more accurate estimate of the percentage concentration of sucrose solution in this fruit extract. ........................................................ [3] (b) Maturing fruits contain many types of sugar. The proportions of these different sugars vary according to the type of fruit. A scientist carried out some tests to determine the mass of each type of sugar found in one type of fruit. The total mass of the fruit was 55g. The results are shown in Table 1.3. [Table 1.3 with sugar types and masses] (i) Calculate the percentage of the fruit that is made up of sugars. Show all the steps in your working. percentage = ........................................................ [3] (ii) Draw a bar chart of the data shown in Table 1.3 on the grid in Fig. 1.3. Each bar should be separated for each type of sugar. Use a sharp pencil for drawing bar charts. [Fig. 1.3 bar chart grid] (iii) Name one source of the sucrose in the plant and the process used for loading the sucrose into the phloem tissue. source ........................................................ process ........................................................ [2]

1. Set up a water-bath and heat to boiling ready for step 7 and step 13. You will need to make simple (proportional) dilutions of the sucrose solution S5 and prepare the concentrations of sucrose solution: • 4.0% sucrose concentration, to be labelled S4 • 3.0% sucrose concentration, to be labelled S3 • 2.0% sucrose concentration, to be labelled S2 You will need to prepare 10 cm$^3$ of each concentration. (a) (i) Complete Table 1.2 to show how you will prepare these concentrations. [Table 1.2] S5 | 10.0 | 0 | 5.0 S4 | S3 | S2 |

2. Prepare the concentrations of sucrose as stated in Table 1.2 in the beakers provided. The sucrose concentration can be estimated by using the non-reducing sugar test. To test for the presence of a non-reducing sugar, any non-reducing sugars must be hydrolysed (broken down) into the reducing sugars. For example, boiling sucrose with dilute hydrochloric acid hydrolyses sucrose into glucose and fructose, which are both reducing sugars. The Benedict’s test can then be used to show the presence of these reducing sugars. 3. Put 2 cm$^3$ of S5 into a labelled test-tube. 4. Put 2 cm$^3$ of H into the same test-tube. 5. Shake the test-tube gently to mix the contents. 6. Repeat step 3 to step 5 for S4, S3, S2 and U. 7. Put all the test-tubes into the boiling water-bath (set up in step 1). Leave them for 2 minutes. 8. After 2 minutes, remove the test-tubes from the water-bath and put them in the test-tube rack. 9. Leave the test-tubes to cool for a further 3 minutes. You will need the boiling water-bath for step 13. 10. After 3 minutes put a small amount of A into each test-tube. The mixture will fizz and rise up the test-tube. Repeat until there is no more fizzing. This neutralises the acid so that the Benedict’s solution can work. Note: there may be some of A left in the bottom of some of the test-tubes. This will not affect the results. 11. Put 3 cm$^3$ of Benedict’s solution into the test-tube containing S5. 12. Shake the test-tube gently to mix the contents. 13. Put this test-tube in the boiling water-bath. Start timing. 14. Measure the time taken to the first appearance of a colour change in the test-tube. If there is no colour change after 120 seconds, stop timing and record as ‘more than 120’. 15. Record the result in (a)(ii). 16. Remove the test-tube from the water-bath and put it in the test-tube rack. 17. Repeat step 11 to step 16 with each of the other concentrations of sucrose solution. 18. Repeat step 11 to step 14 with the sample from U. 19. Record the result for U in (a)(iii). (ii) Record your results for the known concentrations of sucrose solution in an appropriate table.

(iii) State the time taken for the appearance of the first colour change for U. ........................................................ Complete Fig. 1.1 to show an estimate of the percentage concentration of sucrose solution in the sample U, using the letter U. [Fig. 1.1 with percentage scale] (iv) The concentration of sucrose in U can also be estimated from a graph of your results. Draw a graph using the results you recorded in (a)(ii) on the grid in Fig. 1.2. The axes have been labelled for you. Use a sharp pencil for drawing graphs. [Fig. 1.2 graph grid] (v) Use your graph and the time stated in (a)(iii) to estimate the percentage concentration of sucrose in U. Show on the graph how you determined your answer. percentage concentration of sucrose solution in U ........................................................ [1] (vi) Identify one significant source of error in this investigation. ........................................................ [1] (vii) A student carried out the same procedure to estimate the percentage concentration of sucrose solution in a different fruit extract. The estimate for the percentage concentration of sucrose solution was found to be below 2.0%. Apart from drawing a graph, suggest how the student could improve this procedure to obtain a more accurate estimate of the percentage concentration of sucrose solution in this fruit extract. ........................................................ [3] (b) Maturing fruits contain many types of sugar. The proportions of these different sugars vary according to the type of fruit. A scientist carried out some tests to determine the mass of each type of sugar found in one type of fruit. The total mass of the fruit was 55g. The results are shown in Table 1.3. [Table 1.3 with sugar types and masses] (i) Calculate the percentage of the fruit that is made up of sugars. Show all the steps in your working. percentage = ........................................................ [3] (ii) Draw a bar chart of the data shown in Table 1.3 on the grid in Fig. 1.3. Each bar should be separated for each type of sugar. Use a sharp pencil for drawing bar charts. [Fig. 1.3 bar chart grid] (iii) Name one source of the sucrose in the plant and the process used for loading the sucrose into the phloem tissue. source ........................................................ process ........................................................ [2]

