2024 NJC H2 Bio P3 MS

©NJC 2024 9744/03/Preliminary Examination [Turn over H NATIONAL JUNIOR COLLEGE, SINGAPORE Senior High 2 Preliminary Examination Higher 2 CANDIDATE NAME BIOLOGY CLASS 2bi2_____ R E G I S T R A T I O N NUMBER Biology Paper 3 Long Structured and Free-response Questions Candidates answer on the Question Paper. Additional Materials: Answer Booklet 9744/03 13 September 2024 2 hours READ THESE INSTRUCTIONS FIRST Write your name, Biology class and registration number on all the work you hand in. Write in dark blue or black pen. You may use an HB for any diagrams or graphs. Do not use staples, paper clips, glue or correction fluid. Section A Answer all questions in the spaces provided on the Question Paper. Section B Answer any one question in the separate Answer Booklet. The use of an approved scientific calculator is expected, where appropriate. You may lose marks if you do not show your workings or if you do not use appropriate units. The number of marks is given in the brackets [ ] at the end of each question or part of question. For Examiner’s Use Section A 1 /30 2 /10 3 /10 Section B 4 or 5 /25 Total /75

2 ©NJC 2024 9744/03/Preliminar y Examination This document consists of 15 printed pages and 1 blank page.

3 ©NJC 2024 9744/03/Preliminary Examination [Turn over Section A Answer all the questions in this section. 1 Collagen is a key structural protein found in various tissues t hroughout the body. Its measurements can vary significantly depending on the type a nd function of the collagen. Type I collagen is the most abundant form. Fig. 1.1 shows the structure of type 1 collagen fibrils. Fig. 1.1 (a) (i) Describe the molecular structure of collagen and explain how its structure relates to its function. LO 1(o) Answer: Describe D1. Ref to repeated Gly–X–Y m o t i f + X i s o f t e n proline, Y is often hydroxyproline; D2. Ref to 1000 amino acids forming left-handed helix; D3. Ref to three polypeptide chains supercoiling to form tropocollagen; Explain [5]

4 ©NJC 2024 9744/03/Preliminar y Examination E1. Ref to glycine allowing tight-packing of helix + increasing strength of tropocollagen; E2. Ref to proline/ hydroxyproline’s bulky structure + contributing to rigidity (limit rotation of peptide chain) and hence stability of tropocollagen; E3. Ref to extensive hydrogen bonding between –NH and –C=O of peptide bonds in adjacent polypeptide chains/ adjacent tropocollagen molecules + increasing tensile strength of tendons/ cartilages; E4. Ref to covalent cross-linking between lysine at the ends of tropocollagen molecules + increasing tensile strength of/ distributing pressure across tendons/ cartilages; E5. Ref to staggered arrangement + minimising points of weaknesses; E6. Ref to microfibrils/fibrils forming fibres + increasing tensile strength increasing tensile strength of tendons/ cartilages; E7. Ref to hierarchical