A-level BIOLOGY Paper 1

A-level BIOLOGY Paper 1 Wednesday 5 June 2024 Afternoon Time allowed: 2 hours 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 91. Answer all questions in the spaces provided. box 0 1 . 1 Figure 1 shows the structure of a fatty acid molecule and the structure of a glycerol molecule. Figure 1 On Figure 1, draw a circle around the part of the fatty acid molecule and the part of the glycerol molecule that is removed to form a bond in a triglyceride molecule. Name the bond formed between a fatty acid and glycerol in a triglyceride molecule. Name the reaction involved in forming a bond between a fatty acid and glycerol in a triglyceride molecule. [3 marks] Bond Reaction box . Name the fatty acid shown in Table 1 that is a saturated fatty acid. [1 mark] . The melting point is the temperature at which a solid changes state to be a liquid. Use Table 1 to describe the relationship between fatty acid structure and fatty acid melting point. [1 mark] Question 1 continues on the next page Turn over ► . The ratio of saturated to unsaturated fatty acids in a cell-surface membrane determines the extent of the membrane’s fluidity. Scientists provided a cell culture of mouse phagocytes with liquid broth rich in unsaturated fatty acids. The scientists observed: • an increase in the proportion of phospholipids in the phagocytes containing unsaturated fatty acids • more phagocytosis. box Suggest and explain why there was more phagocytosis. [3 marks] box . What are microvilli? [1 mark] Question 2 continues on the next page Turn over ► . Vitamin A is a fat-soluble substance. Micelles are involved in the process of vitamin A absorption. Describe the process of vitamin A absorption into cells lining the ileum. [3 marks] box Turn over for the next question DO NOT WRITE ON THIS PAGE ANSWER IN THE SPACES PROVIDED box *07* Turn over ► . Describe how we breathe in. [3 marks] box . A scientist prepared alveolar tissue to view using an optical microscope. The scientist cut very thin slices of the alveolar tissue. Explain why the scientist used very thin slices of alveolar tissue with the optical microscope. [2 marks] *0* . Figure 2 is an image of the lung tissue observed using an optical microscope. Figure 2 box Identify the tube labelled A. [1 mark] A The scientist used a ruler to measure the diameter of some of the alveoli. Table 2 shows the scientist’s results. Table 2 Alveolus diameter / mm Alveolus diameter / mm 4 2 5 1 2 3 5 2 0 3 . 4 The magnification of the image in Figure 2 is × 40 Use this information and Table 2 to calculate the mean diameter, in μm, of the alveoli. Show your working. [2 marks] Answer μm Turn over ► Percentage error