2024 EJC Prelim Biology P2 (Q)

©EJC 2024 9744/02/J2H2PRELIM/2024 [Turn over EUNOIA JUNIOR COLLEGE JC2 Preliminary Examinations 2024 General Certificate of Education Advanced Level Higher 2 CANDIDATE NAME CIVICS GROUP 2 3 - REGISTRATION NUMBER H2 Biology Paper 2 Structured Questions 9744/02 11 September 2024 2 hours READ THESE INSTRUCTIONS FIRST Write your name, civics group and registration number on all the work you hand in. Candidates are to answer: All questions on the Question Paper. Write your answers in dark blue or black pen. You may use an HB pencil for any diagrams or graphs. Do not use paper clips, highlighters, glue, or correction fluid/tape. The use of an approved scientific calculator is expected, where appropriate. The number of marks is given in brackets [ ] at the end of each question or part question. This document consists of 29 printed pages and 3 blank pages. For Examiner’s Use 1 2 3 4 5 6 7 8 9 10 11 Total

2 ©EJC 2024 9744/02/J2H2PRELIM/2024 BLANK PAGE

3 ©EJC 2024 9744/02/J2H2PRELIM/2024 [Turn over Answer all questions. 1 The unicellular fungus Kluyveromyces lactis is found in dairy products. It is a safe microorganism to culture for the extraction of the enzyme lactase. Lactase catalyses the breakdown of lactose, a sugar found in milk. The reaction catalysed by lactase is summarised in Fig. 1.1. Fig. 1.1 (a) Describe the reaction that is catalysed by lactase. Use Fig. 1.1 to help you. In you r answer, identify Y and product Z. ………………………………………………………………………………………………………… ………………………………………………………………………………………………………… ………………………………………………………………………………………………………… ………………………………………………………………………………………………………… ………………………………………………………………………………………………………… ……………………………...……………………………………………………………………... [3] (b) On a commercial scale, immobilised lactase can be used to produce lactose-free milk. One of the products of the reaction shown in Fig. 1.1 acts as an inhibitor of lactase. This is an example of product inhibition. (i) Suggest why product inhibition is advantageous in K. lactis when lactase is acting as an intracellular enzyme but can be a disadvantage when extracted lactase is used free in solution to produce lactose-free milk. ………………………………………………………………………………………………… ………………………………………………………………………………………………… …………………………………………………………………………………………………

4 ©EJC 2024 9744/02/J2H2PRELIM/2024 ……………………...……………………………………………………………………… [2] (ii) Suggest how using immobilised lactase for the production of lactose-free mi lk helps to reduce the problem of product inhibition. ………………………………………………………………………………………………… ………………………………..…………………………………………………………… [1] (c) When developing an enzyme-catalysed reaction for use in industry, the progress o f the reaction is studied to determine the optimal conditions for product formation. Explain how substrate concentration can affect the rate of an enzyme-catalysed reaction. ………………………………………………………………………………………………………… ………………………………………………………………………………………………………… ………………………………………………………………………………………………………… ………………………………………………………………………………………………………… ………………………………………………………………………………………………………… ………………………………………………………………………………………………………… ………………………………………………………………………………………………………… ...…………………………………………………………………………………………………... [4] [Total: 10]

5 ©EJC 2024 9744/02/J2H2PRELIM/2024 [Turn over 2 Lysosomes are cell structures that contain acid hydrolases which are enzymes that work best in acidic environments. Fig. 2.1 shows some processes that occur in neutrophils. Fig. 2.1 (a) Name the cell structures labelled A and E. A ……………………………………………………. E ……………………………………………………. [1] (b) State the function of F. ……………………………………………………………………………………………………….... …………………………………………………………………………………………………….. [1]

6 ©EJC 2024 9744/02/J2H2PRELIM/2024 (c) Describe the role of cell surface membrane during process C. ……………………………………………………………………………………………………….... ………………………………………………………………………………………………………… ……………………………………………………………………………………………………….... ………………………………………………………………………………………………………… ……………………………………………………………………………………………………….... …………………………………………………………………………………………………….. [3] (d) With reference to the processes occurring at B and at D in Fig. 2.1, outline the roles of acid hydrolases in lysosomes. ……………………………………………………………………………………………………….... ………………………………………………………………………………………………………… ……………………………………………………………………………………………………….... ………………………………………………………………………………………………………… ……………………………………………………………………………………………………….... ………………………………………………………………………………………………………… ……………………………………………………………………………………………………….... …………………………………………………………………………………………………….. [4] (e) Carrier proteins in the membranes of lysosomes maintain a lower pH than the surrounding cytoplasm by moving hydrogen ions. Suggest how the carrier proteins maintain the lower pH within the lysosomes. ……………………………………………………………………………………………………….... …………………………………………………………………………………………………….. [1] [Total: 10]

7 ©EJC 2024 9744/02/J2H2PRELIM/2024 [Turn over 3 The early development of an animal involves divisions of the zygote and daughter cells by mitosis to form an embryo consisting of genetically identical cells. Fig. 3.1 shows several cells at different stages of the cell cycle in an embryo of w hitefish, Coregonus artedi. Fig. 3.1 (a) (i) Name the stage of mitosis in cell A and in cell C, shown in Fig. 3.1. A ………………………………………………………… [1] C ………………………………………………………… [1] (ii) Describe the role of microtubules in cell B. …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... ……………………………………………………………………………………………….. [2]

8 ©EJC 2024 9744/02/J2H2PRELIM/2024 (b) Uncontrolled mitosis can cause cancer in humans. Paclitaxel is a drug used in the treatment of some forms of cancer. Researchers investigated the effect of Paclitaxel on the mitotic cell cycle of cancer cells.  The cancer cells were grown for two days and then divided into groups.  Each group was treated with a different concentration of Paclitaxel. After 28 hours (one cell cycle):  the percentage of cells in stages of mitosis was calculated  the ratio of the number of cells in anaphase to the number of cells in metaphase was determined. The results of the investigation are shown in Fig. 3.2. Fig. 3.2

9 ©EJC 2024 9744/02/J2H2PRELIM/2024 [Turn over With reference to Fig. 3.2, describe the results and suggest an explanation for the effect of Paclitaxel on the mitotic cell cycle. ……………………………………………………………………………………………………….... ………………………………………………………………………………………………………… ……………………………………………………………………………………………………….... ………………………………………………………………………………………………………… ……………………………………………………………………………………………………….... ………………………………………………………………………………………………………… ……………………………………………………………………………………………………….... …………………………………………………………………………………………………….. [4] (c) Fig 3.3 depicts a model of cancer development from a single abnormal cell. Fig 3.3 Explain what may have led to the development of this abnormal cell from a normal cell before it divides rapidly. ……………………………………………………………………………………………………….... ………………………………………………………………………………………………………… ……………………………………………………………………………………………………….... …………………………………………………………………………………………………….. [2] [Total: 10]

10 ©EJC 2024 9744/02/J2H2PRELIM/2024 4 In typical cells, nucleic acids are synthesised from eight different nucleotides. Fig. 4.1 represents the three different components of a nucleotide. Fig. 4.1 (a) Describe how differences in these components result in the eight different nucleot ides from which nucleic acids are synthesised. ……………………………………………………………………………………………………….... ………………………………………………………………………………………………………… ……………………………………………………………………………………………………….... …………………………………………………………………………………………………….. [2]