DHS 2022 Y5 H2 Promo Paper 2 (QP)

© DHS 2022 9744/02 [Turn over Name: Index Number: Class: DUNMAN HIGH SCHOOL Promotional Examination Year 5 H2 BIOLOGY 9744/02 Paper 2 Section A (Structured Questions) 27 September 2022 Paper 2 Section B (Long Structured and Free-Response Questions) 1 hour 30 minutes READ THESE INSTRUCTIONS FIRST: Write your class, index number and name 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. Sections A and B 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 Paper 1 MCQ 15 Paper 2 Section A 1 6 2 10 3 9 4 10 Section B 1 15 2 15 Total 80 This document consists of 15 printed pages and 3 blank pages.

2 © DHS 2022 9744/02 Section A: Structured Questions Answer all questions. Question 1 Fig 1 shows a part of the collagen synthesis pathway at the rough endoplasmic reticulum. Fig 1 With reference to Fig 1, (a) (i) name the most common amino acid in procollagen chain, [1] (ii) name the bond that stabilises the procollagen trimer, [1] (b) describe how collagen fibrils are synthesized outside the cell from procollagen trimers. [4] Total: [6]

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4 © DHS 2022 9744/02 Question 2 Polygalacturonase (PG) plays an important role in fruit softening by making the pectin of the cell wall more soluble. In order to slow down the ripening of tomatoes, antisense RNA technology was used where a second copy of the gene was inserted into the tomato genome in the antisense direction (transformed fruit). PG antisense RNA has a sequence which is complementary to PG mRNA. When the gene coding for antisense RNA is expressed, it interferes with the production of the PG, delaying the ripening process. mRNA extracted from ripe and unripe untransformed and transformed fruits were hybridised to radioactively labelled pr obes specific to the PG sense strand. Fig 2 shows the results expressed as the percentage of PG mRNA in ripe untransformed fruit. Fig 2 100 90 80 70 60 50 40 30 20 10 0

5 © DHS 2022 9744/02 [Turn over (a) Contrast the process of the synthesis of PG mRNA and the synthesis of PG in a cell. [4] (b) Explain how the antisense RNA technology affects ripe transformed fruits. [4]

6 © DHS 2022 9744/02 (c) PGs can also be produced by pathogens to degrade plant cell walls and invade tissues. In plant defense, polygalacturonase-inhibiting proteins (PGIPs) are produced in cell walls to inhibit the activity of such PGs. Upon an infection, it was observed that • the same plant exhibits different degrees of susceptibility to different pathogenic PGs. • different plants also exhibit different degrees of susceptibility to the same pathogenic PGs. The different cell wall compositions in different plants might explain the different degrees of susceptibility observed. Suggest other reasons for the differing degrees of susceptibility observed. [2] Total: [10]

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8 © DHS 2022 9744/02 Question 3 Fig 3.1 shows the function of permease in the cell surface membrane of E. coli. Created in Biorender.com Fig 3.1 (a) With reference to Fig 3.1, describe the function of permease. [2] (b) Permease is encoded by the lacY gene of lac operon. Explain how an increase in lactose concentration changes the amount of permease in the cell surface membrane of E. coli. [5]

9 © DHS 2022 9744/02 [Turn over (c) Folding of polypeptides in a cell typically requires the assistance of molecular chaperones, a class of protein complexes. Fig 3.2 shows the chaperone complex that assist s the folding of polypeptide into permease. Edited from Matthew J Shurtleff (2018). Fig 3.2 Suggest why this chaperone is embedded within the membrane. [2] Total: [9]

10 © DHS 2022 9744/02 Question 4 The mitotic cell cycle in the somatic cells of a diploid organism can be followed by measuring the number of chromosomes and the amount of DNA material per cell over a period of time. Fig 4 shows the results of the analysis, beginning with the start of mitosis. Fig 4 (a) (i) On Fig 4, indicate with an arrow () where anaphase begins. [1] (ii) Explain your answer in (a)(i). [3]