2025 DHS H2 Prelim Paper 2 (with answers)

© DHS 2025 9744/02 [Turn over Name: Centre/Index Number: Class: DUNMAN HIGH SCHOOL Preliminary Examination Year 6 H2 BIOLOGY 9744/02 Paper 2 Structured Questions (PART 1 of 2) 17 September 2025 2 hours Candidates answer on the Question Paper. No Additional Materials are required. READ THESE INSTRUCTIONS FIRST: Write your name, centre number, index number and class 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. This exam consists of two parts: Part 1 and Part 2. You must complete both Part 1 and Part 2. This is Part 1. Answer all questions in the spaces provided on the Question Paper. 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. For Examiner’s Use 1 11 2 9 3 11 4 11 5 8 This document consists of 32 printed pages and 4 blank pages.

2 © DHS 2025 9744/02 Answer all questions. 1 Fig. 1.1 is a transmission electron micrograph of a cell from the stem of sago pondweed, Stuckenia pectinata. Fig. 1.1 (a) (i) State the evidence from Fig. 1.1 that shows that the cell is from the stem of S. pectinata and not from the mesophyll of a leaf. [1] (ii) Complete each row in Table 1.1 to identify a cell structure shown in Fig. 1.1 that carries out the function listed. Table 1.1 function name of cell structure letter on Fig. 1.1 gas exchange production of subunits of ribosomes active transport of ions aerobic respiration [4]

3 © DHS 2025 9744/02 [Turn over (b) Plant vacuoles develop when vesicles fuse together. The vacuoles increase in size as more vesicles fuse. Fig. 1.2 shows the movement of vesicles within a plant cell during the development of a vacuole. Fig. 1.2 (i) Name the process that is occurring at X. [1] (ii) Some of the vesicles formed by the Golgi body fuse with the vacuole. These vesicles contain both proteins that have been folded correctly and incorrectly. Explain how proteins that have not been folded correctly are broken down in the vacuole. [3]

4 © DHS 2025 9744/02 (c) Small vacuoles in S. pectinata may have roles similar to lysosomes in animal cells. Describe the role of lysosomes in animal cells in defence against pathogens. [2] Total: [11]

5 © DHS 2025 9744/02 [Turn over Question 2 starts on page 6.

6 © DHS 2025 9744/02 2 Glycogen and cellulose are polymers. Fig. 2.1 shows small, representative regions of a glycogen molecule and a cellulose molecule. Fig. 2.1 (a) Describe three ways, visible in Fig. 2.1 , in which the molecule of glycogen differs from the molecule of cellulose. [3]

7 © DHS 2025 9744/02 [Turn over (b) Glycogen is found in the form of granules in mammalian liver and muscle cells. Fig. 2.2 is a diagram of part of a molecule of glycogen isolated from a glycogen granule. Fig. 2.2 Explain how the structure of glycogen is related to its function in cells. [3] (c) Explain how the arrangement of cellulose molecules in plant cell walls is related to their function. [3] Total: [9]

8 © DHS 2025 9744/02 3 Phosphate ions have a number of uses in organisms. These include: • involvement in cell signalling responses • involvement in energy transfer processes • component of phospholipids • component of nucleotides. Phosphatase enzymes remove phosphate groups from organic compounds, while kinase enzymes add phosphate groups. (a) Read the following passage: Some hormones circulating in the blood are able to trigger transcription within a cell, even though they are unable to enter the cell. Phosphatases and kinases then take part in cell activities that eventually result in genes switching on and transcription beginning. (i) Suggest why the hormones, referred to in the passage, are unable to enter the cell. [2] (ii) Use the information in the passage to outline the process of cell signalling. [3]

9 © DHS 2025 9744/02 [Turn over (b) The activity of a phosphatase enzyme was measured at different values of pH by using nine different buffer solutions. The temperature was kept constant at 30 °C. The results are shown in Fig. 3.1. Fig. 3.1 (i) With reference to Fig. 3.1, describe the effect of pH on the activity of phosphatase. [3] (ii) Explain why the activity of phosphatase at pH 1 is very low. [3] Total: [11]

10 © DHS 2025 9744/02 4 Two enzymes, DNA polymerase and DNA ligase, are involved in the replication of DNA. Fig. 4.1 shows the replication of part of human chromosome 11 by DNA polymerase. The arrows show the direction of synthesis of the new polynucleotides by DNA polymerase. Fig. 4.1 (a) (i) Compare DNA polymerase and DNA ligase in the replication of DNA. [5] (ii) State the name of the stage of interphase in the cell cycle when DNA replication occurs. [1]