2022 TJC JC2 H2 Biology Prelim P3 ANS

1 [TURN OVER READ THESE INSTRUCTIONS FIRST Write your Center number, index number and name 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. DO NOT WRITE IN ANY BARCODES. Section A Answer all questions in the spaces provided on the Question Paper. Section B Answer any one question in 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 any working 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. TEMASEK JUNIOR COLLEGE 2022 JC2 PRELIMINARY EXAMINATION Higher 2 CANDIDATE NAME CENTRE NUMBER S INDEX NUMBER BIOLOGY 9744/03 Paper 3 Long Structured and Free Response Questions PART I 13 SEPTEMBER 2022 2 hours Candidates answer on the Question Paper. No Additional Materials are required. For Examiner’s Use 1 / 9 2 / 17 3 / 24 4 / 5 / 25 This document consists of 9 printed pages and 3 blank pages.

2 Section A Answer all questions in this section. 1 To investigate other conditions affecting rate of photosynthesis, two sets of plants, A and B, were grown from seeds at different concentrations of carbon dioxide: • A – normal atmospheric concentration of carbon dioxide (0.033%) • B – twice the normal atmospheric concentration of carbon dioxide (0.066%) The rates of photosynthesis at different light intensities for the two sets of plants were measured and shown in Fig. 1.1. Fig. 1.1 (a) With reference to Fig. 1.1, (i) describe and explain, in terms of limiting factors, the results from the plants in set A; [2] 1. QF: As light intensity increases from 0.5 to 6 a.u., mean rate of photosynthesis increases from 0 a.u. to 1.9 a.u. A: 5.4 – 7 a.u. for upper limit with correct y-axis values quoted 2. light intensity is main limiting factor 3. QF: As light intensity increases from 6 a.u. to 10 a.u., mean rate of photosynthesis remains constant / levels off / reaches plateau at 2 a.u. A: Continue from point 1 QF 4. Light intensity is not limiting, CO2 concentration is limiting Note: many students missed out the word “concentration” – the phrase “carbon dioxide is limiting” is not accurate - ½ if student used (a.u.) without abbreviating at the start of the answer since question did not abbreviate light intensity / arbitrary units mean rate of photosynthesis per unit area of leaf / arbitrary units

3 [TURN OVER Marker’s comments: Some students are still using phrases such as “increase at a fast rate / slow rate” – LAST REMINDER to avoid using the word RATE to describe a graph (unless it’s the title of the axis) Some students also gave unnecessary details such as WHY light intensity affects rate of photosynthesis – look at the number of marks to guide you in deciding how much details to include in your answer. (ii) explain the difference between the results of set A and set B at high light intensities. [2] 1. QF: Twice as much carbon dioxide in set B than set A 2. Higher rate of carbon fixation 3. During Calvin cycle 4. QF: CO2 concentration is limiting in set A at high light intensities from 6 a.u. onwards while CO2 concentration (A: temperature) will be limiting in set B at light intensity from 9.6 a.u. (A: 9.8, 10) Idea: Another factor becomes limiting when the rate of photosynthesis plateaus with QF

4 (b) Fig. 1.2 is a graph showing the estimated area of trees that have been removed from tropical forests between 2001 and 2017. Fig. 1.2 (i) State the year which had the lowest estimated area of trees removed from t ropical forests on Fig. 1.2. [1] 2003 (ii) State the area of trees removed in 2012 on Fig. 1.2. [1] 110 000 km2 (Note: 0 marks if no units)

5 [TURN OVER (iii) A student made three statements about the data in Fig. 1.2: 1 The number of trees cut down increases every year. 2 The number of trees cut down in 2014 was three times more than the number of trees cut down in 2003. 3 Fewer trees were cut down in 2017 than in 2016. Complete Table 1.1 by using the data in Fig. 1.2 to decide if each statement is true or false and state the evidence that supports your decision. Table 1.1 statement true or false evidence from Fig. 1.2 1 false Decreases in 2002 / 2005 / 2007 / 2010 / 2012 / 2014 / 2016 or No increase in 2004 or Although the general trend shows an increase, it does not increase every year / some years increase and some years decrease 2 false 65 000 km2 were cut down in 2003 and 121 000 km2 in 2014 which is less than three times or three times more would be 195 000 km2 which is more than the number cut down in 2014 or 1.86 times (not 3 times) the number were cut down 3 true more trees were cut down in 2016 than in 2017 or 170 000 km2 trees were cut down in 2016 and 158 000 km2 were cut down in 2016 Max [1] – if no evidence stated for all 3 statements but T/F correct Ecf [1/2] if T/F wrong but evidence supports Ecf [1/2] if T/F correct but evidence not clear -1/2 m if QF wrong [3]

6 [Total: 9] 2 Hepatitis is the inflammation of the liver and can be caused by a number of different hepatitis viruses. Presently, the only effective vaccines available are for hepatitis A and B. (a) Outline the immune response that leads to the production of antibodies after vaccination. [3] 1. Vaccine contains hepatitis antigen / attenuated hepatitis virus 2. APC / macrophage phagocytose and present hepatitis antigen from vaccine to specific naive CD4 T cells and naive B cells Note: it MUST be clear that the antigen is presented in this part of the answer. No marks awarded if it is mentioned that T/B cell receptor recognize and bind to antigen because it is not clear that the antigen was presented in this step. 3. Naive CD4 T cells activated, which proliferate and differentiate to form helper T and memory T cells. 4. Helper T cells secrete cytokines 5. Completes activation of naïve B cells to proliferate and differentiate into plasma cells and memory B cells. 6. Plasma B cells produce antibodies specific to hepatitis antigen 7. Vaccination trigger active immunity / active immune response General comments: Differentiate between use of ‘pathogen’ and ‘antigen’. Be specific – use the context to add specificity! A handful of students misinterpreted the question and described secondary immune response instead. (b) Briefly describe how plasma cells produce and release antibodies. [4] 1. Transcription of light and heavy chain gene produces pre-mRNA 2. Pre-mRNA processing take place. 3. Ribosomes on rER translate mRNA 4. Heavy and light chains of antibodies move into rER lumen. (A: if heavy and light chain mentioned later in answer) (R: polypeptide chain IF “light and heavy chain gene” mentioned in MP1) (ECF: polypeptide chain IF “light and heavy chain gene” not mentioned in MP1) 5. These are enclosed in ER/ transport vesicle which pinch / bud off from ER 6. to cis face of Golgi apparatus (GA). 7. Heavy and light chains are joined by disulfide bonds and glycosylated / addition of carbohydrate side chain as they move through the GA (R: chemical modification only) 8. The secretory vesicle buds off from trans-face of GA, fuse with the plasma membrane. Thus, releasing the antibodies out of the cell via exocytosis. [1/2] – mention of light chain and heavy chain gene (if wrong focus)

7 [TURN OVER