DHS 2023 Y5 H2 Promo Paper 2

© DHS 2023 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 26 September 2023 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 9 2 11 3 7 4 8 Section B 1 15 2 15 Total 80 This document consists of 16 printed pages and 2 blank pages.

2 © DHS 2023 9744/02 Section A: Structured Questions Answer all questions. Question 1 Fig 1 is an electron micrograph of part of a eukaryotic cell. Fig 1 (a) Both the Golgi body and the rough endoplasmic reticulum are part of the network of membranes inside cells. Outline the structural features shown in Fig 1 that identify G as the Golgi body and not the rough endoplasmic reticulum. [2] (b) Calculate the actual diameter, X–Y, of the mitochondrion labelled in Fig 1. Write down the formula that you will use to make your calculation. Give your answer to the nearest whole nanometre (nm). formula Actual diameter = nm [2]

3 © DHS 2023 9744/02 [Turn over (c) Many of the cell structures in Fig 1 are surrounded by membranes. Membranes are approximately 6 nm to 7 nm wide. (i) Using your knowledge on fluid mosaic model , describe the structure of membranes. There is space below for a diagram. [3] (ii) The inner membrane of the mitochondrial envelope is much less permeable than the outer membrane. Suggest two ways in which the structure of the inner membrane of the mitochondrion may differ from that of the outer membrane to produce a less permeable inner membrane. [2] Total: [9]

4 © DHS 2023 9744/02 Question 2 Fig 2.1 shows a polypeptide molecule during protein synthesis. A molecule of glycine is shown just before it is added to the polypeptide. The product formed is incomplete. Fig 2.1 (a) (i) Complete Fig 2.1 to show how the products are formed. [3] (ii) Name the enzyme that catalyses the above reaction in cells. [1]

5 © DHS 2023 9744/02 [Turn over Enzymes can be used to speed up the rate of reaction. When developing an enzyme - catalysed reaction for use in industry, the progress of the reaction is studied. (b) Outline how , in the production of lactose -free milk, the progress of a lactase- catalysed reaction can be investigated experimentally. [3]

6 © DHS 2023 9744/02 The feet of elephants are protected by structures under the skin known as cushions, as shown in Fig 2.2. Fig 2.2 The cushions are made up of a large number of cells surrounded by connective tissues containing many fibres of collagen. The fibres help to maintain the structure of the cushions. The collagen fibres are made of collagen molecules. Fig 2.3 Osteogenesis imperfecta (OI), commonly known as "brittle bone disease", is a disorder characterized by bone fragility and abnormalities of connective tissue s. Vast majority of affected individuals have mutations in the genes coding the polypeptide chains of collagen, which result in change of amino acid residues. (c) With reference to Fig 2.3, describe the effect of such change in amino acid to the structure of collagen fibre. [2]

7 © DHS 2023 9744/02 [Turn over Collagen is a water -insoluble fibrous protein that can be prone to swelling. Collagen swelling occurs when water fills up the gaps between collagen molecules. Fig 2.4 shows the effects of pH on the swelling ratio of collagen. Swelling ratio is defined as the percentage increase in the weight of collagen due to water absorption. Fig 2.4 (d) With reference to Fig 2.4, describe and explain the effects of pH on collagen when the time is 8h. [2] Total: [11]

8 © DHS 2023 9744/02 Question 3 A salamander species, Notophthalmus viridescens (newt) has an ability to regenerate its limbs after amputation. The muscle cells of newt can undergo reprogramming and dedifferentiation to return to a less differentiated state. These dedifferentiated cells can proliferate to form a blastema. Cells in the blastema can then differentiate into different cell types to give rise to a newly formed limb. Fig 3.1 shows a flow chart of the dedifferentiation and differentiation processes after the amputation. Fig 3.1 (a) Name the nuclear division involved in the formation of blastema shown in Fig 3.1. [1] (b) The cells in the blastema are genetically identical and have low or no expression of the myosin heavy chain (MYC) protein. However, the muscle cells have a high level of expression of the MYC protein. Describe how the expression of the MYC gene in the muscle cells may be controlled at the translational level. [2]

9 © DHS 2023 9744/02 [Turn over Scientists compared the species richness (number of unique species), the average body size in centimetres (cm) and the average genome size in picograms (pg) of different families of organisms. The results are shown in Fig 3.2. Fig 3.2 (c) (i) Comment on the relationship between the average body size and average genome size shown in Fig 3.2. [2] (ii) Suggest possible reasons for the difference in the average genome size between salamanders and the Enterobacteriaceae bacterial species. [2] Total: [7]

10 © DHS 2023 9744/02 Question 4 A group of researchers created a DNA construct, fusing elements of the Trp operon to the Lac operon. The DNA construct was then transformed into E. coli that lack the Lac and Trp operon. Fig 4 illustrates the fusion between the two operons. Fig 4 (a) Describe how the DNA construct containing the Trp-Lac fusion operon can be taken into the E. coli cell by transformation. [2]