2024 NJC H2 Bio P2 MS

©NJC 2024 9744/02/SH2 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 2 Structured Questions Candidates answer on the Question Paper. No Additional Materials are required. 9744/02 27 August 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. 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 Section A 1 /10 2 /10 3 /10 4 /10 5 /10 6 /10 7 /10 8 /10 9 /10 10 /5 11 /5

2 ©NJC 2024 9744/02/SH2 Preliminar y Examination Total /100 This document consists of 26 printed pages and 2 blank pages.

3 ©NJC 2024 9744/02/SH2 Preliminary Examination [Turn over Answer all the questions. 1 Fig. 1.1 is an electronmicrograph of part of a human liver cell that contains many glycogen granules. Fig. 1.1 (a) Structures A and B are interconnected sub-compartments. Name and state the role of structures A and B. name role A smooth endoplasmic reticulum; site of lipid synthesis; involved in drug detoxification; B rough endoplasmic reticulum (reject ribosomes on rough endoplasmic reticulum); involved in the synthesis of secretory proteins / membranal proteins; addition of carbohydrates to form glycoproteins / modifying of proteins; proteins synthesised are transported within vesicles to the Golgi body; [4] (b) Explain why it is important for a human liver cell to contain many glycogen granules. Serves as a form of energy storage (reject long-term/short-term if never specify comparison); Maintain blood glucose levels during times of high energy demands / stress / fasting;

4 ©NJC 2024 9744/02/SH2 Preliminar y Examination [2] Isolation membranes derived from structure A play important role in degradation of unwanted cytoplasm components. Fig. 1.2 shows the steps involved in the degradation of unwanted cytoplasm components. Fig. 1.2 (c) With reference to Fig. 1.2, describe how the unwanted cytoplasm components are degraded. The isolation membrane expands to enclose the unwanted cytoplas m components such as mitochondrion; An autophagosome is formed after pore closure; Lysosome fuses with the autophagosome to form an autolysosome; Hydrolytic enzymes in the autolysosome catalyse the degradation of the inner membrane / the unwanted cytoplasm components; This process is known as autophagy;

5 ©NJC 2024 9744/02/SH2 Preliminary Examination [Turn over [4] [Total: 10]

6 ©NJC 2024 9744/02/SH2 Preliminar y Examination 2 Fig. 2.1 shows the components of a storage molecule that is widely distributed in plants. A B Fig. 2.1 (a) Identify the components A and B. A amylopectin; B amylose; [2] (b) The presence of branches is a key structural feature of component A. Explain how this structural feature enables the function of component A. Branching decreases the ability of the chains to get together with one another and increases the binding of water molecules to the chains; This allows rapid release of glucose molecules from the many en d s / r a p i d h y d r o l y s i s o f component A at the many ends for use in cellular respiration; Branching also makes component A m o r e c o m p a c t , c o n t a i n i n g m o r e g l u c o s e u n i t s w h i l e taking the least possible space, and is therefore ideal for its function as a storage molecule; [2]

7 ©NJC 2024 9744/02/SH2 Preliminary Examination [Turn over Fig. 2.2 shows two types of glucose that are found in plants. Fig. 2.2 (c) With reference to Fig. 2.2, draw a labelled diagram in the spac e provided to show how two glucose molecules react to form a branch point in component A. two α-glucose drawn and labelled correctly; 1-6 α-glycosidic bond drawn and labelled correctly; formation of one water molecule / condensation indicated; [3] (d) Glycolipids are generally found on the extracellular face of the eukaryotic cell surface membrane. Describe the roles of glycolipids in eukaryotic cell surface membrane. The carbohydrate group of glycolipids serves as a recognition s ite for other molecules and cells; This forms the basis of cell-cell recognition (crucial to the i mmune response) / cell-cell adhesion (to form tissues) / cell signalling; They help in determining the blood group of an individual;

8 ©NJC 2024 9744/02/SH2 Preliminar y Examination Formation of myelin sheath in neurones; They maintain the stability of the cell membrane; [3] [Total: 10] 3 (a) Fig. 3.1 shows the process of DNA replication. Fig. 3.1 ( i ) On Fig. 3.1, ● label a leading strand (1m) and a lagging strand (1m) ● draw an arrow (1m) to show the direction of movement of the replication fork. [3] (ii) Name the molecules A and B. A B leading strand lagging strand

9 ©NJC 2024 9744/02/SH2 Preliminary Examination [Turn over A helicase; B DNA polymerase; [2] (iii) Describe how a mutation in the gene coding for molecule B can affect its function in DNA replication. ref to nucleotide-pair substitution / addition / deletion; ref to effect (e.g. missense / nonsense mutation) on mRNA produced; ref to effect (e.g. change in active site of enzyme) on protein produced; ref to function in DNA replication e.g. unable to polymerise / proof-read; (accept loss or gain of function) [3] (b) Dideoxycytosine triphosphate (ddCTP) can bind to the active site of molecule B, in a similar way to deoxycytosine triphosphate (dCTP). Fig. 3.2 shows the structure of dCTP and ddCTP. Fig. 3.2

10 ©NJC 2024 9744/02/SH2 Preliminar y Examination In an in vitro DNA replication reaction mixture, ddCTP was added together wit h deoxyribonucleotides. Suggest how the addition of ddCTP would affect DNA replication. ddCTP competes with dCTP for the active site of DNA polymerase and forms a phospho(di)ester bond with 3’ hydroxyl group of the daughter strand; ddCTP lacks a 3’ hydroxyl group on the deoxyribose / pentose sugar; The incorporated ddCTP cannot form a phospho(di)ester bond with incoming dNTPs; DNA replication is terminated prematurely; [2] [Total: 10] 4 E p s t e i n - B a r r v i r u s ( E B V ) w a s t h e f i r s t v i r u s k n o w n t o c a u s e h u man cancer. Human B lymphocytes are the host cells of EBV infection. Fig. 4.1 shows the structure of EBV. Fig. 4.1 (a) (i) Identify the structures A and B. A (envelope) glycoprotein; B envelope / membrane / lipid bilayer; [2] A B C double-stranded DNA