AQA A LEVEL BIOLOGY Paper 1 MS 2021

Thursday 4 June 2020 Morning 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. For Examiner’s Use Question Mark 1 2 3 4 5 6 7 8 9 10 TOTAL Downloaded by: ibrahim03naqvi | Distribution of this document is illegal AQA A LEVEL BIOLOGY PAPER 1 MS 2021 S - The Marketplace for Revision Notes & Study Guides 2 Do not write outside the *02* IB/M/Jun20/7402/1 1 2 Answer all questions in the spaces provided. box 0 1 Figure 1 shows a cell from the lining of the ileum specialised for absorption of products of digestion. SGLT1 is a carrier protein found in the cell-surface membrane of this cell, it transports glucose and sodium ions (Na + ) into the cell. Figure 1 . The action of the carrier protein X in Figure 1 is linked to a membrane-bound ATP hydrolase enzyme. Explain the function of this ATP hydrolase. [2 marks] . The movement of Na + out of the cell allows the absorption of glucose into the cell lining the ileum. Explain how. [2 marks] 0 1 0 1 Downloaded by: ibrahim03naqvi | Distribution of this document is illegal S - The Marketplace for Revision Notes & Study Guides 3 Do not write outside the box *03* IB/M/Jun20/7402/1 0 1 . 3 Describe and explain two features you would expect to find in a cell specialised for absorption. [2 marks] 1 2 Question 1 continues on the next page Turn over ► Downloaded by: ibrahim03naqvi | Distribution of this document is illegal S - The Marketplace for Revision Notes & Study Guides 4 Do not write outside the *04* IB/M/Jun20/7402/1 box Figure 2 is a diagram of one SGLT1 carrier protein. Figure 2 0 1 . 4 Draw phospholipids on Figure 2 to show how the carrier protein, SGLT1, would fit into the cell-surface membrane. Do not draw more than eight phospholipids. [2 marks] Downloaded by: ibrahim03naqvi | Distribution of this document is illegal S - The Marketplace for Revision Notes & Study Guides 5 Do not write outside the *05* IB/M/Jun20/7402/1 5 10 . Figure 2 shows the SGLT1 polypeptide with NH2 at one end and COOH at the other end. Describe how amino acids join to form a polypeptide so there is always NH2 at one end and COOH at the other end. box You may use a diagram in your answer. [2 marks] Space for diagram: Turn over for the next question Turn over ► 0 1 Downloaded by: ibrahim03naqvi | Distribution of this document is illegal S - The Marketplace for Revision Notes & Study Guides 6 Do not write outside the *06* IB/M/Jun20/7402/1 1 To study lipid digestion, a scientist placed a tube into the gut of a healthy 20-year-old man. The end of the tube passed through the stomach but did not reach as far as the ileum. The scientist fed the man a meal containing triglycerides through the tube. The scientist also used the tube to remove samples from the man’s gut at intervals after the meal. The scientist measured the type of lipid found in the samples. Some of her results are shown in Table 1. Table 1 Sample Time of collection after meal / min Concentration of fatty acids / mg cm −3 Concentration of triglycerides / mg cm −3 A 45 2.7 0.6 B 75 3.3 0.0 . Use your knowledge of lipid digestion to explain the differences in the results for samples A and B shown in Table 1. box You should assume that no absorption had occurred. [3 marks] 0 2 0 2 Downloaded by: ibrahim03naqvi | Distribution of this document is illegal S - The Marketplace for Revision Notes & Study Guides 7 Do not write outside the IB/M/Jun20/7402/1 2 3 . After collecting the samples, the scientist immediately heated them to 70 °C for 10 minutes. Explain why. [2 marks] box . Describe the role of micelles in the absorption of fats into the cells lining the ileum. [3 marks] *07* Turn over ► 0 2 0 2 8 Downloaded by: ibrahim03naqvi | Distribution of this document is illegal S - The Marketplace for Revision Notes & Study Guides 8 Do not write outside the IB/M/Jun20/7402/1 1 box . At P on Figure 3, the pressure in the left ventricle is increasing. At this time, the rate of blood flow has not yet started to increase in the aorta. Use evidence from Figure 3 to explain why.