ACJC 2023 H2 Bio Prelim Paper 2 Questions

This document consists of 29 printed pages and 2 blank pages. [Turn over Anglo-Chinese Junior College JC2 Biology Preliminary Examination Higher 2 CANDIDATE NAME FORM CLASS TUTORIAL CLASS INDEX NUMBER BIOLOGY Paper 2 Structured Questions Candidates answer on the Question Paper. No Additional Materials are required. 9744/02 23 August 2023 2 hours READ THESE INSTRUCTIONS FIRST Write your Name, Class and Index number in the spaces at the top of this page. Write in dark blue or black pen. You may use an HB pencil for any diagrams or graphs. Do not use staples, paper clips, glue or correction fluid. Answer all questions in the spaces provided on the Question Paper. The use of an approved scientific calculator is expected, where appropriate. You may lose marks if you do not show your working or if you do not use appropriate units. The number of marks is given in brackets [ ] at the end of each question or part question. For Examiners’ use only 1 / 8 2 / 11 3 / 10 4 / 8 5 / 11 6 / 10 7 / 10 8 / 12 9 / 10 10 / 5 11 / 5 Total / 100

2 Anglo-Chinese Junior College 2023 J2 H2 9744 Paper 2 Preliminary Examination For Examiner Use Answer all questions. 1 The cell surface membranes of different cells have a similar basic structure, but the proportions of the various molecules present vary between membranes and even between the inner and outer layers of a membrane. Fig. 1.1 shows the structure of a typical cell surface membrane. Fig. 1.1 (a) With reference to Fig. 1.1, (i) identify molecules A and B and describe their respective functions. A …………………………………………………………………………………………............. Function ………………………………………………………………………………………… ………………………………………….…………………………………………………………. ………………………………………….…………………………………………………………. B …………………………………………………………………………………………............. Function ………………………………………………………………………………………… ………………………………………….…………………………………………………………. …………………………………………………………………………………………............ [4]

3 [Turn over Anglo-Chinese Junior College 2023 J2 H2 9744 Paper 2 Preliminary Examination For Examiner Use (ii) State one way in which the outer layer of the membrane is different from the inner layer. ………………………………………….…………………………………………………………. …………………………………………………………………………………………............ [1] (iii) Describe the significance of the difference stated in your answer for (a)(ii). ………………………………………….…………………………………………………………. …………………………………………………………………………………………............ [1] Fig. 1.2 shows an organelle which contains an extensive network of internal membranes. Fig. 1.2 (b) With reference to Fig. 1.1, suggest if molecule B will be found in the internal membranes found within the organelle shown in Fig. 1.2. Explain your answer. ……………………………………………….………………………………………………………….. ……………………………………………….………………………………………………………….. ……………………………………………….………………………………………………………….. ……………………………………………….………………………………………………………….. ……………………………………………………………………………………………………….. [2] [Total: 8]

4 Anglo-Chinese Junior College 2023 J2 H2 9744 Paper 2 Preliminary Examination For Examiner Use 2 One mechanism for bacterial resistance to antibiotics is through the action of efflux pumps, which are proteins found on the bacterial cell surface membrane. Table 2.1 shows the intracellular concentrations of an antibiotic in two strains of bacteria, after exposure to the antibiotic for 24 hours. Table 2.1 strain of bacteria intracellular concentration of antibiotic / mg L–1 antibiotic-resistant 0.008 antibiotic-susceptible 0.125 (a) Explain why antibiotics do not harm the human cells when used to treat humans. ……………………………………………….………………………………………………………….. ……………………………………………….………………………………………………………….. ……………………………………………….………………………………………………………….. ……………………………………………….………………………………………………………….. ……………………………………………………………………………………………………….. [2] (b) Describe how the efflux pumps are held in position within the membrane. ……………………………………………….………………………………………………………….. ……………………………………………….………………………………………………………….. ……………………………………………….………………………………………………………….. ……………………………………………….………………………………………………………….. ……………………………………………………………………………………………………….. [2]

5 [Turn over Anglo-Chinese Junior College 2023 J2 H2 9744 Paper 2 Preliminary Examination For Examiner Use (c) With reference to Table 2.1, explain how the presence of efflux pumps allow bacteria to be resistant to the antibiotic. ……………………………………………….………………………………………………………….. ……………………………………………….………………………………………………………….. ……………………………………………….………………………………………………………….. ……………………………………………….………………………………………………………….. ……………………………………………….………………………………………………………….. ……………………………………………….………………………………………………………….. ……………………………………………….………………………………………………………….. ……………………………………………….………………………………………………………….. ……………………………………………………………………………………………………….. [4] (d) Some strains of this bacteria show resistance to the antibiotic while other strains are susceptible, even though they both belong to the same species. Suggest explanations for this observation. ……………………………………………….………………………………………………………….. ……………………………………………….………………………………………………………….. ……………………………………………….………………………………………………………….. ……………………………………………….………………………………………………………….. ……………………………………………….………………………………………………………….. ……………………………………………….………………………………………………………….. ……………………………………………………………………………………………………….. [3] [Total: 11]

6 Anglo-Chinese Junior College 2023 J2 H2 9744 Paper 2 Preliminary Examination For Examiner Use 3 Fig. 3.1 shows models of a haemoglobin molecule and part of a keratin molecule. Fig. 3.1 (a) Outline the main structural differences between these two proteins, visible in Fig. 3.1. ……………………………………………….………………………………………………………….. ……………………………………………….………………………………………………………….. ……………………………………………….………………………………………………………….. ……………………………………………….………………………………………………………….. ……………………………………………….………………………………………………………….. ……………………………………………….………………………………………………………….. ……………………………………………………………………………………………………….. [3] (b) Describe the role of bonds in haemoglobin in increasing the efficiency of the loading and unloading of oxygen. ……………………………………………….………………………………………………………….. ……………………………………………….………………………………………………………….. ……………………………………………….………………………………………………………….. ……………………………………………….………………………………………………………….. ……………………………………………………………………………………………………….. [2]

7 [Turn over Anglo-Chinese Junior College 2023 J2 H2 9744 Paper 2 Preliminary Examination For Examiner Use BLANK PAGE

8 Anglo-Chinese Junior College 2023 J2 H2 9744 Paper 2 Preliminary Examination For Examiner Use Unlike haemoglobin which circulates in the blood, myoglobin is the oxygen-binding protein located primarily in muscles. Myoglobin serves as a local oxygen reservoir that can temporarily provide oxygen when blood oxygen delivery is insufficient. This happens during periods of intense muscular activity when the concentration of oxygen drops below 20 mm Hg. Fig. 3.2 shows the model of a myoglobin molecule.