Presentation of Data and Observations

As you carry out each test to identify the presence or absence of the biological molecule in S1, S2 and S3, complete the following:

Decide which biological molecule to identify in the first test.

First test: Test for ______

Describe how you used the reagents to carry out this test.

Carry out the first test and record your observations.

Use these observations to complete the sentence.

Solution(s) ______ contain(s) the biological molecule ______ .

Decide which biological molecule to identify in the second test.

Second test: Test for ______

Describe how you used the reagents to carry out this test.

Carry out the second test and record your observations.

Use these observations to complete the sentence.

Solution(s) ______ contain(s) the biological molecule ______ .

Decide which test you will use to check the identity of the third biological molecule.

Third test: Test for ______

Describe how you used the reagents to carry out this test.

Carry out the third test and record your observation.

Use this observation to complete one of the following sentences.

Solution(s) ______ contain(s) the biological molecule ______ .

OR

Solution ______ does not contain any of these biological molecules, glucose, starch or sucrose.

You are required to identify which of the other two biological molecules is hydrolysed by the enzyme, E using the procedure shown in Fig. 1.1 on each solution.

Set up two beakers as shown in Fig. 1.1.
Leave the mixtures for 5 minutes so that E can carry out the hydrolysis.
After 5 minutes, test the mixtures to find out whether E has hydrolysed the biological molecule to its products.

Prepare the space below to record:

• the biological molecule tested for
• the observations.

Calculate the curved surface area, to the nearest whole number, using $2 \times 3.14 \times r \times 20$.

curved surface area = ______

For the potato cylinders in P, use $\pi r^2$ to calculate the area of one circular end to the nearest whole number.
Use $\pi$ as 3.14 and use $r$ as recorded in (a)(i).

area of one circular end = ______

Complete Table 1.3 to calculate the total surface area when using different numbers of pieces to include:
• one whole cylinder
• one cylinder cut into two pieces
• two other cylinders cut into two different numbers of pieces.

Table 1.3

1. Cut each of the four cylinders into the number of pieces, as shown in Table 1.3.
2. Put the pieces into the shallow dish labelled C.
   Cover with a damp paper towel to prevent the pieces from drying out.

You will use the apparatus as shown in Fig. 1.4.

Fig. 1.4

1. Set up the test-tube with W and the delivery tube, as shown in Fig. 1.4 and described in (a)(v). Do not attach the tubing to the syringe. You may stand the test-tube in the test-tube rack provided.
2. Remove the plunger from the $10\ \text{cm}^3$ syringe.
3. Put potato tissue into the barrel of the syringe, for example the whole cylinder in one piece.
4. Replace the plunger and push it to the $4\ \text{cm}^3$ mark, as shown in Fig. 1.5.

Fig. 1.5

1. Put the nozzle of the syringe into the beaker containing H.
2. Pull the plunger out to the $10\ \text{cm}^3$ mark so that H enters the syringe, as shown in Fig. 1.6.

Fig. 1.6

1. Hold the syringe above the beaker containing H and push the plunger to adjust the level of H to the $5\ \text{cm}^3$ mark in the syringe, as shown in Fig. 1.7.

Fig. 1.7

1. Turn the syringe upside down so that the nozzle is up and there is air in the top of the syringe barrel. Carefully wipe the nozzle with a paper towel to remove excess H.
2. Tap the syringe barrel to make sure all the potato pieces are in H.
3. Attach the delivery tube to the nozzle to make an airtight fit.
4. Put the syringe into a beaker as shown in Fig. 1.4 (page 5).
5. Put the end of the delivery tube back into the test-tube as described in (a)(v).
6. Start timing when the first bubble is observed in the water in the test-tube.
7. Count the bubbles at intervals of 30 seconds up to 120 seconds. Record the results in (a)(vi).
8. Using a paper towel to avoid H coming into contact with your skin, remove the delivery tube from the syringe, keeping the syringe nozzle up.
9. Then push the plunger to empty as much as possible of H into the container labelled 'For waste'.
10. Slowly pull out the plunger and put the potato tissue and remaining H into the container labelled 'For waste'.
11. Repeat step 6 to step 20 with both of the pieces from the cylinder cut into two pieces.
12. Repeat step 6 to step 20 with each of the other two cylinders which have been cut into different numbers of pieces.

Record your results for the total surface area as shown in Table 1.3 and the number of bubbles at each 30 seconds in an appropriate table.

Using the results in (a)(vi), calculate for the largest surface area:
• the mean number of bubbles in 30 seconds
• the rate of activity, $\text{number min}^{-1}$.

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

mean number of bubbles = ______

rate of activity = ______

Complete Fig. 1.1 to show how you will prepare your serial dilution.

Each beaker should have:

• a labelled arrow to show the volume of hydrochloric acid transferred
• a labelled arrow to show the volume of distilled water, W, added
• a label under each beaker to show the concentration of the hydrochloric acid.

