2024 ASRJC JC2 H2 Biology Prelim P3 MS

ASRJC BIOLOGY DEPT 9744//2024/J2PRELIM/P3 [Turn over H2 ANDERSON SERANGOON JUNIOR COLLEGE HIGHER 2 ANSWERS 2024 JC2 PRELIMINARY EXAMINATION CANDIDATE NAME CLASS INDEX NUMBER BIOLOGY 9744/03 PAPER 3 LONG STRUCTURED AND FREE RESPONSE QUESTIONS Candidates answer on the Question Paper. No Additional Materials are required. 10 SEPTEMBER 2024 TUESDAY 2 HOURS READ THESE INSTRUCTIONS FIRST Write your name and class on all the work you hand in. Write in dark blue or black pen. You may use an HB pencil for any diagrams or graph Do not use paper clips, highlighters, glue or correction fluid. Section A Answer all questions in the spaces provided on the Question Paper. Section B Answer any one question 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 working or if you do not use appropriate units. At the end of the examination, fasten all your work securely together. The number of marks is given in brackets [ ] at the end of each question or part question. This document consists of 13 printed pages and 1 blank page For Examiner’s Use 1 / 30 2 / 10 3 / 10 4 / 5 / 25 Total / 75

2 ASRJC BIOLOGY DEPT 9744//2024/J2PRELIM/P3 Section A Answer all the questions in this section. 1 Malaria is a disease caused by the Plasmodium parasite. There are four species of the Plasmodium parasite, of which Plasmodium falciparum is responsible for most of the deaths from this disease. Fig. 1.1 shows part of the life cycle of P. falciparum, which requires two hosts. A female mosquito carrying P. falciparum injects the parasite, in a form known as a sporozoite, into the bloodstream of an uninfected person. The P. falciparum parasite multiplies in a liver cell before emerging as a different form, known as a merozoite, wrapped in the liver cell surface membrane. It enters a red blood cell and multiplies before causing the rupture of the red blood cell, releasing more parasites. Fig. 1.1 A. B.

3 ASRJC BIOLOGY DEPT 9744//2024/J2PRELIM/P3 [Turn over (a) State two features, visible in Fig. 1.1B, that indicate that P. falciparum is eukaryotic. 1. Presence of membrane bound organelle / compartmentalisation via membranes Named example 2. Presence of nucleus / nuclear envelope 3. Presence of (membrane bound) food vacuole 4. Presence of a mitochondrion [2] (b) To control the spread of malaria, re search has been directed towards the development of a malarial vaccine. Much of this research relies on the fact that P. falciparum has different forms in its life cycle. During a trial, researchers were able to extract both the sporozoite form (the form injected by mosquitoes) and the merozoite form (the form that leaves the liver , before entering red blood cells) of P. falciparum. With reference to Fig. 1.1, su ggest why researchers chose to use the sporozoite form of P. falciparum instead of the merozoite form in the malarial vaccine. 1. idea of sporozoite of parasite not wrapped in liver surface membrane / merozite form is wrapped in liver cell surface membrane / in red blood cell AND 2. idea of antigens in the sporozoite form can be more easily exposed OR antigens in merozoites cannot be exposed to immune system to stimulate immune system (during vaccination) / for killing by immune cells during actual an actual infection OR 3. sporozoite form has not multiplied compared to merozoite form which would have multiplied in numbers (in the liver ) / prevent sporozoite from multiplying AND 4. immune cells has less parasites to destroy/ limit spread within the body 3. vaccination against form leaving liver would, not protect against liver invasion / still cause liver damage ( since sporozoite form is not quickly removed by the immune cells during actual infection) / [2]

4 ASRJC BIOLOGY DEPT 9744//2024/J2PRELIM/P3 (c) In another trial, a naturally occurring mutant form of P. falciparum parasite discovered in Africa was tested for use as a vaccine against malaria. The mutant parasite develops normally in mosquitos. In humans, however, the mutant P. falciparum infects liver cells but does not multiply and cannot enter red blood cells. An investigation was conducted to test this vaccine using mice. Four test groups of 10 mice each were injected (inoculated) with mutant P. falciparum cells, followed by booster doses every six months after the first inoculation. The effectiveness of the vaccine was then tested by injecting non-mutant (wild type) P. falciparum cells into all the mice. Table 1.1 shows the results of investigation. Table 1.1 number of mutant P. falciparum cells given to mice percentage of mice not infected by non-mutant (wild type) P. falciparum test group first inoculation first booster inoculation second booster inoculation 1 0 0 0 0 Means 100% infected 2 50 000 25 000 25 000 100 Means 0% infected 3 10 000 10 000 10 000 100 Means 0% infected 4 10 000 10 000 0 70 Means 30% infected (i) Evaluate whether the results of this investigation is sufficient for researchers to recommend an effective vaccination plan against malaria. Sufficient because results show 1. Gp 1 ( not inoculated) 0% not infected/ 100% infected vs Gp 2 /3/4 ( inoculated) : 100% not infected / 0% infected 2. Inoculating with higher amount of mutant cells ( quote either 50000, 25000 ) gives the same just 3 time of 10 000 mutant plasmodium cells ( test group 3) provided same immunity/ same effectiveness as giving 50 000, 25 000 , 25000 mutant cells ( test group 2) : quote values- both resulted in 100% of mice not infected by wild type parasite 3. 2nd Booster inoculation is needed for vaccine to remain effective as shown in test group 4 where only ( accept only) 70% of mice were not infected without a second booster compared to test group 3 of 100% [4]

5 ASRJC BIOLOGY DEPT 9744//2024/J2PRELIM/P3 [Turn over Limitations of the investigation (any 2) 1. Vaccine was made using P. falciparum, may not be effective against other ( 3) species of plasmodium that cause malaria/ 2. Vaccine was made using made using P. falciparum from Africa, may not be effective against people in other countries due to different genetic makeup in different people 3. No information about side effects of vaccine 4. Done in mice, do not know effects in humans / need for human trial Reject merely saying mice versus humans / accept not tested for use in humans 5. No information o n mice, same age/ species which may have different immune systems ( must relate to immune system) 6. Small sample size of 10 mice (ii) Volunteers who were injected with killed mutant P. falciparum cells produced antibodies, which provided some protection against malaria. Outline the events that occur following injection of the killed mutant P. falciparum, which lead to the eventual production of antibodies. At