2024 ASRJC H2 Bio P2 QP

ASRJC BIOLOGY DEPT 9744//2024/J2PRELIM/P2 [Turn over H2 ANDERSON SERANGOON JUNIOR COLLEGE HIGHER 2 2024 JC2 PRELIMINARY EXAMINATIONS CANDIDATE NAME CLASS INDEX NUMBER BIOLOGY 9744/02 PAPER 2 SHORT STRUCTURED QUESTIONS Candidates answer on the Question Paper. No Additional Materials are required. 12 SEPTEMBER 2024 THURSDAY 2 HOURS READ THESE INSTRUCTIONS FIRST Write your name and class on all the work you hand in. Write in dark blue or black pen. You may use an HB pencil for any diagrams or graph Do not use paper clips, highlighters, glue or correction fluid. Answer all questions. 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. At the end of the examination, fasten all your work securely together. The number of marks is given in brackets [ ] at the end of each question or part question. This document consists of 35 printed pages and 1 blank page For Examiner’s Use 1 / 7 2 / 10 3 / 11 4 / 11 5 / 12 6 / 10 7 / 10 8 / 8 9 / 12 10 / 4 11 / 5 Total /100

2 ASRJC BIOLOGY DEPT 9744//2024/J2PRELIM//P2 Answer all the questions. 1 Starch and cellulose are carbohydrates that are found in most plants. (a) Compare between the structures of amylose and amylopectin of starch. …………………………………………………………………………………………...……... ………………………………………………………………………………………………….. …………………………………………………………………………………………...……... ………………………………………………………………………………………………….. [2] (b) Juices that are extracted commercially from fruits can be made less cloudy by the breakdown of the cellulose cell wall using the enzyme cellulase. In the space below, show how the bonds in a short section of cellulose that is made up of three monomers may be broken by cellulase. Add appropriate labels to your drawing. [3]

3 ASRJC BIOLOGY DEPT 9744//2024/J2PRELIM/P2 [Turn over (c) Fig. 1.1 is an electron micrograph showing parts of two plant cells. The middle lamella is a layer, composed largely of a polysaccharide known as pectin, that cements together the cell wall of two adjacent plant cells. Pectins can also be found in the cell wall of plant cells. Fig 1.1 Fig. 1.2 shows a diagrammatic representation of the complex structure of the plant cell wall. Pectins are hydrophilic structures and interact with both cellulose and cross - linking glycans to hold cell walls close together. Glycans are carbohydrate molecules. Fig. 1.2 With reference to Fig. 1.2, suggest how the structure of the cell wall facilitates the passage of water between plant cells. …………………………………………………………………………………………...……... ………………………………………………………………………………………………….. …………………………………………………………………………………………...……... ………………………………………………………………………………………………….. [2] [Total: 7]

4 ASRJC BIOLOGY DEPT 9744//2024/J2PRELIM//P2 2 The walls of alveoli in the lungs contain some specialised epithelial cells called type II epithelial cells. These cells secrete surfactant. Surfactant helps to prevent the alveoli collapsing during breathing. Surfactant is composed of phospholipid, cholesterol and protein. The components of surfactant are synthesised in the rough endoplasmic reticulum and smooth endoplasmic reticulum and then passed to the Golgi body. (a) Ribosomes are found on the surface of rough endoplasmic reticulum. Describe the structure of a ribosome. …………………………………………………………………………………………...…... ……………………………………………………………………………………………….. …………………………………………………………………………………………...…... ……………………………………………………………………………………………….. …………………………………………………………………………………………...…... …………………………………………………………………………………………...…... [3] (b) Identify the component(s) of surfactant that is (are) synthesised in the smooth endoplasmic reticulum. ……………………………………………………………………………………………….. [1]

5 ASRJC BIOLOGY DEPT 9744//2024/J2PRELIM/P2 [Turn over (c) Fig. 2.1 shows part of a type II epithelial cell. Fig. 2.1 Both the Golgi body and the smooth endoplasmic reticulum are part of the internal network of membranes in cells. Describe structural features shown in Fig. 2.1 that identify G as the Golgi body and not the smooth endoplasmic reticulum. …………………………………………………………………………………………...…... ……………………………………………………………………………………………….. …………………………………………………………………………………………...…... ……………………………………………………………………………………………….. …………………………………………………………………………………………...…... …………………………………………………………………………………………...…... [3]

6 ASRJC BIOLOGY DEPT 9744//2024/J2PRELIM//P2 (d) The surfactant that is produced is stored in secretory organelles called lamellar bodies. Each lamellar body is surrounded by a single membrane. The surfactant in the lamellar bodies is released onto the surface of the alveolar epithelium by exocytosis. Scientists studying the production and secretion of lung surfactant have discovered that a reduction in cholesterol in the cell surface membrane of type II epithelial cells reduces the secretion of surfactant. Explain why secretion of surfactant is affected by a reduction in cholesterol in the cell surface membranes of type II epithelial cells. …………………………………………………………………………………………...…... ……………………………………………………………………………………………….. …………………………………………………………………………………………...…... ……………………………………………………………………………………………….. …………………………………………………………………………………………...…... …………………………………………………………………………………………...…... [3] [Total: 10]

7 ASRJC BIOLOGY DEPT 9744//2024/J2PRELIM/P2 [Turn over 3 Keratin is the structural protein in feathers of birds. Keratin polypeptides are composed of a high proportion of cysteine amino acids. Keratin polypeptides form fibres. The two main types of keratin in feathers are α -keratin, which consists of many α-helices, and β-keratin, which consists of many β-pleated sheets. (a) Keratinases are proteases that can hydrolyse keratin. Many proteases are able to hydrolyse more than one type of protein. Explain why it is possible for a protease to act on different types of protein. …………………………………………………………………………………………...…...... ………………………………………………………………………………………………….. …………………………………………………………………………………………...…...... …………………………………………………………………………………………...…...... [2] (b) Feathers are not easily hydrolysed because keratin is a very stable protein. Suggest features of keratin structure that contribute to its stability. …………………………………………………………………………………………...…...... ………………………………………………………………………………………………….. …………………………………………………………………………………………...…...... …………………………………………………………………………………………...…...... [2]

8 ASRJC BIOLOGY DEPT 9744//2024/J