2025 VJC H2 Biology Prelim P2

1 VICTORIA JUNIOR COLLEGE JC 2 PRELIMINARY EXAMINATION 2025 HIGHER 2 NAME : ……………………………………………………….………………. CT CLASS: ………………...……… BIOLOGY Paper 2 Structured Questions 9744 / 02 16/09/2025 2 hour Candidates answer on the Question Paper. No Additional Materials are required. READ THESE INSTRUCTIONS FIRST Write your name and CT 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. Answer all questions in the spaces provided on the Question Paper. 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 bracket [ ] at the end of each question or part question. Question Marks 1 2 3 4 5 6 7 8 9 10 11 Total This document consists of 28 printed pages. [Turn over]

2 Answer all questions. 1 In most cell types, ribosomes are the most abundant organelles by number. They are present in both prokaryotic and eukaryotic cells, although their sizes and structures differ. (a) (i) State one structural feature of ribosomes that is common to both prokaryot ic and eukaryotic cells. …………………………………………………………………………………………………... ……………………………………………………………………………………………..… [1] (ii) Suggest how the difference in ribosome size between prokaryotic and eukaryotic cells can be exploited in medicine. …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... ……………………………………………………………………………………………..… [2]

3 (b) Unlike prokaryotic and eukaryotic cells, viruses such as SARS -CoV-2 lack ribosomes entirely. Fig. 1.1 shows the structure of the SARS-CoV-2. Fig. 1.1 With reference to the information provided, (i) explain how the structural features of SARS-CoV-2 show that it does not fully conform to the cell theory. …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... ……………………………………………………………………………………………..… [2] (ii) compare the genetic material between SARS-CoV-2 and prokaryotic cells. …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... ……………………………………………………………………………………………..… [3] [Total: 8]

4 2 Proteins are large macromolecules that comprise one or more long chains of amino acid residues. A linear chain of amino acid residues is known as a polypeptide. A polypeptide is formed by ribosomes in a process called translation, in which amino acids are added to an elongating polypeptide sequentially. Collagen is an example of a protein with a quaternary structure. It is the main structural protein in the extracellular matrix of the connective tissues of many animals. It is the most abundant protein in mammals, making up 25– 35% of protein content. It is mostly found in cartilage, bones, tendons, ligaments, and skin. Vitamin C is viral for collagen synthesis. Fig. 2.1 shows the general structure of an amino acid. Fig. 2.1 (a) (i) Draw a circle in Fig. 2.1 to indicate the part of the amino acid that is bonded to the elongating polypeptide. [1] (ii) Draw a labelled diagram in the space provided below to show how a dipeptide is formed. [3]

5 (b) Other than peptide bonds, other bonds are also found in collagen. These bonds function to maintain the structure of collagen. Describe how these bonds help to maintain the quaternary structure of collagen. ………………………………………………………………………………………………………. ………………………………………………………………………………………………………. ………………………………………………………………………………………………………. ………………………………………………………………………………………………………. ………………………………………………………………………………………………………. ………………………………………………………………………………………………………. ………………………………………………………………………………………………………. …………………………………………………………………………………………………… [4] (c) In recent years, collagen hotpot has been gaining popularity among diners. Unlike other hotpots, collagen hotpot contains an additional ingredient, with lumps of beige- coloured collagen jelly melted into the soup. Available at food courts and restaurants in Singapore, it has been attracting patrons, who hope that the soup would give their skin a lift while tantalising their taste buds. However, most health experts are sceptical about the claim that such collagen- infused hotpots help to increase the amount of collagen in our bodies. Using your knowledge of collagen, suggest two reasons for the scepticism of the health experts. ………………………………………………………………………………………………………. ………………………………………………………………………………………………………. ………………………………………………………………………………………………………. …………………………………………………………………………………………………… [2] [Total: 10]

6 3 Cellulase is an enzyme produced in plants where it hydrolyses cellulose in the cell walls, playing a role in processes such as fruit ripening and leaf abscission. Fig. 3.1 shows the effect of temperature on the activity of cellulase in ripening fruits of Musa acuminata (banana) and Mangifera indica (mango). Fig. 3.1 (a) (i) With reference to Fig. 3.1, compare the effects of temperature on cellulase in ripening fruits of banana and mango. …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... ……………………………………………………………………………………………..… [3]

7 (ii) With reference to the types of bonding in proteins, suggest how differences in the tertiary structure of cellulase in ripening fruits of banana and mango could explain the differences in their activities shown in Fig. 3.1. …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... ……………………………………………………………………………………………..… [3]

8 (b) Juices extracted commercially from fruits can be made less cloudy by the breakdown of the cell wall using the enzymes cellulase, pectinase and xylanase: • pectinase hydrolyses pectin • xylanase hydrolyses hemicellulose. An investigation was carried out into the effect of ultrasound on the activity of cellulase, pectinase and xylanase used in fruit juice manufacture. For each enzyme, the effect of ultrasound was compared with no ultrasound on the: • maximum rate of reaction (Vmax) • Michaelis-Menten constant (Km) • catalytic efficiency (Vmax / Km) Table 3.1 summarises the results. A higher Vmax / Km indicates higher catalytic efficiency. Table 3.1 enzyme method comparison of Vmax comparison of Km Vmax / Km / min-1 cellulase ultrasound higher higher 34 no ultrasound lower lower 29 pectinase ultrasound same lower 945 no ultrasound same higher 759 xylanase ultrasound higher same 146 no ultrasound lower same 125 (i) With reference to the information in Table 3.1, explain why ultrasound results in higher catalytic efficiency in the hydrolysis of pectin. …………………………………………………