Biology 0610/51 October/November 2021: question paper and mark scheme

Question

(a) Dialysis tubing can act as a partially permeable membrane because it has microscopic holes that allow small soluble molecules to pass through by diffusion. You are going to investigate the molecules that can diffuse through dialysis tubing. Read all the instructions but DO NOT CARRY THEM OUT until you have drawn a table for your results in the space provided in 1(a)(i). You should use the safety equipment provided while you are carrying out the practical work. Step 1 Remove the piece of dialysis tubing from the beaker of water labelled W. It has been knotted at one end to form a bag. Gently rub the unknotted end of the dialysis tubing until it is open. Step 2 Use a syringe to put 10 cm3 of solution M into the open end of the dialysis tubing bag. Step 3 Hold the open end of the bag and rinse the outside of the dialysis tubing by dipping it into the water in beaker W. Step 4 Place the dialysis tubing bag inside the large test-tube labelled T so that approximately 2 cm of the dialysis tubing folds over the top of the test-tube. Secure it with an elastic band, as shown in Fig. 1.1. Step 5 Use a measuring cylinder to pour warm distilled water into large test-tube T so that it covers the dialysis tubing bag, as shown in Fig. 1.1. open end of the dialysis tubing folded over the top of large elastic band test-tube T solution M inside the dialysis tubing bag warm distilled water knotted end of the dialysis tubing bag Fig. 1.1 Step 6 Leave large test-tube T in the test-tube rack for 15 minutes. Continue with the other questions while you are waiting. Step 7 Label a small beaker T. After 15 minutes remove the dialysis tubing bag from large test-tube T and put it in the waste container. Pour the liquid from large test-tube T into beaker T. Step 8 Label six clean test-tubes A, B, C, D, E and F. Step 9 Use a syringe to put 2 cm3 samples of solution M into test-tubes A, B and C. Step 10 Use a clean syringe to put 2 cm3 samples of liquid T into test-tubes D, E and F. Step 11 Test the contents of test-tubes A and D for reducing sugars using the correct food-testing reagent. Raise your hand when you are ready for hot water to be added to the beaker labelled water‑bath. Step 12 Test the contents of test-tubes B and E for protein using the correct food-testing reagent. Step 13 Test the contents of test-tubes C and F for starch using the correct food-testing reagent. Record your results from steps 11, 12 and 13 in your table in 1(a)(i). (i) Prepare a table to record your results from steps 11 to 13 in the space provided. Include the final colours of the food tests for each test-tube. [4] (ii) State the names of the food-testing reagents that you used to test for the presence of each substance. reducing sugars …… protein …… starch …… [2] (iii) State which substances are present in solution M. …… [1] (iv) Conclude, based on your results, if any of the substances in solution M diffused through the dialysis tubing membrane. State the evidence from your results for this conclusion. substance(s) …… evidence …… [1] (b) Explain why it was important to rinse the outside of the dialysis tubing bag in step 3. …… [1] (c) Identify one hazard in the investigation described in 1(a) and state one precaution taken to reduce the risk of this hazard. hazard …… precaution …… [2] (d) Starch can be broken down into reducing sugars. The enzyme amylase catalyses this reaction. Plan an investigation to find out the effect of pH on the activity of the enzyme amylase. …… [6] [Total: 17]

Question

(a) A student used an aquatic plant to investigate the effect of temperature on the rate of photosynthesis. Fig. 2.1 shows the apparatus used by the student. gas collecting in the measuring cylinder measuring cylinder containing water funnel lamp beaker containing water 10 cm aquatic plant producing gas Fig. 2.1 A lamp was placed at a distance of 10 cm from the apparatus. Sodium hydrogencarbonate was added to the water to provide a source of carbon dioxide. The student measured the volume of gas produced in 20 minutes at six different temperatures. (i) State the variable that was changed (independent variable) in this investigation. …… [1] (ii) State two variables that should be kept constant in this investigation. 1 …… 2 …… [2] (iii) Only one set of results was collected in the investigation described in 2(a). Explain why repeating the investigation two more times would be an improvement to the method. …… [1] (b) The results of the investigation are shown in Table 2.1. Table 2.1 volume of gas collected in temperature rate of photosynthesis 20 minutes / °C / cm3 per minute / cm3 5 5.0 0.25 10 7.8 0.39 15 12.0 0.60 20 22.8 1.14 25 21.0 1.05 30 16.0 0.80 (i) Calculate the percentage increase in the volume of gas produced from 10 °C to 15 °C. Give your answer to two significant figures. Space for working. …… % [3] (ii) Use the information in Table 2.1 to plot a line graph on the grid to show the effect of temperature on the rate of photosynthesis. [4] (iii) Describe the pattern shown by the data in your graph. …… [2] (iv) Use your graph to estimate the rate of photosynthesis when the temperature is 17 °C. Show on your graph where you took your readings. …… cm3 per minute [2] (c) Fig. 2.2 is a photograph of one flower of an aquatic plant, Cabomba caroliniana. Y X stigma magnification ×6 Fig. 2.2 (i) Make a large drawing of the flower shown in Fig. 2.2. Label the stigma on your drawing. [5] (ii) Measure the length of line XY on Fig. 2.2. length of line XY …… mm Calculate the actual width of the flower shown in Fig. 2.2 using your measurement and the formula. length of line XY on Fig. 2.2 magnification = actual width of the flower Include the unit. Space for working. [3] [Total: 23]