YIJC 2023 H2 9744 P2 QP

1 @YIJC 9744/02/PE/2023 [Turn over YISHUN INNOVA JUNIOR COLLEGE JC2 PRELIMINARY EXAM Higher 2 NAME INDEX NO CG BIOLOGY Paper 2 Structured Questions Candidates answer on the Question Paper. No Additional Materials are required. 9744/02 30 Aug 2023 2 hours READ THESE INSTRUCTIONS FIRST Write your name, index no. and CG on this cover page. Write in dark blue or black pen on both sides of the paper. You may use a soft pencil for any diagrams, graphs or rough working. Do not use staples, paper clips, highlighters, glue or correction fluid. 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 This document consists of 23 printed pages and 1 blank page. For Examiner’s Use Section A 1 10 2 10 3 8 4 10 5 10 6 12 7 10 8 10 9 10 10 5 11 5 Total 100

2 @YIJC 9744/02/PE/2023 Answer all questions. 1 Fig. 1.1 shows an electron micrograph of a chloroplast. Fig. 1.1 (a) (i) On Fig. 1.1, use the letter X and a label line to identify where the light - independent stage of photosynthesis occurs. [1] (ii) Describe two ways in which the structure of the chloroplast is adapted for its function. [2] (iii) Both the c hloroplast and the mitochondrion have double membranes. State two other structural similarities between the chloroplast and the mitochondrion. [2]

3 @YIJC 9744/02/PE/2023 [Turn over (b) Fig. 1.2 shows the relationship between CO 2 assimilation rate and increasing light intensity on a plant, when carbon dioxide concentration is not a limiting factor. Fig. 1.2 (i) Explain why the CO2 assimilation rate plateaus at high light intensity. [3] (ii) Describe what is occurring at point A. [2] [Total: 10]

4 @YIJC 9744/02/PE/2023 2 An investigation was carried out to find the optimum pH and the optimum temperature of an amylase obtained from the bacterium Anoxybacillus thermarum. Fig. 2.1 shows the results of the investigation. Fig. 2.1 (a) With reference to Fig. 2.1, c ompare the effect of temperature on the activity of the amylase and the effect of pH on the activity of the amylase. [3] (b) Explain the percentage activity of amylase at X. [3] X

5 @YIJC 9744/02/PE/2023 [Turn over Table 2.1 shows the optimum pH and optimum temperature for amylase from different species of bacteria. Table 2.1 (c) (i) Using the data in Fig. 2.1 and Table 2.1, identify the bacterial species that has amylase most similar to amylase from Anoxybacillus thermarum. [1] (ii) Suggest why the amylase molecules of some species of bacteria are able to work at higher temperatures than others. [3] [Total: 10]

6 @YIJC 9744/02/PE/2023 3 (a) Stem cells from the human bone marrow that are involved in blood cell formation are described as multipotent, rather than totipotent. Compare multipotent and totipotent stem cells. [2] (b) Some fully differentiated cells can be stimulated to change back into stem cells in tissue culture. Such cells are called induced pluripotent stem cells (iPS cells). In in vitro experiments with human cells , it was discovered that the introduction of five genes would cause fully differentiated skin fibroblast cells to change to iPS cells. There is evidence to suggest that the introduction of the five genes caused an increase in the production of telomerase reverse transcriptase (TERT) in the fully differentiated cells. (i) Explain how TERT may help to change the fully differentiated cells back into stem cells. [3] (ii) Explain why it may be advantageous to use iPS cells for treating diseases in humans, instead of performing organ or tissue transplant. [2] (c) Suggest why the use of stem cells in treatment gives a greater risk of cancer in the future. [1] [Total: 8]

7 @YIJC 9744/02/PE/2023 [Turn over 4 Fig. 4.1 shows the structure of TLA-1 virus, a newly discovered virus which causes coral disease. Fig. 4.1 (a) Describe two differences between the structures of TLA -1 virus and the Human Immunodeficiency Virus (HIV). [2]

8 @YIJC 9744/02/PE/2023 Fig. 4.2 shows the number of T helper cells in the blood and the number of HIV viruses in the body over the course of an untreated HIV infection. Fig. 4.2 (b) (i) Describe the changes shown in Fig. 4.2. [2] (ii) Suggest how the changes in the number of T helper cells from year 1 to year 10 would affect the health of the untreated HIV patient. [2] (iii) Explain why HIV is considered a retrovirus. [2]

9 @YIJC 9744/02/PE/2023 [Turn over (iv) Explain why viruses are considered obligate parasites. [2] [Total: 10]

10 @YIJC 9744/02/PE/2023 5 Fig 5.1 shows the electron micrographs of two stages of meiosis, J and K. stage J stage K Fig. 5.1 (a) Name the stages of meiosis labelled J and K in Fig. 5.1 and describe the behaviour of chromosomes in each of these stages. stage J behaviour of chromosomes in J stage K behaviour of chromosomes in K [4]