AS BIOLOGY Paper 2

AS BIOLOGY Paper 2 Thursday 23 May 2024 Morning Time allowed: 1 hour 30 minutes Materials For this paper you must have: • a ruler with millimetre measurements • a scientific calculator. Instructions • Use black ink or black ball-point pen. • Fill in the boxes at the top of this page. • Answer all questions. • You must answer the questions in the spaces provided. Do not write outside the box around each page or on blank pages. • If you need extra space for your answer(s), use the lined pages at the end of this book. Write the question number against your answer(s). • Show all your working. • Do all rough work in this book. Cross through any work you do not want to be marked. Information • The marks for the questions are shown in brackets. • The maximum mark for this paper is 75. Answer all questions in the spaces provided. box 0 1 . 1 Water has a high heat capacity and a large latent heat of vaporisation. Describe the importance of each of these properties to living organisms. [2 marks] High heat capacity Large latent heat of vaporisation . Figure 1 shows that water loss from a porous pot can cause the upward movement of water. Figure 1 Biologists have concluded that the experiment in Figure 1 supports the cohesion–tension theory of water transport in the xylem. Explain how this conclusion is supported by the experiment in Figure 1. [3 marks] box Turn over ► box . A haemocytometer is a special microscope slide that can be used to determine the mean number of red blood cells in 0.004 mm3 of blood. • A researcher prepared a 10–3 dilution of a sample of blood from an adult. • Using a haemocytometer, the researcher determined that the mean number of red blood cells in 0.004 mm3 of the diluted blood sample was 21 The volume of blood in the body of the adult was 4.8 dm3 Calculate the total number of red blood cells in the body of this adult. box Show your working. [2 marks] Answer . The solution used to dilute the blood had to have the same water potential as the blood. Explain why. [2 marks] Question 2 continues on the next page Turn over ► . There are four main blood groups in the human ABO blood group system. Table 1 shows the basis on which each of these blood groups is classified. Table 1 ABO blood group Antigens present on red blood cells Antibodies present in blood plasma A A Anti-B B B Anti-A AB A and B No anti-A and no anti-B O No A and no B Anti-A and anti-B A transfusion of blood from a blood group A donor to a blood group B recipient would cause agglutination of the donated red blood cells. box Use information in Table 1 to explain why. [2 marks] . Using Table 1, give the blood groups of people who could accept a donation of blood group O without causing agglutination of the donated red blood cells. [1 mark] Blood groups . Describe how you would use cell fractionation and ultracentrifugation to obtain a sample of mitochondria from muscle tissue. box [4 marks] Question 3 continues on the next page *07* Turn over ► .