HCI H2 Bio 2024 Prelim P2 Qn

© Hwa Chong Institution 2024 9744 H2 Biology / JC2 Preliminary Examinations / Paper 2 HWA CHONG INSTITUTION JC2 Preliminary Examinations Higher 2 CANDIDATE NAME CT GROUP 23S7__ CENTRE NUMBER INDEX NUMBER BIOLOGY Paper 2 Structured Questions Candidates answer on the Question Paper. No Additional Materials are required. 9744/02 22 August 2024 2 hours INSTRUCTIONS TO CANDIDATES There are six question booklets (I - VI) to this paper. Write your name, CT group, Centre number and index number in the spaces provided at the top of this cover page and on the lines provided at the top of the cover pages of Booklets II, III, IV, V and VI. There are eleven questions. Answer all questions in the spaces provided on the Question Paper. INFORMATION FOR CANDIDATES 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. You are reminded of the need for good English and clear presentation in your answers. This document consists of 25 printed pages. For Examiners' Use 1 / 9 2 / 8 3 / 10 4 / 10 5 / 10 6 / 10 7 / 13 8 / 10 9 / 10 10 / 5 11 / 5 Total / 100

2 © Hwa Chong Institution 2024 9744 H2 Biology / JC2 Preliminary Examinations / Paper 2 QUESTION 1 Fig 1.1 shows the amoeba, a unicellular organism that inhabit s freshwater ponds. It exhibits characteristic motility. Fig. 1.1 (a) Describe one feature visible in Fig. 1.1 that identifies the amoeba as a eukaryotic organism. [1] The amoeba contains structures called contractile vacuoles. They expel excess water from the cell. A contractile vacuole first increases in size, then migrates to and fuses with the cell surface membrane. Proteins, synthesised using the endomembrane system, are embedded within the membrane of these contractile vacuoles where they pump ions into the lumen of the contractile vacuoles. (b)(i) Explain how the structure of the contractile vacuole membrane enables it to perform its function. [4]

3 © Hwa Chong Institution 2024 9744 H2 Biology / JC2 Preliminary Examinations / Paper 2 (c)(ii) Explain how organelles of the endomembrane system are involved in the synthesis of proteins embedded within the membranes of contractile vacuoles. [4] [Total: 9]

4 © Hwa Chong Institution 2024 9744 H2 Biology / JC2 Preliminary Examinations / Paper 2 QUESTION 2 Keratin is the structural protein in the feathers of birds. Keratin polypeptides are composed of a high proportion of cysteine amino acids, which have sulfur-containing R groups. Keratin polypeptides form filaments. The two main types of keratin in feathers are α -keratin, which consists of many α-helices, and β-keratin, consisting of many β-pleated sheets. (a) Keratin can be classified as α-keratin or β-keratin based on a study of protein structure. Suggest the level of protein structure used to classify a protein as α-keratin or β-keratin. [1] Feathers are not easily degraded (broken down) because keratin is a very stable protein. Fig. 2.1 shows the structure of β-keratin in feathers. Fig. 2.1 β-pleated sheet β-keratin polypeptide β-keratin dimer β-keratin fibril β-keratin fibre

5 © Hwa Chong Institution 2024 9744 H2 Biology / JC2 Preliminary Examinations / Paper 2 (b) With reference to Fig. 2.1, describe features of keratin structure that contribute to its stability. [4] (c) Keratinase is a type of protease that catalyses the hydrolysis of α-keratin and β-keratin. Many proteases are able to hydrolyse more than one type of protein. Explain why it is possible for a protease to act on different types of protein. [3] [Total: 8]

6 © Hwa Chong Institution 2024 9744 H2 Biology / JC2 Preliminary Examinations / Paper 2 QUESTION 3 Fig. 3.1 shows the flow of genetic information from DNA to RNA to polypeptide, according to the central dogma of molecular biology. Fig. 3.1 (a)(i) Name molecules A and B. A B [2] (ii) With reference to molecules A and B, discuss the role of hydrogen bonds in translation. [2] nucleus cytoplasm B A

7 © Hwa Chong Institution 2024 9744 H2 Biology / JC2 Preliminary Examinations / Paper 2 Transcription and DNA replication are processes involving polymerisation. (b) Describe the differences between transcription and DNA replication. [3] Abacavir is an analogue used in the treatment of some viral diseases. It enters a cell infected by a virus and is metabolised to the analogue carbovir triphosphate. Fig. 3.2 shows the molecular structure of abacavir and carbovir triphosphate. Fig. 3.2 (c) Carbovir triphosphate can be inserted into an elongating polynucleotide chain instead of a nucleotide. This interferes with the action of DNA polymerase during the synthesis of viral DNA. Explain how carbovir triphosphate may prevent the synthesis of viral DNA. [3] [Total: 10] abacavir carbovir triphosphate

8 © Hwa Chong Institution 2024 9744 H2 Biology / JC2 Preliminary Examinations / Paper 2 QUESTION 4 Fig. 4.1 shows the structure of a coronavirus, SARS-CoV, which caused the Severe Acute Respiratory Syndrome (SARS). Infection by SARS-CoV causes symptoms resembling influenza that can be deadly. Fig. 4.1 (a) Identify structures A to D. A B C D [2] (b) State the origins of structures A and D. [1] A B C D

9 © Hwa Chong Institution 2024 9744 H2 Biology / JC2 Preliminary Examinations / Paper 2 (c) Both coronavirus and influenza virus rely on a similar class of enzyme for their replication processes. Describe how the coronavirus produces viral progenies after entry into host cells. [4] (d) Suggest how a virus such as SARS-CoV can potentially result in outbreak of new viral diseases. [3] [Total: 10]

10 © Hwa Chong Institution 2024 9744 H2 Biology / JC2 Preliminary Examinations / Paper 2 QUESTION 5 Differential gene expression enables eukaryotic cells to synthesise the proteins required for normal function. (a) Describe how gene expression in eukaryotes can be downregulated at the chromatin level. [3] Fig. 5.1 shows how a mature mRNA can be reverse-transcribed to form complementary DNA (cDNA), which is subsequently amplified by PCR. Fig. 5.1 (b) Explain why RNA cannot act as a template for PCR amplification. [2] AAAAAA AAAAAA TTTTTT mature mRNA cDNA reverse transcription PCR amplification cells extraction of mRNA