TJC 2023 H2 BIO P2 QP

1 [TURN OVER READ THESE INSTRUCTIONS FIRST Write your Center number, index number and name in the spaces 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. DO NOT WRITE IN ANY BARCODES. 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 any working or if you do not use appropriate units. TEMASEK JUNIOR COLLEGE 2023 JC2 PRELIMINARY EXAMINATION Higher 2 CANDIDATE NAME CENTRE NUMBER S INDEX NUMBER BIOLOGY 9744/02 Paper 2 Structured Questions (Part I) 25 AUGUST 2023 2 hours Candidates answer on the Question Paper. No Additional Materials are required. The number of marks is given in brackets [ ] at the end of each question or part question. For Examiner’s Use 1 / 12 2 / 11 3 / 11 4 / 10 5 / 8 Answer all questions. This document consists of 16 printed pages.

2 Answer all questions. 1 Fig. 1.1 shows an electron micrograph of a plant cell. Fig. 1.1 (a) Identify the organelles labelled A, B, and C in Fig. 1.1. A: ………………………………………………………………….. B: ………………………………………………………………….. C: ………………………………………………………………….. [3] (b) Use a line to label the cell wall, D. [1] (c) The magnification of the photomicrograph is 560x. Calculate the actual length of organelle C in μm, along the line P-Q. Show your working. actual length of organelle C: ………………………………. μm [2]

3 [TURN OVER (d) Compare the structural features of organelle A and organelle B. …………………………………………………………………………………………………………………. …………………………………………………………………………………………………………………. …………………………………………………………………………………………………………………. …………………………………………………………………………………………………………………. ……………………………………………………………………………………………………………… [2]

4 (e) A factor that can limit the rate of photosynthesis is the rate of regeneration of RuBP. Sedoheptulose-1,7-bisphosphatase (SBPase) is an enzyme in the Calvin cycle that controls the rate of regeneration of RuBP. SBPase is coded for by the gene SBPase , which is present in most plants. In an experiment, 2 wheat plants were studied. • one was genetically modified to make more SBPase by introducing the SBPase gene from another grass species. • one was not modified (wild type). Fig. 1.2 shows the mean mass of plant for the wild type plants and genetically modified plants. Fig. 1.2 Suggest and explain why genetically modified plants have a different mean mass than wild type plants. ……………………………………………………………………………………………………………. ….………………………………………………………………………………………………………… …….……………………………………………………………………………………………………… …….……………………………………………………………………………………………………… ……….…..………….…..………………………………………………………………………….……. ……………………………………………………………………………………………………………. ….………………………………………………………………………………………………………… …….……………………………………………………………………………………………………… …….…………………………………………………………………………………………………... [4] [Total: 12] mean mass of plant / g genetically modified wild type

5 [TURN OVER Question 2 starts on Page 6.

6 2 Fig. 2.1 shows an electron micrograph of a mitochondrion. The labelled arrows X and Y both represent a structural feature of this organelle. Fig. 2.1 The table below shows the protein composition of various areas in the mitochondrion in Fig. 2.1. Table 2.1 labels protein composition / % X 6 Y 21 region between X and Y 6 inside mitochondria 67 total 100

7 [TURN OVER (a) Using the information in Table 2.1 above, (i) state the name of the structures labelled X and Y; X ………………………………………………………………………………………………………... Y …………………………………………………………………………………………………….. [2] (ii) account for the abundance of protein inside the mitochondrion. ………………………………………………………………………………………………………… ….……………………………………………………………………………………………………… …….…………………………………………………………………………………………………… …….………………………………………………………………………………………………… [2] Newborns have a large amount of brown fat tissue, which contains abundant mitochondria. Brown fat cells express the protein, thermogenin, which is embedded in the inner mitochondrial membrane. Protons flow through the channel in thermogenin instead of ATP synthase. As a result, the proton gradient is less steep, and energy is released in the form of heat. This keeps the babies warm. The mitochondrial matrix has a pH of about 7.8. The intermembrane space of mitochondria in different cells exhibits different pH values, as shown in Table 2.2. Table 2.2 cells from which mitochondria are isolated pH in intermembrane space resting muscle 7.0 muscle during exercise 6.8 brown fat 7.4 (b) (i) Explain the difference in pH values in the intermembrane space and the matrix of the mitochondria in the resting muscle cells. ………………………………………………………………………………………………………… ….……………………………………………………………………………………………………… ………………………………………………………………………………………………………… ….……………………………………………………………………………………………………… …….…………………………………………………………………………………………………… …….…………………………………………………………………………………………………… …….………………………………………………………………………………………………… [3]

8 (ii) Explain how low oxygen concentration will result in the newborns suffering from a drop in body temperatures. ………………………………………………………………………………………………………… ………………………………………………………………………………………………………… ….……………………………………………………………………………………………………… …….…………………………………………………………………………………………………… …….………………………………………………………………………………………………… [2] (iii) The respiratory processes in the mitochondria require oxygen. Explain how oxygen is transported into the mitochondria. ………………………………………………………………………………………………………… ………………………………………………………………………………………………………… ….……………………………………………………………………………………………………… …….…………………………………………………………………………………………………… …….………………………………………………………………………………………………… [2] [Total: 11]

9 [TURN OVER 3 Glycogen phosphorylase is an enzyme involved in glycogenolysis. Fig 3.1 shows a model of the enzyme glycogen phosphorylase. Glycogen phosphorylase catalyses the hydrolysis of glycosidic bonds to break up glycogen into glucose subunits. The active site of glycogen phosphorylase is located in a slight depression on one side of the molecule. The three amino acids that form the active site are Serine, Histidine and Aspartic Acid. These three amino acids are some distance apart on the polypeptide chain but close together in the active site. Fig. 3.1 (a) Explain how the substrate may be attached to the enzyme. …………………….………………………………………………………………………………………… …………………….………………………………………………………………………………………… …………………….………………………………………………………………………………………… …………………….………………………………………………………………………………………… .……………….…..……………………………………………………………………………………… [2] (b) Explain what determines the precise position of the three amino acids in the active site of the enzyme. …………………….………………………………………………………………………………………… …………………….………………………………………………………………………………………… …………………….………………………………………………………………………………………… …………………….………………………………………………………………………………………… …………………….………………………………………………………………………………………… …………………….………………………………………………………………………………………… .……………….…..……………………………………………………………………………………… [3]

10 (c) On Fig. 3.2, draw the predicted changes in enzyme activity as pH changes. Fig. 3.2 [1]