Biology 0610/63 May/June 2019: question paper and mark scheme

Question

Fig. 1.1 shows a section through an unfertilised chicken’s egg. The egg is made up of the outer shell, inner yellow yolk and albumen (egg white). shell yolk albumen Fig. 1.1 The albumen and yolk are composed of different substances, including fats. (a) Describe how ethanol can be used to test a sample of food for the presence of fat. Include the result for a positive test. …… [3] (b) A student was given a sample of albumen. They tested the sample for reducing sugars by carrying out the steps shown: • a syringe was used to put 2 cm3 of albumen suspension into a test-tube • 2 cm3 of Benedict’s reagent was added • the solutions were mixed thoroughly by gently shaking the test-tube. (i) State the next step required to complete the test for reducing sugars. …… [1] (ii) Describe a positive result for the presence of reducing sugars. …… [1] (c) Proteins can be broken down by protease enzymes. Enzymes are also made of protein. A student investigated the effect of acid on the breakdown of albumen by a protease enzyme. Step 1 Three test-tubes P, Q and R were prepared. The volumes of the substances added to the test-tubes are shown in Table 1.1. Table 1.1 test-tube albumen distilled acid enzyme / cm3 water / cm3 / cm3 / cm3 P 2 2 0 0 Q 2 1 0 1 R 2 0 1 1 Step 2 The test-tubes were placed in a water-bath at 40 °C for 10 minutes. Step 3 After 10 minutes the test-tubes were removed from the water-bath and placed in a test-tube rack. 2 cm3 of biuret solution was added to each test-tube. Step 4 The appearance of the solution in each test-tube was observed. The student’s observations are shown in Fig. 1.2. P is a purple co lour Q is purple R is blue Fig. 1.2 (i) Prepare a table to record the observations shown in Fig. 1.2. [2] (ii) State a conclusion for these results. …… [1] (iii) Identify the variable that was changed (independent variable) in this investigation. …… [1] (iv) State the purpose of test-tube P in this investigation. …… [1] (v) Suggest why 1 cm3 of distilled water was added to test-tube Q. …… [1] (vi) The student used only one syringe to prepare the solutions in test-tubes P, Q and R in step 1. Explain why this is a potential source of error and how it could affect the results. error …… effect of the error …… [2] (vii) Identify one potential safety hazard in this investigation. …… [1] [Total: 14]

Question

(a) Fig. 2.1 is a photomicrograph showing a cross-section of an artery. Fig. 2.1 Make a large drawing of the artery in Fig. 2.1 to show the layers that make up the artery wall. Do not draw individual cells. [4] (b) Fig. 2.2 shows a photomicrograph of cross-sections of an artery and a vein. vein artery B A magnification ×13 Fig. 2.2 (i) The diameter of the artery is indicated by line AB. Measure the length of line AB, on Fig. 2.2. Include the unit. length of line AB …… Calculate the actual diameter of the artery using your measurement and the formula. length of line AB magnification = actual diameter of the artery Give your answer to two significant figures. Include the unit. Show your working. [3] (ii) Describe one similarity and one difference between the artery and the vein shown in Fig. 2.2. similarity …… difference …… [2] (c) A person investigated the change in their pulse rate before and after exercise. The person measured their pulse before exercise, during and after exercise. The results are shown in Table 2.1. Table 2.1 time pulse rate activity / minutes / beats per minute 2 78 before exercise 4 78 6 78 8 125 during exercise 10 148 12 160 14 154 after exercise 16 122 18 94 (i) Calculate the percentage increase in the pulse rate from minute 6 (before exercise) to minute 12 (during exercise). Give your answer to the nearest whole number. Show your working. …… % [2] (ii) Plot a line graph on the grid of time against pulse rate for the results shown in Table 2.1. [4] (iii) Use your graph to estimate the pulse rate of the person at 15 minutes. Show on your graph how you obtained your answer. …… bpm [2] (iv) Describe the results of the person’s investigation. …… [3] (d) Plan an investigation to find out how running at different speeds affects pulse rate. …… [6] [Total: 26]