Carry out step 1 to step 10.

step 1 Prepare the concentrations of hydrochloric acid as shown in Fig. 1.1.

step 2 Label one test-tube containing blue agar with the label U.

step 3 Label the other test-tubes containing blue agar with the concentrations of hydrochloric acid prepared in step 1.

step 4 Put $1\ \text{cm}^3$ of $2.0\ \text{mol dm}^{-3}$ hydrochloric acid, H, into the appropriately labelled test-tube.

step 5 Put $1\ \text{cm}^3$ of each of the other concentrations of hydrochloric acid, as prepared in step 1, into the appropriately labelled test-tube.

step 6 Put $1\ \text{cm}^3$ of the unknown concentration of hydrochloric acid, U, into the test-tube labelled U.

In step 7 and step 9 you will need to wait for 10 minutes. While you are waiting, use your time to continue with other parts of Question 1.

step 7 Start timing and wait for 10 minutes.

step 8 After the 10 minutes, measure the depth of yellow agar (diffusion distance), shown in Fig. 1.2, for each concentration of hydrochloric acid and for U. Record your results in (a)(ii).

step 9 Continue timing and wait for a further 10 minutes (20 minutes in total).

step 10 After the 10 minutes, measure the depth of yellow agar (diffusion distance) for each concentration of hydrochloric acid and U. Record your results in (a)(ii).

Record your results in an appropriate table.

For the $2.0\ \text{mol dm}^{-3}$ hydrochloric acid, calculate the rate of diffusion over 20 minutes.

Show your working and use appropriate units.

rate of diffusion = ______

Plot a graph of the data shown in Table 1.2 on the grid in Fig. 1.3.

Use a sharp pencil.

Prepare the space below to show your measurements and calculations.

Show all the steps in your calculation of the mean.

mean surface area of the beads = ______ $\text{mm}^2$

A student suggested that it was possible to investigate the independent variable, surface area, by changing the number of beads. The maximum number of beads used was 20. Decide the other numbers of beads to use and state the different number of beads you will use.

Carry out the student’s procedure.

1. Label as many small test-tubes as you will need with the number of beads for each test-tube.
2. Put $10\ \text{cm}^3$ of solution G into each test-tube.
3. Put $1\ \text{cm}^3$ of B into each test-tube. Put the bung in each test-tube in turn and mix.
4. If the contents of the test-tube are not blue, add one drop at a time of A to the contents of each test-tube to turn them all the same blue colour.
5. Put the required number of beads into each test-tube.
6. Put the bung in each test-tube in turn and mix contents. Mix every 2 minutes for 6 minutes.
7. Record your observations after each 2 minutes, up to 6 minutes.

Prepare the space below to record your observations.

1. Using the information in step 5 and (b)(i), find the colour of the pH indicator solution with pH 3, pH 4, W, S1 and S2. Record all your observations in (b)(ii).

Prepare the space below and record all your observations.

Fig. 1.1 shows the position of pH 7 on a scale.
Using your results in (b)(ii) complete Fig. 1.1 to show:

• the positions of pH 3, pH 4 and pH 6 on the scale
• the positions of W, S1 and S2 on the scale.

Plot a graph of the data shown in Table 1.2.

Use your graph to estimate the absorbance of light at $40^{\circ}\text{C}$.
Show on your graph how you estimated the absorbance of light.

absorbance = ______

Prepare the space below to record

• the time you remove each sample and
• the time at which the end-point is reached and
• the time taken to reach the end-point.

Plot a graph of the data shown in Table 1.1.

Use your graph to find the rate of hydrolysis of the sucrose by finding the gradient of the line.

Show on your graph where you took the readings to calculate the gradient.

Show all the steps in your calculation.

rate of enzyme activity = ______ $\text{mg s}^{-1}$

Calculate the ratio of the mean of the total width of the section to the mean width of the outer skin.

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

Table 2.1 shows some of the components in $100\ \text{g}$ of plantain and sweet banana.

Table 2.1

Plot a chart of the data in Table 2.1.

The components in Table 2.1 make up a certain percentage of the total mass of the plantain and sweet banana. Water makes up the balance of the total mass.

Calculate the difference in percentage water content between plantain and sweet banana.

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

______ %

Complete Table 1.1.

Table 1.1

Prepare the space below and record your results.

Table 1.2 shows the results of this investigation.

Table 1.2

Plot a graph of the data shown in Table 1.2.

Carry out step 1 to step 9.

step 1 Set up a water-bath using the beaker of water labelled water-bath and heat it to boiling, ready for step 6.

step 2 In the beakers provided, prepare the concentrations of reducing sugar solution as shown in Fig. 1.3.

step 3 Label five test-tubes with the concentrations you prepared in step 2.

step 4 Put $2\,\text{cm}^3$ of each reducing sugar concentration into the appropriately labelled test-tube.

step 5 Put $2\,\text{cm}^3$ of Benedict's solution into each of the test-tubes. Shake gently to mix.

step 6 Put the test-tube containing $1.00\%$ reducing sugar solution into the boiling water-bath. Start timing.

step 7 Record, in (a)(ii), the time taken to the first appearance of a colour change.

