AS & A Level Biology - 9700 Paper 3 2018 Summer Zone 4

(a) You will need to make a serial dilution of 15% ethanol, E, which reduces the concentration by half between each successive dilution. You will need to prepare 20 cm$^3$ of each concentration of ethanol.
Fig. 1.1 shows the first two beakers you will use to make your serial dilution.
(i) Complete Fig. 1.1 by drawing as many extra beakers as you need for your serial dilution.
For each beaker:
• state, under the beaker, the volume and concentration of ethanol available for use in the investigation
• use one arrow, with a label above the beaker, to show the volume and concentration of ethanol added to prepare the concentration of ethanol in the beaker
• use another arrow, with a label above the beaker, to show the volume of W added to prepare the concentration of ethanol in the beaker.
The first beaker in Fig. 1.1 has been labelled for you.


(ii) Record your results in an appropriate table, including:
• colour
• pH.
(iii) State the colour and pH for U at 9 minutes.
colour ........................................................
pH ...............................................................
Complete Fig. 1.2 to show:
• the percentage concentrations of ethanol prepared in step 1
• the estimated percentage concentration of ethanol in U, using the letter U.


(iv) The student's hypothesis stated that:
Concentrations of ethanol below 15% will continue to cause the death of yeast cells.
State whether you support or you reject this hypothesis.
Explain how your results provide evidence for this decision.
support or reject ..................................
explanation ..................................................................................................
.................................................................[2]

(v) Identify one significant source of error in this investigation.
.................................................................................................................................[1]

(b) A student investigated the activity of a yeast cell suspension and glucose by measuring the release of carbon dioxide given off over a period of 11 minutes.
The carbon dioxide was measured by recording the volume of gas collected in a graduated test-tube.
The temperature was kept constant at 25°C. All other variables were standardised.
The results are shown in Table 1.2.
[Table_1]
(i) Plot a graph of the data in Table 1.2 on the grid in Fig. 1.3.
Use a sharp pencil for drawing graphs.


(ii) Use your graph to calculate the rate of carbon dioxide given off between 7 minutes and 10 minutes.
Show all the steps in your working and use appropriate units.
rate = ....................................... au min$^{-1}$ [2]

(iii) The student investigated the release of carbon dioxide from a yeast cell suspension using the apparatus shown in Fig. 1.4.

Describe how you would modify this investigation to determine the effect of temperature on the release of carbon dioxide from a yeast cell suspension.
.............................................................................................................................................[3]

(a) You will need to make a serial dilution of 15% ethanol, E, which reduces the concentration by half between each successive dilution. You will need to prepare 20 cm$^3$ of each concentration of ethanol.
Fig. 1.1 shows the first two beakers you will use to make your serial dilution.
(i) Complete Fig. 1.1 by drawing as many extra beakers as you need for your serial dilution.
For each beaker:
• state, under the beaker, the volume and concentration of ethanol available for use in the investigation
• use one arrow, with a label above the beaker, to show the volume and concentration of ethanol added to prepare the concentration of ethanol in the beaker
• use another arrow, with a label above the beaker, to show the volume of W added to prepare the concentration of ethanol in the beaker.
The first beaker in Fig. 1.1 has been labelled for you.


(ii) Record your results in an appropriate table, including:
• colour
• pH.
(iii) State the colour and pH for U at 9 minutes.
colour ........................................................
pH ...............................................................
Complete Fig. 1.2 to show:
• the percentage concentrations of ethanol prepared in step 1
• the estimated percentage concentration of ethanol in U, using the letter U.


(iv) The student's hypothesis stated that:
Concentrations of ethanol below 15% will continue to cause the death of yeast cells.
State whether you support or you reject this hypothesis.
Explain how your results provide evidence for this decision.
support or reject ..................................
explanation ..................................................................................................
.................................................................[2]

(v) Identify one significant source of error in this investigation.
.................................................................................................................................[1]

(b) A student investigated the activity of a yeast cell suspension and glucose by measuring the release of carbon dioxide given off over a period of 11 minutes.
The carbon dioxide was measured by recording the volume of gas collected in a graduated test-tube.
The temperature was kept constant at 25°C. All other variables were standardised.
The results are shown in Table 1.2.
[Table_1]
(i) Plot a graph of the data in Table 1.2 on the grid in Fig. 1.3.
Use a sharp pencil for drawing graphs.


(ii) Use your graph to calculate the rate of carbon dioxide given off between 7 minutes and 10 minutes.
Show all the steps in your working and use appropriate units.
rate = ....................................... au min$^{-1}$ [2]

(iii) The student investigated the release of carbon dioxide from a yeast cell suspension using the apparatus shown in Fig. 1.4.

Describe how you would modify this investigation to determine the effect of temperature on the release of carbon dioxide from a yeast cell suspension.
.............................................................................................................................................[3]

In order to observe yeast cells using a light microscope, they are often stained. You will need to observe the effects of two stains, methylene blue solution and iodine solution.

You are provided with the material shown in Table 2.1.

[Table_1]

It is recommended that you wear suitable eye protection.
If M or I come into contact with your skin, wash off immediately under cold water.

You will need to use the microscope to observe the colour of the yeast cells both before and after adding the stains, M and I. You will record your observations using annotated drawings.

Read step 1 to step 12 before proceeding.

