EJC 2023 H2 9744 P3 (ans)

©EJC 2023 9744/03/J2H2PRELIM/2023 [Turn over EUNOIA JUNIOR COLLEGE JC2 Preliminary Examinations 2023 General Certificate of Education Advanced Level Higher 2 CANDIDATE NAME CIVICS GROUP 2 2 - REGISTRATION NUMBER H2 Biology Paper 3 Long Structured and Free-response Questions 9744/03 19 September 2023 2 hours Additional Materials: 12-page Answer Booklet READ THESE INSTRUCTIONS FIRST Write your name, civics group and registration number on all the work you hand in. Write your answers in dark blue or black pen. You may use an HB pencil for any diagrams or graphs. Do not use paper clips, highlighters, glue, or correction fluid/tape. Section A Answer all questions on the Question Paper. Section B Answer one question on the 12-page Answer Booklet provided. Write your answer to each part of the question on a fresh sheet of paper. The use of an approved scientific calculator is expected, where appropriate. The number of marks is given in brackets [ ] at the end of each question or part question. At the end of the examination, ensure that you submit both the Question Paper and Answer Booklet. This document consists of 12 printed pages. For Examiner’s Use Section A 1 2 3 Section B 4 OR 5 Total 75

2 ©EJC 2023 9744/03/J2H2PRELIM/2023 Section A Answer all questions on the Question Paper. 1 Scientists have produced structures known as virosomes, which are used in certain vaccines. Virosomes do not cause disease. Fig. 1.1 is a diagram of a section through a virosome used in some vaccines to protect against the influenza virus. Fig. 1.1 (a) (i) State the structural differences between a virosome and a virus. [2] Any 2 1. Virosome does not have any nucleic acids / genetic material whereas a virus does; 2. Virosome does not have a capsid / capsomeres whereas a virus does; 3. Virosome has a phospholipid bilayer as an envelope whereas some viruses like bacteriophages do not; 4. AVP (no nucleocapsid vs has nucleocapsid, no nucleoprotein vs has) R: virosome has haemagglutinin vs HIV has gp120 (ii) Explain how the structure of the virosome shown in Fig. 1.1 suggests that the central area of the virosome is aqueous. [2] 1. The phosphate head of the phospholipid is charged and hydrophilic; 2. and is facing/pointing towards the central area of the virosome. Thus, the central area of the virosome must be aqueous; OR 3. The hydrocarbon tails of the phospholipids are non-polar and hydrophobic; 4. and are pointing away from the central area of the virosome. Thus, the central area of the virosome must be aqueous;

3 ©EJC 2023 9744/03/J2H2PRELIM/2023 [Turn over (b) The glycoproteins haemagglutinin and neuraminidase found in the influenza virus are also found in the virosomes used in a vaccine against the influenza virus. Briefly explain why haemagglutinin is present in virosomes used in the vaccine for influenza. [3] 1. Haemagglutinin acts as a foreign / non-self antigen; 2. It will trigger/stimulate the primary immune response to provide artificial active immunity; (A: phagocytosis and antigen presentation to activate naïve T and B cells) 3. This will lead to the formation of memory cells ev entually; any two from: acts as a non -self / foreign, antigen ; triggers / stimulates, primary immune response or provides (artificial) active immunity ; (leads to) formation of antigen presenting cell ; A endocytosis / phagocytosis, to present antigen (by, macrophage neutrophil ) activates, B lymphocytes / T lymphocytes ; A clonal selection formation of memory cells ; Fig. 1.2 shows the antibody concentration in a patient’s serum after he was vaccinated with the virosome. Fig. 1.2 (c) (i) On Fig. 1.2, illustrate the antibody concentration the patient’s serum after he was exposed to an influenza virus with the same haemagglutinin and neuraminidase found on the virosome. [1] Shorter time for antibody appearance + s teeper gradient + higher peak for concentration of antibody virosome administered Time / days antibody concentration in serum / arbitrary units exposure to influenza virus

4 ©EJC 2023 9744/03/J2H2PRELIM/2023 (ii) Explain your answer to (c)(i). [3] 1. memory B cells are involved in the secondary immune response when re-exposed to the same haemagglutinin and neuraminidase; 2. These memory B cells undergo faster clonal expansion and differentiation into antibody-secreting plasma B cells ; (R: “rapid” because lack idea of comparison with primary immune response) 3. which will result in the faster production of greater concentration of antibodies (A: more antibodies); 4. N ote: Accept “for a longer period of time” as a point if it tallies with their graph. (d) (i) The white blood cells that produce antibodies originate from a stem cell. Identify the stem cells in the body that these white blood cells are derived from. [1] lymphoid stem cell; R: blood stem cell (ii) Describe the differentiation potential of these stem cells. [2] 1. These stem cells are multipotent; 2. They have the ability to differentiate into several related specialised blood cell types; (R: have the ability to differentiate into WBCs) (e) Due to the emergence of new strains of influenza virus, a new influenza vaccine has to be developed periodically. Other than mutations, explain how new strains of influenza virus can come about. [4] 1. New strains of influenza can come about as a result of antigenic shift; 2. This happens when two or more strains of influenza viruses infect the same host cell; 3. Reassortment of the different RNA segments occur resulting in new combination of viral RNA segments in a virion; 4. New combination of hemagglutinin and neuraminidase embedded on the viral envelope;

5 ©EJC 2023 9744/03/J2H2PRELIM/2023 [Turn over Fig. 1.3 shows a stage of protein synthesis during the reproductive cycle of influenza virus. This takes place in the cytosol of a human cell. Fig. 1.3 (f) (i) Name the stage of protein synthesis shown in Fig. 1.3. [1] Translation; R: elongation (ii) State the base sequence of the anticodon on structure D. [1] 3’ CUG 5’ / 5’ GUC 3’ Note to marker: can accept “GUC” without directionality, but remove from mark scheme! (iii) Explain the roles of structure A in the reproductive cycle of influenza virus. [3] 1. Structure A is viral mRNA; 2. It serves as the template for translation for the synthesis of viral proteins; 3. It also serves as the template for synthesis of viral genome; Note to marker: “viral” must appear in points 2 and 3. (iv) After the synthesis of structure C is completed, it will fold into a viral protein. Suggest if this viral protein is likely to be haemagglutinin or RNA -dependent RNA polymerase. Explain your answer. [2] 1. The viral protein is likely to be RNA-dependent RNA polymerase; 2. This is becaus e RNA -dependent RNA polymerase is synthesised by free ribosomes whereas haemagglutinin is synthesised by ribosomes on the rough endoplasmic reticulum;

6 ©EJC 2023 9744/03/J2H2PRELIM/2023 (g) In a human cell, proteins can undergo post-translational modifications. Explain the significance of such modifications. [2] Any 2: 1. The protein can be phosphorylated, which either activate / inactivate the protein; 2. The protein can be glycosylated whereby one or more sugar monomers are added, to form glycoproteins; 3. The protein can be ubiquitinated, whereby the addition of ubiquitin allows proteasomes to identify the protein for degradation; 4. R emoval of the inhibitory portions of the polypeptide chain