AS & A Level Biology - 9700 Paper 3 2015 Summer Zone 4

(a) State the hazard with the greatest level of risk when using the apparatus and reagents in step 1 on page 4. State the level of risk of the procedure: low or medium or high.
hazard .................................................................................................................................
level of risk ..........................................................

(b) (i) You are required to make a serial dilution of the 0.3% solution of X which reduces the concentration of X by a factor of 10 between each successive dilution. You will need to prepare 10 cm³ of each concentration of solution X. You should use the beakers shown in Fig. 1.1 to show how you will prepare the serial dilutions. You will need to use 9 cm³ of each different concentration of X in the investigation.
For each beaker, complete Fig. 1.1 to show how you will dilute the solution by:
• stating, under the beaker, the concentration and volume of the solution available for use in the investigation
• using one arrow, with a label above the beaker, to show the concentration and volume of the solution X added to prepare the concentration
• using another arrow, with a label above the beaker, to show the volume of W added to prepare the concentration.

(ii) Prepare the space below and record your results.

You are required to find the rate of activity of the catalase by measuring the time taken to collect 2 cm³ of oxygen produced by the hydrolysis of H. You are going to collect the oxygen released by displacement of water as shown in Fig. 1.2. The sealed syringe is full of water and is upside down over the end of the delivery tube. You need to time how long it takes for the bubbles of oxygen to push (displace) 2 cm³ of the water out of the syringe.
14. Put 5 cm³ of H into a clean test-tube.
15. Put 10 cm³ of the mixture of P and W into this test-tube.
16. Put the bung (with the delivery tube attached) into this test-tube.
17. Fill the sealed syringe with water from the beaker and turn it upside down keeping the open end of the syringe under the water as shown in Fig. 1.2.
18. Immediately put the end of the delivery tube into the beaker of water so that the bubbles of oxygen pass into the syringe.
19. Start timing.
(iii) Record the time for 2 cm³ of oxygen to be collected.
time ...............................................................
Using your recorded time, calculate the rate of activity of the catalase in cm³ s⁻¹. You may lose marks if you do not show your working and do not use the appropriate units.
rate of activity ............................................................... cm³ s⁻¹

(iv) Using your knowledge of enzymes, suggest how solution X may be changing the activity of the catalase.
.......................................................................................................................................
.......................................................................................................................................
.......................................................................................................................................
.......................................................................................................................................

(v) Identify one significant source of error when using each of the two methods to measure the dependent variable.
one significant error in counting the number of bubbles
.......................................................................................................................................
.......................................................................................................................................
one significant error in measuring the displacement of water
.......................................................................................................................................
.......................................................................................................................................

(vi) This first procedure investigated the effect of the concentration of X on the activity of catalase in the plant extract. To modify this procedure for investigating another variable, the independent variable (concentration of X) would need to be standardised. Describe how the independent variable (concentration of X) will be standardised.
.......................................................................................................................................
.......................................................................................................................................
Consider how you would modify this procedure to investigate the effect of temperature on the activity of the catalase in the plant extract.
Describe how the independent variable, temperature, will be investigated.
.......................................................................................................................................
.......................................................................................................................................

In an investigation into the circulation of blood in giraffes, it has been found that as the length of the neck increases the thickness of the muscle wall of the left ventricle increases. The results for five giraffes are shown in Table 2.1.

[Table_1]

You are required to use a sharp pencil for graphs.
(a) (i) Plot a graph of the data in Table 2.1.


(ii) A giraffe was found to have a neck length of 95.0 cm. Using the graph, estimate the thickness of the muscle wall in the left ventricle.............................. mm [1]

(iii) Suggest one reason for the relationship shown in the graph......................................................[1]

(b) Fig. 2.1 shows four photomicrographs of stained transverse sections through blood vessels, Q, R, S and T.

Fig. 2.1
(i) Choose one of the blood vessels shown in Fig. 2.1 which carries blood away from the heart. State the blood vessel, Q, R, S or T, which you have chosen .................... Draw a large plan diagram of this blood vessel.

A student observed a blood vessel from a different specimen. The student determined the ratio of the widest diameter of the blood vessel to the thickness of the blood vessel wall, using the actual measurements shown below.

[Table_2]

However, a ratio may be simplified by dividing each side by the same number to give the smallest possible whole number on each side. In this example, both sides of the ratio 1460:75 are divisible by 5, so the simplest ratio is 292:15.
(ii) Determine the simplest ratio of the mean diameter of the blood vessel S to the mean thickness of the wall of the blood vessel in Fig. 2.1.

On Fig. 2.1 show where you take your measurements.
You may lose marks if you do not show all the steps in your working.
ratio ............................................[4]

(c) M1 is a slide of a stained transverse section through a plant stem. This plant species grows throughout the world.
You are not expected to be familiar with this specimen.

(i) Observe one large vascular bundle. Select one group of four adjacent xylem vessel elements with at least two of the vessel elements touching. Make a large drawing of this group of four xylem vessel elements. Use one ruled label line and label to identify one lumen. [5]

(ii) Describe one observable difference between the structure of the xylem vessel elements drawn in (c)(i) and the structure of the blood vessels in Fig. 2.1.............................................................[1]

(iii) Suggest one observable feature, shown by both the specimen on M1 and Fig. 2.1, which supports the conclusion that these structures transport materials. Explain how this feature may help the transport of materials in the vessel elements in M1.

feature ..........................................................................................................
explanation ..........................................................................................[1]