1. Label 3 clean, dry microscope slides with the letters Y, M and I.
2. Put the slide labelled Y on a paper towel.
3. Put a few drops of yeast cell suspension Y onto the slide.
4. Cover the yeast cells with a coverslip and use a paper towel to remove any excess liquid that is outside the coverslip.
5. Use the microscope to view the yeast cells on the slide.

You may need to reduce the amount of light entering the microscope to observe the cells clearly.

(a) (i) Select 3 whole yeast cells from slide Y. Make a large drawing of these yeast cells in box Y in Fig. 2.1.

Use a sharp pencil for drawings.

6. Remove the slide from the microscope and place on a paper towel.
7. Put the slide labelled M on a paper towel.
8. Put a few drops of yeast cell suspension Y onto the slide.
9. Put a drop of M onto the slide in order to stain the yeast cells.
10. Cover the yeast cells with a coverslip and use a paper towel to remove any excess liquid that is outside the coverslip.
11. Use the microscope to view the yeast cells on the slide.

12. Repeat step 6 to step 11 using I instead of M.

(ii) Select 3 whole yeast cells from slide M. Make a large drawing of these yeast cells in box M in Fig. 2.1.
(iii) Select 3 whole yeast cells from slide I. Make a large drawing of these yeast cells in box I in Fig. 2.1.



(iv) Annotate your drawings in Fig. 2.1 to describe:

• one observable difference between the yeast cells on slide Y compared to yeast cells stained with M
and
• one observable difference between the yeast cells on slide Y compared to yeast cells stained with I.

[3]+[2]

(b) Fig. 2.2 is a photomicrograph of yeast cells.



Make a large drawing of the 5 whole cells shown in the area on Fig. 2.2.

[4]

(c) Fig. 2.3 is a photomicrograph of a stained transverse section through two blood vessels, B1 and B2.



(i) Draw large plan diagrams of the two blood vessels, B1 and B2, shown in Fig. 2.3.

You are expected to draw the correct shape and proportions of the different tissues.

[4]

(ii) Annotate your drawings in (c)(i) to describe three observable differences between B1 and B2 by:
• drawing label lines to B1 and to B2 that show these differences
• describing next to each line how each feature is different.

[3]

(iii) State which blood vessel, B1 or B2, carries blood under high pressure. Give one reason for your choice.

blood vessel ..........................................................
reason ...............................................................

[1]

(iv) Use the scale bar in Fig. 2.3 to calculate the magnification of Fig. 2.3.

Show all the steps in your working and use appropriate units.

magnification \times .................................................

[2]

In order to observe yeast cells using a light microscope, they are often stained. You will need to observe the effects of two stains, methylene blue solution and iodine solution.

You are provided with the material shown in Table 2.1.

[Table_1]

It is recommended that you wear suitable eye protection.
If M or I come into contact with your skin, wash off immediately under cold water.

You will need to use the microscope to observe the colour of the yeast cells both before and after adding the stains, M and I. You will record your observations using annotated drawings.

Read step 1 to step 12 before proceeding.

1. Label 3 clean, dry microscope slides with the letters Y, M and I.
2. Put the slide labelled Y on a paper towel.
3. Put a few drops of yeast cell suspension Y onto the slide.
4. Cover the yeast cells with a coverslip and use a paper towel to remove any excess liquid that is outside the coverslip.
5. Use the microscope to view the yeast cells on the slide.

You may need to reduce the amount of light entering the microscope to observe the cells clearly.

(a) (i) Select 3 whole yeast cells from slide Y. Make a large drawing of these yeast cells in box Y in Fig. 2.1.

Use a sharp pencil for drawings.

6. Remove the slide from the microscope and place on a paper towel.
7. Put the slide labelled M on a paper towel.
8. Put a few drops of yeast cell suspension Y onto the slide.
9. Put a drop of M onto the slide in order to stain the yeast cells.
10. Cover the yeast cells with a coverslip and use a paper towel to remove any excess liquid that is outside the coverslip.
11. Use the microscope to view the yeast cells on the slide.

12. Repeat step 6 to step 11 using I instead of M.

(ii) Select 3 whole yeast cells from slide M. Make a large drawing of these yeast cells in box M in Fig. 2.1.
(iii) Select 3 whole yeast cells from slide I. Make a large drawing of these yeast cells in box I in Fig. 2.1.



(iv) Annotate your drawings in Fig. 2.1 to describe:

• one observable difference between the yeast cells on slide Y compared to yeast cells stained with M
and
• one observable difference between the yeast cells on slide Y compared to yeast cells stained with I.

[3]+[2]

(b) Fig. 2.2 is a photomicrograph of yeast cells.



Make a large drawing of the 5 whole cells shown in the area on Fig. 2.2.

[4]

(c) Fig. 2.3 is a photomicrograph of a stained transverse section through two blood vessels, B1 and B2.



(i) Draw large plan diagrams of the two blood vessels, B1 and B2, shown in Fig. 2.3.

You are expected to draw the correct shape and proportions of the different tissues.

[4]

(ii) Annotate your drawings in (c)(i) to describe three observable differences between B1 and B2 by:
• drawing label lines to B1 and to B2 that show these differences
• describing next to each line how each feature is different.

[3]

(iii) State which blood vessel, B1 or B2, carries blood under high pressure. Give one reason for your choice.

blood vessel ..........................................................
reason ...............................................................

[1]

(iv) Use the scale bar in Fig. 2.3 to calculate the magnification of Fig. 2.3.

Show all the steps in your working and use appropriate units.

magnification \times .................................................

[2]