NJC 2023 H2 Biology Prelim P2 Ans

©NJC 2023 9744/02/SH2/H2/Biology/Preliminary Examination [Turn over NATIONAL JUNIOR COLLEGE, SINGAPORE Senior High 2 Preliminary Examination Higher 2 CANDIDATE NAME BIOLOGY CLASS 2bi2_____ REGISTRATION NUMBER Biology Paper 2: Structured Questions Candidates answer on the Question Paper. No Additional Materials are required. 9744/02 24 August 2023 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. 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 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 1 /10 2 /9 3 /11 4 /11 5 /9 6 /12 7 /10 8 /8 9 /10 10 /5 11 /5 Total /100 This document consists of 27 printed pages and 1 blank page.

©NJC 2023 9744/02/SH2/H2/Biology/Preliminary Examination 2 Section A Answer all the questions in this section. 1 Triglycerides are transported via lipoproteins such as low-density lipoproteins (LDL). LDL are taken up by target cells as shown in Fig. 1.1. Fig. 1.1 (a) Name the structures labelled A in Fig. 1.1. Ribosomes; [1] (b) Explain the roles of B in the synthesis of LDL receptor. chemically modifies the LDL receptors (e.g. glycosylation); packages LDL receptors the into transport vesicles to be targeted to the plasma membrane for insertion into membrane; [2]

©NJC 2023 9744/02/SH2/H2/Biology/Preliminary Examination [Turn over 3 (c) With reference to Fig. 1.1, describe how an LDL particle is taken up by a target cell. Ligands on LDP particle bind to LDL receptor on surface of target cell; Target cell forms an invagination of the cell surface membrane; An endosome / vesicle containing the LDL particle is formed within the cell; [3] Lipoproteins are made up of proteins and lipids. Their function is to transport cholesterol, triglycerides, and other lipids in the bloodstream. Fig. 1.2 represents the structure of a lipoprotein. Fig. 1.2 (d) (i) With reference to Fig. 1.2, describe the arrangement of phospholipids in lipoproteins. Phospholipids are arranged in a monolayer / single layer; Hydrophobic hydrocarbon tails face inwards while the hydrophilic phosphate heads face outwards; [2] (ii) Suggest why lipoproteins are needed to transport cholesterol, triglycerides, and other lipids in the bloodstream. Triglycerides are hydrophobic in nature and cannot interact with the aqueous medium in the blood; Ref. to phospholipids as amphipathic; Their tails interact with triglycerides within its interior