If there is no colour change after 120 seconds, stop timing and record the result as 'more than 120'.

step 8 Remove the test-tube from the boiling water-bath.

step 9 Repeat step 6 to step 8 with the remaining concentrations of reducing sugar.

You will need the boiling water-bath again in step 13.

Record your results in an appropriate table.

You will now collect results to estimate the concentration of reducing sugars in samples G1 and H1.

Carry out step 10 to step 16.

step 10 Label two test-tubes G1 and H1.

step 11 Put $2\,\text{cm}^3$ of G1 into the appropriately labelled test-tube.

step 12 Put $2\,\text{cm}^3$ of Benedict's solution into the test-tube. Shake gently to mix.

step 13 Put the test-tube into the boiling water-bath. Start timing.

step 14 Record, in (a)(iv), the time taken to the first appearance of a colour change.

If there is no colour change after 120 seconds, stop timing and record the result as 'more than 120'.

step 15 Remove the test-tube from the boiling water-bath.

step 16 Repeat step 11 to step 15 with H1.

Record your results for G1 and H1.

result for G1 = ______ $\text{s}$

result for H1 = ______ $\text{s}$

Fig. 1.4 shows a scale of reducing sugar concentrations from $1.00\%$ to $0.00\%$.

Complete the scale in Fig. 1.4 so that it shows, in the correct positions, all the reducing sugar concentrations you prepared in step 2.

Use your results in (a)(ii) and (a)(iv) to estimate the concentrations of reducing sugars in G1 and H1.

Show your estimates for G1 and H1 on Fig. 1.4 by drawing arrows ($\downarrow$) at the correct positions on the scale. Label one arrow G1 and the other arrow H1.

Plot a graph of the data in Table 1.2 on the grid in Fig. 1.5.

Use a sharp pencil.

Fig. 1.5

Use your graph to estimate the activity of amylase at 60 hours after germination.

activity of amylase = ______ $\text{au}$

Carry out step 11 to step 19.

step 11 Set up a boiling water-bath ready for step 16.

step 12 Prepare the concentrations of glucose solutions as shown in Fig. 1.3.

step 13 Label 5 test-tubes with the concentrations prepared in step 12.

step 14 Put $1\ \text{cm}^3$ of each glucose concentration into the appropriately labelled test-tube.

step 15 Put $1\ \text{cm}^3$ of Benedict's into each of the test-tubes. Shake gently to mix.

step 16 Put the test-tube containing 1.0% glucose solution into the boiling water-bath. Start timing.

step 17 Record in (a)(ii) the time to the first colour change.

If there is no colour change after 120 seconds, stop timing and record the time as 'more than 120'.

step 18 Remove the test-tube from the boiling water-bath.

step 19 Repeat step 16 to step 18 with the other glucose concentrations.

You will need the boiling water-bath again in step 25.

Record your results in an appropriate table.

Carry out step 20 to step 23.

step 20 Label a small test-tube R1.

step 21 After 15 minutes (step 8), put a $1\ \text{cm}^3$ syringe into the water surrounding the dialysis tubing containing R, so that the end of the syringe is level with the mark on the test-tube. Remove $1\ \text{cm}^3$ from the water surrounding the dialysis tubing and put this into the test-tube labelled R1.

step 22 Label a small test-tube S1.

step 23 After 15 minutes (step 10), put a $1\ \text{cm}^3$ syringe into the water surrounding the dialysis tubing containing S, so that the end of the syringe is level with the mark on the test-tube. Remove $1\ \text{cm}^3$ from the water surrounding the dialysis tubing and put this into the test-tube labelled S1.

You will determine the concentrations of glucose in R1 and S1 by:

• carrying out the Benedict's test on R1 and S1
• using your results to estimate the concentration of glucose in R1 and S1.

Estimating the concentration of glucose in samples R1 and S1

Carry out step 24 to step 28.

step 24 Put $1\ \text{cm}^3$ of Benedict's into the test-tube labelled R1. Shake gently to mix.

step 25 Put the test-tube into the boiling water-bath. Start timing.

step 26 Record in (a)(iii) the time to the first colour change.

If there is no colour change after 120 seconds, stop timing and record the time as 'more than 120'.

step 27 Remove the test-tube from the boiling water-bath.

step 28 Repeat step 24 to step 27 with the test-tube labelled S1.

Record your results for R1 and S1.

result for R1 = ______ $\text{s}$
result for S1 = ______ $\text{s}$

Calculate the average rate at which the percentage concentration of glucose is increasing in the water surrounding the dialysis tubing containing R.

Show your working and give your answer to two significant figures.

average rate of increase of percentage concentration of glucose = ______ per minute

Draw a bar chart of the data in Table 1.3 on the grid in Fig. 1.4.

Use a sharp pencil.

Calculate the percentage difference in the mass of sucrose per $100\ \text{g}$ of pineapple compared to the mass of sucrose per $100\ \text{g}$ of apple.

Show your working.

percentage difference in the mass of sucrose = ______