2025 TMJC H2Bio PE P3 (QP)

CANDIDATE NAME ( ) CIVICS GROUP H2 BIOLOGY 9744/03 Paper 3 Long Structured and Free-response Questions 22 September 2025 2 hours Candidates answer on the Question Paper. No additional materials are required. READ THESE INSTRUCTIONS FIRST Write your name and Civics Group in the spaces at the top of the 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. Section B Answer ONE question. 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. _________________________________________________________________________ This document consists of 27 printed pages and 3 blank pages. OVERALL Paper Score Weighting % 1 /30 15% % 2 /100 30% % 3 /75 35% % 4 /55 20% % TOTAL % GRADE For examiner’s Use Section A 1 / 28 2 / 12 3 / 10 Section B 4 or 5 / 25 Total / 75 TAMPINES MERIDIAN JUNIOR COLLEGE JC2 PRELIMINARY EXAMINATION

2 Tampines Meridian Junior College 2025 JC2 Preliminary Examinations H2 Biology Section A Answer all questions in this section. 1 Adult stem cells are undifferentiated cells that are found in most animal tissues. Adult stem cells can divide throughout their lifespan to form identical stem cells (self-renewal) or to form cells that can differentiate into the functioning cells of that tissue. (a) Uncontrolled cell division is a characteristic feature of tumour formation from a differentiated cell. (i) Describe two other features of tumour formation from a fully differentiated cell. [2] ………………………………………………………………………………………………. ………………………………………………………………………………………………. ………………………………………………………………………………………………. ………………………………………………………………………………………………. ………………………………………………………………………………………………. Telomeres are non-coding DNA found at the end of the chromosomes. Adult stem cells have chromosomes with long telomeres. (ii) Explain why having long telomeres is an advantage to cells that are undergoing many rounds of cell cycles. [2] ………………………………………………………………………………………………. ………………………………………………………………………………………………. ………………………………………………………………………………………………. ………………………………………………………………………………………………. ……………………………………………………………………………………………….

3 Tampines Meridian Junior College 2025 JC2 Preliminary Examinations H2 Biology (b) Haematopoietic stem cells (HSCs), also called blood stem cells, are adult stem cells that are located in the bone marrow. HSCs have a role in the formation of blood cells. Fig. 1.1 is an outline showing the formation of some of the different types of blood cell that can be formed from HSCs. The first stage is the division of HSCs to produce myeloid and lymphoid stem cells. Fig. 1.1 With reference to Fig 1.1, explain why GMP cells cannot be described as haematopoietic stem cells (HSCs). [2] ……….....……………………………………………………………………………………………. ……….....……………………………………………………………………………………………. ……….....……………………………………………………………………………………………. ..….....…………………………………………………………………………………………….…. ..….....…………………………………………………………………………………………….….

4 Tampines Meridian Junior College 2025 JC2 Preliminary Examinations H2 Biology (c) The differentiation of T‑lymphocytes begins in the bone marrow and continues in an organ known as the thymus to produce fully differentiated T‑helper and T-cytotoxic cells. In the thymus, T‑lymphocytes that bind to self-antigens are destroyed. (i) Suggest why T‑lymphocytes that bind to self-antigens need to be destroyed in the thymus. [3] ………………………………………………………………………………………………. ………………………………………………………………………………………………. ………………………………………………………………………………………………. ………………………………………………………………………………………………. ………………………………………………………………………………………………. ………………………………………………………………………………………………. ……………………………………………………………………………………………….

5 Tampines Meridian Junior College 2025 JC2 Preliminary Examinations H2 Biology BLANK PAGE

6 Tampines Meridian Junior College 2025 JC2 Preliminary Examinations H2 Biology Mature T-lymphocytes leave the thymus gland to travel throughout the body. They remain inactive inside organs, such as the spleen and lymph nodes, until activated by the presence of foreign antigens. Fig. 1.2 shows what happens to two mature T -lymphocytes, U1 and V1, in the presence of an antigen from a virus. Fig. 1.2

7 Tampines Meridian Junior College 2025 JC2 Preliminary Examinations H2 Biology (ii) U4 and V4 are two types of mature T-lymphocyte. Identify the names given to these types of T -lymphocytes by putting a ( ✓) beside the correct box. [1] types of mature T-lymphocytes U4 V4 T-cytotoxic cells T-helper cells (iii) Describe the roles of V4 in an adaptive immune response. [2] ………………………………………………………………………………………………. ………………………………………………………………………………………………. ………………………………………………………………………………………………. ………………………………………………………………………………………………. ………………………………………………………………………………………………. (d) T-helper cells play a crucial role in orchestrating the immune response against various pathogens. However, they are also the primary target of the human immunodeficiency virus (HIV), a retrovirus, which contains the enzyme reverse transcriptase. HIV infects and destroys T-helper cells, gradually reducing their numbers. This weakens the immune system, making individuals susceptible to opportunistic infections and cancers. Explain why HIV is described as a retrovirus. [2] ……….………………………………………………………………………………………………. ……….………………………………………………………………………………………………. ……….………………………………………………………………………………………………. ……….………………………………………………………………………………………………. ……….……………………………………………………………………………………………….

8 Tampines Meridian Junior College 2025 JC2 Preliminary Examinations H2 Biology (e) In people with HIV/AIDs, a serious lung disease known as pneumocystis pneumonia can result from infection by an opportunistic pathogen known as Pneumocystis jirovecii. Although the cells of many species of bacteria are the same size as those of P . jirovecii, research concluded that the organism is a eukaryote and is not a bacterium. In 1988, analysis of ribosomal RNA (rRNA) resulted in P . jirovecii being classified as a fungus. Studies o n the structure of P . jirovecii have identified that the cell wall is made of polysaccharides such as chitin and 1,3‑β‑D‑glucan. (i) Explain why this feature helped scientists to confirm that P . jirovecii is not a bacterium. [1] ………………………………………………………………………………………………. ………………………………………………………………………………………………. ………………………………………………………………………………………………. (ii) Scientists have identified other features of the cell structure of P. jirovecii. Some of these are listed in Table 1.1. Complete each row of Table 1.1 so that the table shows: [2] • four structural features identified in P. jirovecii • one function for each structural feature • whether the structural feature present in P . jirovecii is also present ( ✓) or is absent (✗) in bacterial cells. Table 1.1 structural feature of P. jirovecii function present (✓) or absent (✗) in bacterial cells ribosomes protein synthesis smooth endoplasmic reticulum Golgi body modification of proteins and lipids aerobic respiration

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