2024 NYJC Prelim Biology P2 (Q)

9744 / H2 Biology / 02 NANYANG JUNIOR COLLEGE JC 2 PRELIMINARY EXAMINATION Higher 2 CANDIDATE NAME CLASS BIOLOGY 9744/02 Paper 2 Structured Questions 10 September 2024 Candidates answer on the Question Paper. No Additional Materials are required. 2 hours READ THESE INSTRUCTIONS FIRST Write your name and CT on all the work you hand in. Write in dark blue or black pen. You may use an HB pencil for any diagrams or graphs. Do no use staples, paper clips, highlighters, 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 your working or if you do no use appropriate units. At the end of the examination, fasten all your work securely together. The number of marks is given in brackets [ ] at the end of each question or part question. For Examiner’s Use 1 2 3 4 5 6 7 8 9 10 11 Total This document consists of 30 printed pages and 0 blank pages. [Turn over

9744 / H2 Biology / 02 2 Answer all the questions in this section. 1 Candida albicans is a yeast-like fungus that lives in human lungs. It is the causati ve agent of one of the opportunistic infections that may develop during AIDS. C. albicans is eukaryotic. Fig. 1.1 shows its structure. Fig. 1.1 (a)(i) Name H to L. [2] (ii) State two ways in which the structure of a prokaryotic cell differs from that shown in Fig. 1.1. [2]

9744 / H2 Biology / 02 3 C. albicans uses a transport protein, TMP1, to absorb sugar molecules from the inside of the mouth. TMP1 is encoded by a gene within the nucleus and is produced when sugars are present in the surroundings. (b) Explain how the structures within the cell shown in Fig. 1.1, are involved with the production of functioning TMP1. [4] [Total: 8]

9744 / H2 Biology / 02 4 2 Table 2.1 contains statements about four molecules. (a) Complete the table by indicating with a tick ( ✓ ) or a cross ( ✘ ) whether the statements apply to haemoglobin, DNA, phospholipids or antibodies. You should put a tick or a cross in each box of the table. Table 2.1 statement haemoglobin DNA phospholipids antibodies contains phosphate able to replicate hydrogen bonds stabilise the molecule Contains nitrogen [4] (b) Haemoglobin is a globular protein that shows quaternary structure. It is composed of two types of polypeptide, known as α and β globin. (i) Explain how a globular protein differs from a fibrous protein, such as collagen. [2]

9744 / H2 Biology / 02 5 Fig. 2.1 shows part of the base sequence of the mRNA that codes for t he first ten amino acids of β globin. Table 2.2 shows some of the codons and the amino acids for which they code for. Fig. 2.1 Table 2.2 (ii) Use the information in Table 2.2 to complete the sequence of amino acids at the beginning of β globin using the first three letters of each amino acid. Some of them have been done for you. val his glu ala [2] (iii) β globin has a tertiary structure that consists of eight helices arranged to give a precise three-dimensional shape. Describe how the precise three-dimensional shape of a polypeptide is maintained. [3] [Total: 11]

9744 / H2 Biology / 02 6 3 Pepsin is an enzyme that hydrolyses proteins (protease). Some students used pepsin from the stomach of a mammal. The activity of the pepsin was investigated by placing a small quantity of the enzyme with a known concentration of the protein albumen. Fig. 3.1 shows the progress of the enzyme-catalysed reaction that was carried out at 20 °C. Fig. 3.1 (a) Calculate the initial rate of the reaction. initial rate of reaction = ......................................................... [2]

9744 / H2 Biology / 02 7 (b) The procedure was repeated to find the effects on the activity of the pepsin using a N-acetyl-statine, a competitive inhibitor at the same temperature, 20 °C. (i) Predict the results that will be obtained using the competitive inhibitor. [2] (ii) Explain how N-acetyl-statine inhibits the enzyme pepsin. [3] (c) Enzyme chymotrypsin is another protease synthesized by mammals. However chymotrypsin and pepsin are structurally different with different amino acid sequences. Explain how two enzymes with different amino acid sequences can catalyse the same reaction. [2] [Total: 9]

9744 / H2 Biology / 02 8 4 Telomere length has been associated with cell division and cell cycle arrest. Fig 4.1 shows the telomere length over time in various cell types. If telomeres are shortened t o a ‘critical length’, the cell will undergo permanent growth arrest or apoptosis. Fig. 4.1 (a) (i) With reference to Fig. 4.1, describe the difference in telomere length between normal cells and germ cells (cells that give rise to gametes) over time. [1] (ii) Telomerase results in the extension of the telomere length. Explain the signi ficance of telomerase in germ cells. [3]

9744 / H2 Biology / 02 9 (iii) Describe how telomerase extends telomere length. [4]

9744 / H2 Biology / 02 10 Transcriptional regulation of human telomerase (hTERT) gene is the major mechanism in regulating telomerase amount in human cells. The hTERT gene promoter is found t o be inactive in normal cells but is activated in germline cells and stem cells. The luciferase gene ( LUC) is placed under the control of hTERT gene promoter of varying lengths as shown in Fig. 4.2. Luciferase produces a fluorescent green protein when luciferin is added. The intensity of the florescence was quantified and the results are shown below. Fig. 4.2 (b) With reference to Fig. 4.2, explain the decrease in intensity of fluorescence when the region between -97 to -37 in the promoter is deleted. [2]