K1 is a slide of a stained transverse section through a plant stem. You are not expected to be familiar with this specimen.
(a) Observe all the different tissues in the stem on K1 and select an area (sector) that shows the epidermis and vascular bundles.
Use a sharp pencil for drawings.
(i) Draw a large plan diagram of the sector you have selected on K1 to include:
• the epidermis
• one outer vascular bundle
• three inner vascular bundles (touching each other)
• any other observable tissues.
Use one ruled label line and label to identify the cortex.
You are expected to draw the correct shape and proportions of the different tissues. [5]
(ii) Observe the cells around the air spaces on K1. Select one group of four adjacent, touching cells along the side of an air space. Each cell must touch at least one of the other cells. Use the eyepiece graticule in the microscope to measure, as shown in Fig. 2.1:
• the total length of the four cells, L
• the depth of one of the cells, D.

L.............................. eyepiece graticule units
D.............................. eyepiece graticule units [1]
(iii) Use the measurements from (a)(ii) to help you make a large drawing of this group of four cells on K1.
Use one ruled label line and label to identify the cell wall of one cell. [4]
(iv) The tissues on K1 include air spaces. Suggest a habitat where K1 might grow.
.............................................................. [1]

(b) Fig. 2.2 is a photomicrograph of a stained transverse section through part of the stem of a different plant species.

A student calibrated the eyepiece graticule in a light microscope using a stage micrometer scale so that the actual width of the stem could be found.
The calibration was one eyepiece graticule division equal to 29.5μm.
Fig. 2.2 shows a photomicrograph taken using the same microscope with the same lenses as the student.
Use the calibration of the eyepiece graticule division and Fig. 2.2 to calculate the actual width of the stem, shown by line X–Y.
Show all the steps in your working and use appropriate units.
actual width of the stem = ............................................. [3]
Fig. 2.3 is the same photomicrograph without the eyepiece graticule scale and without the line X–Y.


(c) Annotate Fig. 2.3 to describe three observable differences between the stem sections in Fig. 2.3 and on K1 by:
• drawing label lines to three features in Fig. 2.3 that show these differences
• describing next to each line how each feature is different from the specimen on K1. [3]

K1 is a slide of a stained transverse section through a plant stem. You are not expected to be familiar with this specimen.
(a) Observe all the different tissues in the stem on K1 and select an area (sector) that shows the epidermis and vascular bundles.
Use a sharp pencil for drawings.
(i) Draw a large plan diagram of the sector you have selected on K1 to include:
• the epidermis
• one outer vascular bundle
• three inner vascular bundles (touching each other)
• any other observable tissues.
Use one ruled label line and label to identify the cortex.
You are expected to draw the correct shape and proportions of the different tissues. [5]
(ii) Observe the cells around the air spaces on K1. Select one group of four adjacent, touching cells along the side of an air space. Each cell must touch at least one of the other cells. Use the eyepiece graticule in the microscope to measure, as shown in Fig. 2.1:
• the total length of the four cells, L
• the depth of one of the cells, D.

L.............................. eyepiece graticule units
D.............................. eyepiece graticule units [1]
(iii) Use the measurements from (a)(ii) to help you make a large drawing of this group of four cells on K1.
Use one ruled label line and label to identify the cell wall of one cell. [4]
(iv) The tissues on K1 include air spaces. Suggest a habitat where K1 might grow.
.............................................................. [1]

(b) Fig. 2.2 is a photomicrograph of a stained transverse section through part of the stem of a different plant species.

A student calibrated the eyepiece graticule in a light microscope using a stage micrometer scale so that the actual width of the stem could be found.
The calibration was one eyepiece graticule division equal to 29.5μm.
Fig. 2.2 shows a photomicrograph taken using the same microscope with the same lenses as the student.
Use the calibration of the eyepiece graticule division and Fig. 2.2 to calculate the actual width of the stem, shown by line X–Y.
Show all the steps in your working and use appropriate units.
actual width of the stem = ............................................. [3]
Fig. 2.3 is the same photomicrograph without the eyepiece graticule scale and without the line X–Y.


(c) Annotate Fig. 2.3 to describe three observable differences between the stem sections in Fig. 2.3 and on K1 by:
• drawing label lines to three features in Fig. 2.3 that show these differences
• describing next to each line how each feature is different from the specimen on K1. [3]