SAJC 2023 H2 BIO P2 ANS

Civics Group Index Number Name (use BLOCK LETTERS) ST. ANDREW’S JUNIOR COLLEGE 2023 JC2 PRELIMINARY EXAMINATIONS H2 BIOLOGY 9744/2 Paper 2 Monday 28 th August 2023 2 hours Materials: Question Paper READ THESE INSTRUCTIONS FIRST Write your name, civics group and index number on all the work you hand in. Write in dark blue or black pen on both sides of the paper. You may use a soft pencil for any diagram, graph or rough working. Do not use staples, paper clips, highlighters, glue or correction fluid. Answer all questions. Write your answers in the spaces provided on the question paper. The number of marks is given in brackets [ ] at the end of each question or part question. For Examiners’ Use 1 /13 2 /10 3 /12 4 /12 5 /14 6 /9 7 /11 8 /9 9 /5 10 /5 Total /100 This document consists of xx printed pages and x blank page. [Turn over H2

QUESTION 1 Fig. 1.1 is an electron micrograph that shows part of a eukaryotic cell. Fig. 1.1

(a) Organelle B is made of two types of molecules. (i) Name the molecules in organelle B and state the process and location where each molecule is synthesized, by completing the table below: Organelle B Molecule 1 Molecule 2 1 Name ribosomal {RNA / ribonucleic acid(s)} protein(s) 2 Process transcription translation 3 Location nucleolus cytoplasm (ii) Identify the organelle B in Fig. 1.1 and state one function of this organelle. …………………………………………..……………………………………………………………[2] 1 Ribosome; Function : any one 2 Sites of {translation of mRNA into polypeptides / synthesis of protein} ; 3 Ribosomes contain binding sites for both tRNA and mRNA ; 4 Peptidyl transferase activity present in the large ribosomal subunit catalyse the formation of peptide bonds between amino acid; (b) Collagen is a protein produced by cells and is the most common structural protein, due to its high tensile strength, in vertebrates. (i) To form collagen, many of the amino acids such as proline and lysine are modified by the addition of a hydroxyl group on its side chain to form hydroxyproline and hydroxylysine residues, respectively. Vitamin C is necessary in aiding this conversion of proline and lysine to hydroxyproline and hydroxylysine. Vitamin C works by preventing the inactivation of two key enzymes, lysyl and prolyl hydroxylas, in collagen biosynthesis. Fig. 1.2 shows the synthesis of collagen. Production of tropocollagen starts with procollagen Procollagen, once secreted outside the cell, will be cleaved at C and N terminus to form tropocollagen.

Fig. 1.2 Describe how the procollagen is synthesized and secreted out of the cell to be assembled into collagen. ………………………………………………………………………………………………[6] (Procollagen is made up of 3 polypeptide chains) 1 Each polypeptide is first synthesized by the ribosomes on the rER; [Reject: polypeptide folds into