2017 HCI H2 Biology Prelims Paper 3 Questions

© Hwa Chong Institution 2017 9744 H2 Biology / JC2 Preliminary Examinations / Paper 3 HWA CHONG INSTITUTION JC2 Preliminary Examinations Higher 2 CANDIDATE NAME CT GROUP 16S7 ___ CENTRE NUMBER INDEX NUMBER BIOLOGY Paper 3 Long Structured and Free-response Questions No Additional Materials are required. 9744/03 13 September 2017 2 hours INSTRUCTIONS TO CANDIDATES There are four question booklets (I to IV) to this paper. Write your name, CT group, Centre number and index number in the spaces provided at the top of this cover page, and your name and CT group on the lines provided at the top of the cover page of Booklets II, III and IV. SECTION A This section contains three structured questions. Answer all parts in the spaces provided on the question paper. SECTION B This section contains two free-response questions. Answer any one question. Your answer must be in continuous prose, where appropriate. INFORMATION FOR CANDIDATES 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. The number of marks is given in brackets [ ] at the end of each question or part question. You are reminded of the need for good English and clear presentation in your answers. This document consists of 19 printed pages and 5 blank pages. For Examiners' Use 1 / 25 2 / 10 3 / 15 4 or 5 / 25 Final Mark / 75

2 © Hwa Chong Institution 2017 9744 H2 Biology / JC2 Preliminary Examinations / Paper 3 BOOKLET I SECTION A QUESTION 1 Plants harvest light energy from the sun for photosynthesis, producing biomass that is used as food. Such biomass can also be used as ‘biofuels’, which include wood, ethanol, biodiesel and biogas. Biofuels offer plant-based solutions to the Earth's growing energy problems. Oats and wheat, commonly grown in temperate regions, are C3 plants. Most plants are C3 plants and are so-called because their first photosynthetic product is a three carbon compound. Corn, sorghum and sugarcane are C4 plants. They are common food crops of tropical regions. The enzyme ribulose bisphosphate carboxylase oxygenase (rubisco) catalyses the fixation of carbon dioxide in the Calvin cycle and is used by both C3 and C4 plants. Each molecule of rubisco is made up of eight large polypeptides and eight small polypeptides. Fig. 1.1 shows a side view of the molecule. Fig. 1.1 (a) (i) State why rubisco is said to have quaternary structure. [1] (a)(ii) Explain what makes a molecule such as rubisco soluble. [2] small polypeptide large polypeptide

3 © Hwa Chong Institution 2017 9744 H2 Biology / JC2 Preliminary Examinations / Paper 3 (b) In the absence of light, rubisco changes shape from an active form to an inactive form. Explain why rubisco does not need to be in an active form in the absence of light. [3] (c) The active sites of rubisco accept ribulose bisphosphate (RuBP) and either carbon dioxide or oxygen and can catalyse the two reactions shown: either RuBP + CO2  unstable intermediate compound  2GP (PGA) or RuBP + 2O2  unstable intermediate compound  GP (PGA) + 2CO2 Explain the consequences to the plant of the reaction involving oxygen. [3]

4 © Hwa Chong Institution 2017 9744 H2 Biology / JC2 Preliminary Examinations / Paper 3 Fig. 1.2 shows the temperatures and carbon dioxide concentrations at which growth of C3 or C4 plants are favoured, based on the yield of photosynthesis. Fig. 1.2 The annual mean carbon dioxide concentration measured at Mauna Loa Baseline Atmospheric Observatory, Hawaii, has increased over the last 50 years to 404.21 ppm in 2016. (d) With reference to Fig. 1.2, predict whether C3 or C4 plants are favoured in the context of global warming in the tropics. Explain how these plants are better adapted physiologically. [5]

5 © Hwa Chong Institution 2017 9744 H2 Biology / JC2 Preliminary Examinations / Paper 3 Biofuels have been around as long as cars have. At the start of the 20th century, Henry Ford planned to fuel his Model Ts with ethanol, and early diesel engines were shown to run on peanut oil. Discoveries of huge petroleum deposits kept petrol and diesel cheap for decades, however, and biofuels were largely forgotten. With the recent rise in oil prices, along with growing concern about global warming caused by carbon dioxide emissions, biofuels have been regaining popularity. Corn is a crop grown in the ‘Corn Belt’ of the United States Midwest for food and biofuel. Fig. 1.3 shows the industrial process of manufacturing ethanol from corn starch. Ethanol can be mixed with petrol to make gasohol. Fig. 1.3 (e) (i) Describe how yeast converts glucose to ethanol. [2] (ii) Explain why it may be better in the long term to use ethanol made from corn starch, rather than petrol, as a fuel for cars. [2]

6 © Hwa Chong Institution 2017 9744 H2 Biology / JC2 Preliminary Examinations / Paper 3 Transport in Britain accounted for 21% of all greenhouse gas emissions in 2007. In order to reduce greenhouse gas emissions, the UK Government has set a target of 10% of transport energy to come from sustainable sources by 2020. Biofuels, including biodiesel, are expected to provide a significant part of this 10%. Reliance on biofuels is controversial for the following reasons:  Some carbon dioxide is still released because energy is used during the production (cultivation, harvesting, processing) and distribution of biofuels.  Large areas of land may need to be taken out of food production to grow the crops. It is estimated that all such land in the UK would only meet about 10% of its total diesel needs.  The change in land use, such as from tropical rainforest to palm plantation, may release large amounts of carbon dioxide. Table 1.1 is an a ssessment of the carbon dioxide released during the cultivation, processing and distribution of plant-derived biodiesel as well as the annual emissions from any change of land use, assuming these are spread over 20 years. In Britain all diesel, now must include 3.3% biodiesel. As Table 1.1 shows, there is a wide range of sources. Table 1.1 crop country grams carbon dioxide equivalent released / MJ biodiesel produced emissions due to change of land use emissions from cultivation, processing and distribution existing crop land grassland forest oilseed rape UK 0 154 583 79 soy Brazil 0 683 2466 71 soy USA 0 122 1127 53 palm Indonesia 0 127 224 41 palm Malaysia 0 57 176 41 (f) (i) With reference to Table 1.1, suggest the source of biodiesel chosen by an oil company if reduction of greenhouse gas emissions were the sole criterion. [1] (g)(ii) Explain your answer to (f)(i). [2]

7 © Hwa Chong Institution 2017 9744 H2 Biology / JC2 Preliminary Examinations / Paper 3 (g) Identify two criteria, apart from cost, that should also be considered in choosing a source of biodiesel. Explain the significance of each criterion. [4] [Total: 25]

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