2025 CJC H2Bio PE P2 (QP)

NAME: ___________________________________________ CLASS: _________ INDEX: __________ CATHOLIC JUNIOR COLLEGE JC2 PRELIMINARY EXAMINATION Higher 2 BIOLOGY 9744/02 STRUCTURED QUESTIONS 01 Sept 2025 2 hours READ THESE INSTRUCTIONS FIRST Write your name (as per NRIC), class, and index number on all the work you hand in. Write in dark blue or black pen on both sides of the paper. [PILOT FRIXION ERASABLE PENS ARE NOT ALLOWED] You may use a soft pencil for any diagrams, graphs or rough working. Do not use staples, paper clips, highlighters, glue or correction fluid. The number of marks is given in brackets [ ] at the end of each question or part question. There are 11 questions with multiple subparts in this paper. Answer all questions in the spaces provided on the Question Paper. This document consists of 28 printed pages and 0 blank pages. [Turn over] For Examiner’s Use Total 100 1 2 3 4 5 6 7 8 9 10 11

2 9744 / 02 / Prelim Examination / 2025 Answer all questions 1 Fig. 1.1 shows ribosomes attached to the endoplasmic reticulum, carrying out protein synthesis. Fig. 1.1 (a) Name the structures labelled A to C ….……………………………………………………………………………………………………………...... ……..…………………………………………………………………………………………………………. [3] (b) With reference to Fig. 1.1, suggest the function of the protein that forms the membrane channel. ….……………………………………………………………………………………………………………...... ….……………………………………………………………………………………………………………...... ….……………………………………………………………………………………………………………...... ….……………………………………………………………………………………………………………...... ….……………………………………………………………………………………………………………...... ……..…………………………………………………………………………………………………………. [3]

3 9744 / 02 / Prelim Examination / 2025 (c) Proteins synthesised by ribosomes attached to the endoplasmic reticulum may be transported out of the cell. Explain the type of modification that occurs and the route taken. ….……………………………………………………………………………………………………………...... ….……………………………………………………………………………………………………………...... ….……………………………………………………………………………………………………………...... ….……………………………………………………………………………………………………………...... ….……………………………………………………………………………………………………………...... ……..…………………………………………………………………………………………………………. [3] (d) Suggest how prokaryotes, which have no endoplasmic reticulum or vesicles, are able to secrete proteins. ….……………………………………………………………………………………………………………...... ……..…………………………………………………………………………………………………………. [1] [Total: 10]

4 9744 / 02 / Prelim Examination / 2025 2 Fig. 2.1 shows two possible ways in which enzymes interact with their substrates. Fig. 2.1 (a) Explain the two roles of amino acids directly involved with enzyme action found at site P. ….……………………………………………………………………………………………………………...... ….……………………………………………………………………………………………………………...... ….……………………………………………………………………………………………………………...... ……..…………………………………………………………………………………………………………. [2] (b) Enzymes act with specificity and catalyse reactions. With reference to Fig. 2.1, explain how the two types of enzymes are able to do so. ….……………………………………………………………………………………………………………...... ….……………………………………………………………………………………………………………...... ….……………………………………………………………………………………………………………...... ……..…………………………………………………………………………………………………………. [2]

5 9744 / 02 / Prelim Examination / 2025 Acetyl-CoA carboxylase (ACC) is a four -subunit enzyme that regulates the synthesis of fatty acid by catalysing the conversion of acetyl -CoA to malonyl-CoA. ACC can also be allosterically activated by the action of another molecule, citrate. Fig. 2.2 shows the effect of the concentration of acetyl-CoA on ACC activity. Fig. 2.2 (c) Explain how ACC can be activated by citrate. ….……………………………………………………………………………………………………………...... ….……………………………………………………………………………………………………………...... ….……………………………………………………………………………………………………………...... ……..…………………………………………………………………………………………………………. [2] (d) On Fig. 2.2, draw and label the expected graph in the presence of citrate. ……..…………………………………………………………………………………………………………. [1]

6 9744 / 02 / Prelim Examination / 2025 (e) Biotin, also known as vitamin B, is attached to ACC for its proper functioning. Explain the role of biotin. ….……………………………………………………………………………………………………………...... ….……………………………………………………………………………………………………………...... ….……………………………………………………………………………………………………………...... ……..…………………………………………………………………………………………………………. [2] [Total: 9]

7 9744 / 02 / Prelim Examination / 2025 3 During interphase of the cell cycle, individual chromosomes cannot be seen within the nucleus. The genetic material is termed chromatin during this stage. (a) Changes occur to chromatin during mitosis so that chromosomes become visible. State what happens to chromatin so that individual chromosomes can be seen during mitosis. ….……………………………………………………………………………………………………………...... ……..…………………………………………………………………………………………………………. [1] (b) Fig. 3.1 is a transmission electron micrograph of two human chromosomes at metaphase of mitosis. Fig. 3.1 Describe the structure of chromosomes at metaphase, such as the two chromosomes in Fig. 3.1. ….……………………………………………………………………………………………………………...... …………………………………………………………………………………………………………………… ….……………………………………………………………………………………………………………...... ….……………………………………………………………………………………………………………...... …………………………………………………………………………………………………………………… ….……………………………………………………………………………………………………………...... ….……………………………………………………………………………………………………………...... ……..…………………………………………………………………………………………………………. [4]

8 9744 / 02 / Prelim Examination / 2025 (c) Yeasts are unicellular organisms from the kingdom Fungi. Saccharomyces cerevisiae is one species of yeast that can carry out either asexual reproduction by mitosis or sexual reproduction by meiosis. Budding in S. cerevisiae is a process where a small daughter cell forms as a bud on the parent cell. The bud contains a copy of the parent cell nucleus and it eventually separates from the parent cell to form a new cell. S. cerevisiae can exist in two forms: haploid cells or diploid cells. • Haploid cells can be one of two different mating types: a and α. • Haploid cells can only mate with other haploid cells of the opposite mating type. Fig. 3.2 shows the life cycle of S. cerevisiae with its asexual and sexual reproductive stages. Fig. 3.2

9 9744 / 02 / Prelim Examination / 2025 (i) With reference to Fig. 3.2, state the number(s) of the stages 1–5 that: involve mitosis .................... involve meiosis .................... [2] (ii) When there is a lack of nutrients, cells made in stage 3 will carry out stage 4 to make spores, which germinate only when conditions improve. Suggest and explain how the type of reproduction that makes spores during stage 4 is advantageous for S. cerevisiae in a changing environment. ….…………………………………………………………………………………………………………... ….…………………………………………………………………………………………………………... ….…………………………………………………………………………………………………………... ….…………………………………………………………………………………………………………... ….…………………………………………………………………………………………………………... ….………………………………………………………………………………………………………. [3] [Total: 10]

10 9744 / 02 / Prelim Examination / 2025 4 Transcription and translation are integral to gene expression. (a) Contrast between transcription and translation in eukaryotes. …………………………………………………………………………………………………………………… ………………………………………………………