2025 ASRJC H2Bio PE P2 QP

H2 ANDERSON SERANGOON JUNIOR COLLEGE HIGHER 2 2025 JC2 PRELIMINARY EXAMINATIONS CANDIDATE NAME CLASS 2 5 / INDEX NUMBER BIOLOGY 9744/02 Paper 2 Structured Questions Candidates answer on the Question Paper. No Additional Materials are required. 22 August 2025 Friday 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. The number of marks is given in brackets [ ] at the end of each question or part question. This document consists of 31 printed pages and 1 blank page. For Examiner’s Use 1 / 9 2 / 9 3 / 11 4 / 10 5 / 10 6 / 9 7 / 10 8 / 10 9 / 10 10 / 7 11 / 5 Total /100

2 ASRJC BIOLOGY DEPT 9744/2025/J2PRELIM/P2 Answer all the questions. 1 Stem cells are found throughout the human body. Lgr5 + stem cells are found in the lining of the small intestine. Fig. 1.1 shows stages in the development of one of the daughter cells produced by the mitotic division of an Lgr5+ stem cell. Fig. 1.1 (a) Explain why Lgr5+ stem cells are required in the lining of the small intestine. …………………………………………………………………………………………...……........... …………………………………………………………………………………………………........... …………………………………………………………………………………………...……........... …………………………………………………………………………………………………........... …………………………………………………………………………………………...……........... ………………………………………………………………………………………………….......[3]

3 ASRJC BIOLOGY DEPT 9744/2025/J2PRELIM/P2 [Turn over (b) Fig. 1.2 shows a goblet cell, one of the specialised cells that develops from Lgr5+ stem cells in the small intestine. Fig. 1.2 Identify the structures labelled A and B, as shown in Fig. 1.2. For each structure, state its function and one identifying feature that can be seen in Fig. 1.2. structure A …………………………………………………………………..………………............ function ………………………………..……………………………………………………………... ………………………………………………………………………………………………………… identifying feature ................................................................................................................... ………………………………………………………………………………………………………… structure B …………………………………………………………………..………………............ function ………………………………..……………………………………………………………... ………………………………………………………………………………………………………… identifying feature ................................................................................................................... ………………………………………………………………………………………………………[6] [Total: 9]

4 ASRJC BIOLOGY DEPT 9744/2025/J2PRELIM/P2 2 Neutrase® is an enzyme that is used to hydrolyse proteins in solution. When the enzyme is mixed with a 2% protein solution, the reaction mixture changes from white to colourless. A student carried out an experiment to find the effect of copper sulfate and potassium sulfate on the activity of Neutrase®. The student made four reaction mixtures in test-tubes A to D. Test-tubes A to C contained equal volumes of protein solution and 0.1cm 3 of solutions of copper sulfate or potassium sulfate. Test-tube D contained the same volume of protein solution and 0.1 cm3 of water. 0.5 cm 3 of a 1% Neutrase® solution was added to test -tube A and immediately placed into a colorimeter. The colorimeter was used to measure the intensity of light that is absorbed by the solution (absorbance) over 100 seconds. The procedure was repeated with the other reaction mixtures, B, C and D. The results are shown in Fig. 2.1. Fig. 2.1 (a) Suggest and explain why measuring the absorbance of the reaction mixture over 100 s is a suitable method for determining the activity of Neutrase®. …………………………………………………………………………………………...……........... …………………………………………………………………………………………………........... …………………………………………………………………………………………...……........... ………………………………………………………………………………………………….......[2]

5 ASRJC BIOLOGY DEPT 9744/2025/J2PRELIM/P2 [Turn over (b) With reference to Fig. 2.1, (i) describe the effects of copper sulfate solution and potassium sulfate solution on the activity of Neutrase®. …………………………………………………………………………………………...……... ………………………………………………………………………………………………….. …………………………………………………………………………………………...……... ………………………………………………………………………………………………….. …………………………………………………………………………………………...……... ………………………………………………………………………………………………….. …………………………………………………………………………………………...……... ………………………………………………………………………………………………..[4] (ii) suggest explanations for the effects described in (b)(i). …………………………………………………………………………………………...……... ………………………………………………………………………………………………….. …………………………………………………………………………………………...……... ………………………………………………………………………………………………….. …………………………………………………………………………………………...……... ………………………………………………………………………………………………..[3] [Total: 9]

6 ASRJC BIOLOGY DEPT 9744/2025/J2PRELIM/P2 3 Fig. 3.1 shows a pie chart which represents the different stages of the cell cycle of an animal cell. One complete cycle takes 12 hours at 22 oC. Fig. 3.1 (a) (i) Express as a whole number ratio the total time spent on cell growth to the time spent on production of chromatids at 22 oC. whole number ratio ………………………….. [1] (ii) Express the time spent on mitosis as a percentage of the total time required for one cycle at 22 oC. Give your answer to 3 significant figures. time spent on mitosis………………………………………% [1]

7 ASRJC BIOLOGY DEPT 9744/2025/J2PRELIM/P2 [Turn over (iii) The cell cycle is controlled by check points. Identify the checkpoint between stage P and stage Q and state its function. …………………………………………………………………………………………...…….. …………………………………………………………………………………………...…….. …………………………………………………………………………………………………. …………………………………………………………………………………………...…….. ……………………………………………………………………………………………….[2]

8 ASRJC BIOLOGY DEPT 9744/2025/J2PRELIM/P2 (b) Fig. 3.2 is a transmission electron micrograph of two human chromosomes at metaphase of mitosis, stage S of the cell cycle. Fig. 3.2 (i) Outline how DNA molecules are packed to form the chromosomes shown in Fig. 3.2. …………………………………………………………………………………………...……........... …………………………………………………………………………………………………........... …………………………………………………………………………………………...……........... …………………………………………………………………………………………………........... …………………………………………………………………………………………...……........... ……………………………………………………………