CJC 2023 JC2 Bio P2 (Ans)

NAME: ___________________________________________ CLASS: _________ INDEX: __________ CATHOLIC JUNIOR COLLEGE JC2 PRELIMINARY EXAMINATION Higher 2 BIOLOGY 9744/02 STRUCTURED QUESTIONS 21 August 2023 2 hours READ THESE INSTRUCTIONS FIRST Write your name (as per NRIC), class, and index number on all the work you hand in. Write in dark blue or black pen on both sides of the paper. [PILOT FRIXION ERASABLE PENS ARE NOT ALLOWED] You may use a soft pencil for any diagrams, graphs or rough working. Do not use staples, paper clips, highlighters, glue or correction fluid. The number of marks is given in brackets [ ] at the end of each question or part question. There are 11 questions with multiple subparts in this paper. Answer all questions in the spaces provided on the Question Paper. This document consists of 34 printed pages and 0 blank pages. [ T u r n o v e r ] For Examiner’s Use Total 100 1 2 3 4 5 6 7 8 9 10 11 Suggested Answers

2 2023 Prelim/ 9744/ 02 Answer all questions 1 (a) Thermotoga maritima is a hyperthermophilic species of bacterium that lives in hot springs and thermal vents associated with volcanic activities. The bacteria can survive in waters at 80°C. Two amino acids found in the primary structure of an enzyme in the bacterium are shown below: Fig. 1.1 (i) Part of the sequence of amino acids in the enzyme consist of Cys-His. Draw a labelled diagram of the dipeptide that would result during this condensation. [2] peptide linkage [2] 1. Correct illustration of condensation (i.e. condensation of C α–COOH of cysteine and –NH2 of histidine rather than the R groups) with peptide bond clearly labelled 2. Proper orientation of the dipeptide such that the N- and C-terminus is discernible, N- Cysteine, C-Histidine. C N C COOH NH N H

3 2023 Prelim/ 9744/ 02 (ii) “Cysteine is found to be more common than most other amino acids in the Thermotoga maritima enzyme compared to those found in other species”. Suggest why this may be so. …………………………………………………………………………………………………………….. …………………………………………………………………………………………………………….. ………..…………………………………………………………………………………………………… ………………….……………………………………………………………………………………… [2] 1. Cysteine is the only amino acid that has an –SH R group (explains more common than most other amino acids); capable of forming disufide bridges between their R-groups which are strong covalent bonds. 2. Cov