2012 RI Prelim Bio H1 P2_answers - RAFFLES INSTITUTION Higher 1 Biology Paper 1,2&3 Answers Paper 1 answers 1 2 3 4 5 6 7 8 9 10 D B B C D D B D A B 11

2012 RI Prelim Bio H1 P2_answers - RAFFLES INSTITUTION...

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[Turn over RAFFLES INSTITUTION Higher 1 Biology Paper 1,2 &3 Answers . Paper 1 answers: 1. D 11. B 21. A 2. B 12. B 22. B 3. B 13. C 23. D 4. C 14. A 24. A 5. D 15. D 25. B 6. D 16. C 26. D 7. B 17. B 27. B 8. D 18. C 28. D 9. A 19. C 29. A 10. B 20. C 30. D Paper 2 answers: Section A Answer all the questions in this section. 1 In an experiment to study ATP synthesis in plants, chloroplasts are isolated, and the pH levels in the various compartments are monitored. The graph below shows the results of the experiment. (a) Explain the changes in pH seen in Fig.1.1 upon illumination. [3] Illumination of chloroplasts causes the excitation of the electrons from the reaction centre. This initiates the electrons flow down the ETC, energy lost is used to pump H+ from the stroma into the thylakoid. Hence the increase in pH in the stroma and the decrease in pH (increase in H+) in the thylakoid space © RI 2012 Preliminary Examination 8875/02 Fig.1.1 pH Light
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For Examiner’s Use 2 (b) Describe a similarity and a difference in the production of ATP in chloroplasts and in mitochondria. [2] Similarity 1. Flow of electron down the electron transport chain of progressively increasing electronegativity. 2. Generation of proton motive force / electrochemical / H + gradient 3. Diffusion of H + from through ATP synthase complex , energy used for the phosphorylation of ADP to ATP (ref to chemiosmosis, but R:just chemiosmosis without description) Difference Photophosphorylation Oxidative phosphorylation Electron donor Reaction centre chlorophyll a / water Reduced coenzyme, NADH/FADH Final electron acceptor NADP Molecular Oxygen Source of energy for phosphor ylation Light Oxidation of glucose / NADH / FADH (to be discussed) *Direction of H + pumped Pumped from stroma to thylakoid space Pumped from matrix to intermembranal space *Direction of H+ diffuse from thylakoid space to stroma from intermembranal space to matrix (c) According to the endosymbiotic theory, mitochondria and chloroplasts were originally prokaryotic cells that were engulfed by an ancestral eukaryotic cell. State two structural features of the two organelles that provide evidence to support this theory. [2] Circular DNA 70S ribosomes double membrane © RI 2012 Preliminary Examination 8875/02
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For Examiner’s Use 3 Molecule X forms a pore in the phospholipid bilayer of mitochondria as shown in the Fig.1.2. Fig.1.2 (d) Explain how the presence of molecule X might affect the synthesis of ATP in isolated mitochondria. [3] no ATP synthesis Allows H + to diffuse down a concentration gradient through the pore and prevents the generation of H+ / electrochemical gradient (e) In plants, yeasts and bacteria, anaerobic respiration results in the production of alcohol and carbon dioxide, a process that is exploited by both the brewing and the baking industries.
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