Biology 0610/62 October/November 2019: question paper and mark scheme

Question

A student investigated the effect of the enzyme amylase on the breakdown of a starch suspension. The starch suspension was placed inside a bag made from dialysis tubing. amylase starch reducing sugars Dialysis tubing is made from a type of membrane that is partially permeable. Only small molecules can pass through this membrane. Step 1 Two large test-tubes were put into a water-bath. Each large test-tube contained 20 cm3 of distilled water. The temperature of the water-bath was 40 °C. Step 2 A knot was tied at the end of one piece of dialysis tubing, to form a bag. Step 3 5 cm3 of the starch suspension was put into the dialysis tubing bag. Step 4 A clean syringe was used to put 5 cm3 of amylase solution into the dialysis tubing bag. Step 5 The contents of the dialysis tubing bag were mixed well and the outside of the bag was rinsed with distilled water. Step 6 The student repeated steps 2 to 5 using 5 cm3 of distilled water in step 4 instead of the amylase solution. Step 7 The dialysis tubing bags were placed into the large test-tubes as shown in Fig. 1.1. large test-tube 20 cm3 distilled water dialysis tubing bag knotted end dialysis tubing bag 1 containing dialysis tubing bag 2 containing amylase and starch suspension water and starch suspension Fig. 1.1 Step 8 Both large test-tubes were placed back into the water-bath and left for 10 minutes. Step 9 After 10 minutes the dialysis tubing bags were removed from the two large test-tubes. Step 10 The contents of the two large test-tubes and the two dialysis tubing bags were tested for reducing sugars and starch. (a) State the name of the solution that the student would use to test substances for starch. …… [1] (b) Describe how the student would test substances for reducing sugars. …… [2] (c) Suggest why the outside of the dialysis tubing bag was rinsed in Step 5. …… [1] The student’s observations for the starch and reducing sugar tests in step 10 are shown in Fig. 1.2. dialysis tubing bag 1 contents: test-tube 1 dialysis tubing contents starch test colour was brown bag 1 contents reducing sugar test colour was brick-red test-tube 1 contents: starch test colour was brown reducing sugar test colour was orange dialysis tubing bag 1 containing amylase and starch suspension at the start of the investigation dialysis tubing bag 2 contents: test-tube 2 dialysis tubing contents starch test colour was blue-black bag 2 contents reducing sugar test colour was blue test-tube 2 contents: starch test colour was brown reducing sugar test colour was blue dialysis tubing bag 2 containing water and starch suspension at the start of the investigation Fig. 1.2 (d) (i) Prepare a table and record the results of the starch and reducing sugar tests from Fig. 1.2 in the space provided. [3] (ii) State three conclusions for the results shown in Fig. 1.2. …… [3] (e) State two variables that were kept constant during this investigation. 1 …… 2 …… [2] (f) Plan an investigation using dialysis tubing to determine the effect of temperature on the activity of the enzyme amylase. …… [6] (g) The student wanted to find out if the amylase enzyme passed through the dialysis tubing into the large test-tube. Amylase is made of protein. Describe how the student could find out if the solution in the large test-tube contained protein. …… [2] [Total: 20]

Question

An investigation was performed to determine the effect of light intensity on leaf size in one species of plant. Plants were grown in three different light intensities. The maximum width of each leaf was recorded. The results were recorded in Table 2.1 and an average value was calculated. The results for three leaves grown in high light intensity are shown in Fig. 2.1. The horizontal line on each leaf indicates its maximum width. 6 7 8 Fig. 2.1 (a) (i) Measure the widths of leaves 6, 7 and 8 in Fig. 2.1 and record these values in Table 2.1. [1] Table 2.1 maximum width of leaves / mm leaf low light intensity medium light intensity high light intensity 1 15 43 27 2 12 45 32 3 13 48 26 4 13 44 28 5 15 47 27 6 14 43 7 12 12 8 15 46 average 14 41 (ii) Calculate the average width of the leaves grown in a high light intensity in Table 2.1. Record this value in Table 2.1. [1] (iii) Plot a bar chart on the grid of the average leaf width for leaves grown in low, medium and high light intensity using the data in Table 2.1. [3] (iv) Circle one measurement in Table 2.1 that could be considered to be anomalous. Give a reason for your choice. reason …… …… [2] (b) (i) State the variable that was changed in this investigation (the independent variable). …… [1] (ii) State the variable that was measured in this investigation (the dependent variable). …… [1] (c) Fig. 2.2 is a photomicrograph of a cross-section of a root. xylem A B Fig. 2.2 (i) Make a large drawing of the cross-section of the root in Fig. 2.2 to show the different areas of the root. Do not draw individual cells. [4] (ii) Measure line AB on Fig. 2.2 in millimetres. length of line AB …… mm The actual diameter of the root shown in Fig. 2.2 is 2 mm. Calculate the magnification of Fig. 2.2 using the equation. magnification = length of line AB on Fig. 2.2 actual diameter of the root [2] (iii) Fig. 2.3 is a photomicrograph of a cross-section of a stem. xylem magnification ×20 Fig. 2.3 State two differences between the root in Fig. 2.2 and the stem in Fig. 2.3. 1 …… 2 …… [2] (d) A student suggested that measuring leaf area is better than measuring leaf width. (i) Describe how the area of a leaf could be measured. …… [2] (ii) Suggest why measuring leaf area is better than measuring leaf width. …… [1] [Total: 20]