TMJC 2023 H2 P3 QP

CANDIDATE NAME CIVICS GROUP H2 BIOLOGY 9744/03 Paper 3 Long Structured and Free-response Questions 18 September 2023 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 19 printed pages and 1 blank page. For examiner’s Use Section A 1 / 30 2 / 20 Section B 3 or 4 / 25 Total / 75 TAMPINES MERIDIAN JUNIOR COLLEGE JC2 PRELIMINARY EXAMINATION

2 Tampines Meridian Junior College 2023 JC2 Preliminary Examination H2 Biology Section A Answer all questions in this section. 1 (a) The pituitary gland is located in the brain of mammals. Prolactin, a hormone from the pituitary gland, stimulates cells in the mammary glands of female mammals so that the cells are able to secrete milk. (i) State the potency of the stem cells that produce pituitary cells. [1] ..………………………………………………………………………………………………… (ii) With reference to the information provided, explain how the stem cells in pituitary gland stimulate cells in the mammary gland to secrete milk. [3] ..………………………………………………………………………………………………… .…………………………………………………………………………………………………. .…………………………………………………………………………………………………. ………………………………………………………………………………………………….. .…………………………………………………………………………………………………. ………………………………………………………………………………………………….. .…………………………………………………………………………………………………. (iii) Cells in the mammary glands that have been stimulated by prolactin need more glucose. State one reason why those cells need more glucose. [1] ………………………………………………………………………………………………….. .………………………………………………………………………………………………….

3 Tampines Meridian Junior College 2023 JC2 Preliminary Examination H2 Biology (b) Female mammals produce milk to feed new-born offspring. Secretory Immunoglobulin A (SIgA) is the main antibody found in breast milk of humans. It is secreted from IgA-producing plasma cells into cavities within the mammary glands to form milk with other components. (i) Explain how newly synthesi sed SIgA in the IgA -producing plasma cells reach the cavities within the mammary glands. [4] ………………………………………………………………………………………………….. .…………………………………………………………………………………………………. ………………………………………………………………………………………………….. .…………………………………………………………………………………………………. ………………………………………………………………………………………………….. .…………………………………………………………………………………………………. ………………………………………………………………………………………………….. .…………………………………………………………………………………………………. ………………………………………………………………………………………………….. (ii) The antibodies and other components in the breast milk provide immediate protection to newborns in fighting infections. However, this is not a long-term protection. Explain why antibodies such as SIgA in breast milk will not produce long-term protection to newborns. [2] ………………………………………………………………………………………………….. .…………………………………………………………………………………………………. ………………………………………………………………………………………………….. .…………………………………………………………………………………………………. .………………………………………………………………………………………………….

4 Tampines Meridian Junior College 2023 JC2 Preliminary Examination H2 Biology (c) β-catenin signal ling pathway involving WNT as a ligand is important in regulating cell proliferation during mammary gland development. When WNT binds to the Frizzled receptor embedded on the cell surface membrane, β -catenin is activated which translocates into the nucleus to upregulate the transcription of target genes. Fig. 1.1 shows the signalling pathway with and without WNT. Fig. 1.1 (i) The shape of Frizzled receptor is characteristic of a particular group of transmembrane receptor proteins. Name this group of proteins. [1] …………………………………………………………………………………………………..

5 Tampines Meridian Junior College 2023 JC2 Preliminary Examination H2 Biology (ii) Suggest how β-catenin is degraded in the absence of WNT. [2] ………………………………………………………………………………………………….. .…………………………………………………………………………………………………. ………………………………………………………………………………………………….. .…………………………………………………………………………………………………. ………………………………………………………………………………………………….. (iii) Cell surface membrane is made up of phospholipid molecules. Explain why triglycerides are not suitable as a component of cell surface membranes. [2] ………………………………………………………………………………………………….. .…………………………………………………………………………………………………. ………………………………………………………………………………………………….. .…………………………………………………………………………………………………. …………………………………………………………………………………………………..

6 Tampines Meridian Junior College 2023 JC2 Preliminary Examination H2 Biology (d) One of the target genes in WNT /β-catenin signalling pathway is cyclin D1 gene. Fig. 1.2 shows the percentage of β-catenin activity and cyclin D1 protein level during the mitotic cell cycle of a mammary gland cell. Fig. 1.2 With reference to Fig.1.1 and Fig.1.2, describe and explain the effect of β-catenin on cyclin D1 gene expression from G1 to S and mitosis of mammary gland cell. [4] ……………………………………………………………………………………………………….. ……………………………………………………………………………………………………….. ……………………………………………………………………………………………………….. ……………………………………………………………………………………………………….. ……………………………………………………………………………………………………….. ……………………………………………………………………………………………………….. ……………………………………………………………………………………………………….. ……………………………………………………………………………………………………….. ………………………………………………………………………………………………………..

7 Tampines Meridian Junior College 2023 JC2 Preliminary Examination H2 Biology (e) The dysregulation of the β-catenin signalling pathway is frequently linked to breast cancer. A young scientist conducted an experiment to compare the amount of β-catenin protein in breast cancer cells and normal cells to determine if β-catenin gene expression is high in breast cancer. (i) Explain why the amount of β-c atenin protein is used as an indicator of breast cancer rather than the amount of β-catenin DNA. [2] …………………………………………………………………………………………………… .………………………………………………………………………………………………….. (ii) β-catenin is encoded by the CTNNB1 gene. While CTNNB1 mutations are rare in breast cancer, they are found in many other types of cancer. Table 1.1 displays a mutation that is often seen in CTNNB1. Table 1.1 Name of mutation Change in DNA Change in β-catenin Nucleotide present in CTNNB1 Nucleotide present after mutation Amino acid before mutation Amino acid after mutation K354T Adenine (A) Cytosine (C) Lysine (Lys) Threonine (Thr) With reference to Table 1.1, explain the meaning of a gene mutation. [2] …………………………………………………………………………………………………… .………………………………………………………………………………………………….. …………………………………………………………………………………………………… .………………………………………………………………………………………………….. ……………………………………………………………………………………………………

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