NJC 2023 H2 Biology Prelim P3 QP

©NJC 2023 9744/03/SH2/H2/Biology/Preliminary Examination [Turn over NATIONAL JUNIOR COLLEGE, SINGAPORE Senior High 2 Preliminary Examination Higher 2 CANDIDATE NAME BIOLOGY CLASS 2bi2___ REGISTRATION NUMBER BIOLOGY Paper 3: Long Structured and Free-response Questions Candidates answer on the Question Paper and Answer Booklet No Additional Materials are required. 9744/03 25 August 2023 2 hours READ THESE INSTRUCTIONS FIRST Write your name and Biology class 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. Section A Answer all questions in the spaces provided on the Question Paper. Section B Answer any one question in the Answer Booklet. The use of an approved scientific calculator is expected, where appropriate. You may lose marks if you do not show your workings or if you do not use appropriate units. The number of marks is given in the brackets [ ] at the end of each question or part question. For Examiner’s Use Section A 1 /30 2 /10 3 /10 Section B 4/5 /25 Total /75 This document consists of 14 printed pages and 2 blank pages.

2 ©NJC 2023 9744/03/SH2/H2/Biology/Preliminary Examination Section A Answer all the questions in this section. 1 FoxO1 is a protein found in pancreatic β cells. Fig.1.1 shows a model of FoxO1. Fig. 1.1 (a) Describe how monomers may be linked together to form the FoxO1 polypeptide chain. Make bottom border for writing. [2] (b) Explain how amino acids that are spaced far apart in the Fox O1 polypeptide chain may be brought together in its 3-dimensional structure. [4]

3 ©NJC 2023 9744/03/SH2/H2/Biology/Preliminary Examination [Turn over Diabetes is often associated with the failure of the β (beta) cells in the pancreas, but it is unclear what actually causes this failure. Some studies have suggested that this failure may be related to FoxO1. A study was conducted using mice lacking the gene for FoxO1 in β cells (IKO) as well as normal (control) mice. Blood glucose levels after fasting were compared for four groups of mice: young (3 months old) male mice, young (3 months old) female mice, older females (who have had several pregnancies) and aging males (16–20 months). The results are shows in Fig. 1.2. Fig. 1.2 (c) Describe and explain the blood glucose levels after fasting between young control mice and young IKO mice without FoxO1. [3]

4 ©NJC 2023 9744/03/SH2/H2/Biology/Preliminary Examination (d) Aging and having pregnancies are considered to be physiological stresses. Describe and explain the effect of stress on blood glucose levels in control mice. Make bottom border for writing. [3] (e) Insulin and glucagon are hormones that are synthesi sed by pancreatic cells and secreted into the bloodstream in response to changes in blood glucose concentration to maintain homeostasis. Explain how such newly synthesi sed hormones are processed and released into the bloodstream by pancreatic cells. Make bottom border for writing. [4]

5 ©NJC 2023 9744/03/SH2/H2/Biology/Preliminary Examination [Turn over The levels of pancreatic hormones and β cell mass in older female control mice and older female IKO mice lacking FoxO1 were then investigated. The results are shown in Fig. 1.3. Fig. 1.3 (f) Calculate the percentage difference in β cell mass of the IKO mice compared to the control mice. Show your workings and give your answer in three significant figures. 2 % [2]

6 ©NJC 2023 9744/03/SH2/H2/Biology/Preliminary Examination (g) Outline the relationship between lack of FoxO1 and levels of pancreatic hormones in mice. Make bottom border for writing. [2] (h) Using information from Fig. 1.2 and Fig. 1.3, deduce the relative levels of pancreatic hormones in young female control and IKO mice lacking FoxO1 Make bottom border for writing. [1] To examine whether the changes observed were due to lack of β cell function or change in β cell number, investigators studied the following types of cells: • still producing insulin • newly formed β cells • no longer producing insulin. The results are shown in Fig. 1.4.

7 ©NJC 2023 9744/03/SH2/H2/Biology/Preliminary Examination [Turn over Fig. 1.4 (i) State which group of cells showed the least change in the mice studied. [1] (i) Describe the effects of aging on the distribution of cell types in mice. Make bottom border for writing. [3] (j) A hypothesis has been suggested that diabetes is caused by β cells losing their function, not by their death. Discuss the extent to which the data in Fig. 1.3 and Fig 1.4 support this hypothesis. [3]

8 ©NJC 2023 9744/03/SH2/H2/Biology/Preliminary Examination (k) When there are high blood glucose levels, more FoxO1 is found in the nucleus of the cell than in the cytoplasm. Based on all the information provided, suggest a role for FoxO1. [2] [Total: 30]

9 ©NJC 2023 9744/03/SH2/H2/Biology/Preliminary Examination [Turn over 2 The HIV/AIDS epidemic in the 2000s has had a very large impact on life expectancy in many African countries. Table 2.1 shows estimated data for four African countries for: • the average life expectancy of an individual born in 2002 • the average life expectancy of an individual born in 2002 if there was no HIV/ AIDS pandemic • the percentage of the population testing positive for HIV in 2002. Table 2.1 Country Life expectancy / years Percentage of population testing positive for HIV Without HIV/AIDS With HIV/AIDS Kenya 65.6 45.5 14.0 Malawi 56.3 38.5 16.0 South Africa 66.3 48.8 19.9 Zambia 55.4 35.3 20.0 (a) Using the data shown in Table 2.1, calculate the percentage decrease in life expectancy for Zambia due to HIV/AIDS. Show your workings and give your answer to the nearest whole number. % [2]

10 ©NJC 2023 9744/03/SH2/H2/Biology/Preliminary Examination (b) Evaluate if there is a correlation between the percentage of the population testing positive for HIV and percentage decrease in estimated life expectancy with HIV/AIDS. [3] (c) Explain the role gp120 and gp41 in the reproductive cycle of HIV. [2] (d) Following infection, CD4+ T cells will synthesise new copies of gp120 and gp41. Explain how cellular synthesis of gp120 and gp41 can lead to the destruction of infected CD4+ T cells by the immune system. [3] [Total: 10]