2021 EJC Promo JC1 P2 Bio (Q)

©EJC 2021 9744/02/J1H2/Promo/2021 Turn over EUNOIA JUNIOR COLLEGE JC1 Promotional Examinations 2021 General Certificate of Education Advanced Level Higher 2 CANDIDATE NAME CIVICS GROUP 2 1 - REGISTRATION NUMBER H2 Biology Paper 2 Structured & Free Response Questions 9744 05 October 2021 2 hours Additional Materials: 12-page Answer Booklet. READ THESE INSTRUCTIONS FIRST Write your name, civics group and registration number in the spaces at the top of this page. Write 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. Section A Answer all questions in the spaces provided on the Question Paper. Section B Answer all questions in the 12-page Answer Booklet. 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. This document consists of 17 printed pages and 1 blank page. For Examiner’s Use Section A 1 2 3 4 5 6 7 Section B 8 Total 80

2 9744/02/J1H2/Promo/2021 Section A 1 Fats are usually stored as oil in the seeds of the plants and occasionally in the fleshy part of the fruit, as in the olive and the oil palm. The oil is a reserve of high -energy food for use by the germinating seed for growth of the embryo. The sunflower seed is actually the fruit of the sunflower (Helianthus annuus) and may contain about 51% oil. Fig. 1.1 shows a triglyceride molecule found in sunflower oil. (a) On Fig. 1.1, circle an ester bond. [1] (b) Sunflower oil can be used to make biodiesel. During the process, the fatty acids in the triglyceride react with methanol to form fatty acid methyl esters that are liquid products. The other component of the original triglyceride molecule forms another liquid product that is denser than the methyl esters. Name the component of the molecule seen in Fig. 1.1 that forms this denser liquid. ……………………………………………………………………………………………………… [1] (c) Table 1.1 shows the melting points of the three different fatty acid methyl esters. Table 1.1 fatty acid methyl ester formula melting point / oC methyl linoleate C19H34O2 methyl linolenate C19H32O2 - 55.0 methyl oleate C19H36O2 - 20.0 Fig. 1.1

3 9744/02/J1H2/Promo/2021 Turn over (i) Complete Table 1.1 with one possible value for the melting point of methyl linoleate. [1] (ii) Suggest one way the structure of fatty acids found in butter might differ from the fatty acid that forms methyl oleate. …………………………………………………………………………………………………………. ……………………………………………………………………………………………………... [1] (d) Living organisms have many uses for trigly cerides, one of which is the production of phospholipids. Describe how the roles of triglycerides and phospholipids differ in cells. ………………………………………………………………………………………………………… …............................................................................................................................................. ................................................................................................................................................. ............................................................................................................................................ [2] (e) Explain why phospholipids are able to form bilayers in a cell. ………………………………………………………………………………………………………… …............................................................................................................................................. ................................................................................................................................................. ............................................................................................................................................ [2] [Total: 8]

4 9744/02/J1H2/Promo/2021 2 Phosphatases are enzymes that catalyse the removal of phosphate groups from organic compounds. A student investigated the effect of substrate concentration on the rate of the reaction catalysed by an acid phosphatase (enzyme A). The results are shown in Fig. 2.1. Fig. 2.1 (a) (i) On Fig. 2.1, show how Km for enzyme A is derived. [1] (ii) State the Km value. ……………………………………………………………………………………………………… [1] (b) The student investigated a different phosphatase enzyme (enzyme B) and found the value of Km to be higher than that of enzyme A. Explain the difference between the values of Km for these two phosphatase enzymes. ………………………………………………………………………………………………………… …............................................................................................................................................. ................................................................................................................................................. ............................................................................................................................................ [2]

5 9744/02/J1H2/Promo/2021 Turn over (c) The student repeated the investigation on enzyme A with a competitive inhibitor. The same concentrations of substrate were used as before, but a competitive inhibitor was added to each reaction mixture. The same concentration of the inhibitor was used in each reaction mixture. The student found that V max was the same as before, but Km was higher. Explain how the addition of the competitive inhibitor results in the same value for Vmax but a higher value for Km. ................................................................................................................................................. ................................................................................................................................................. ................................................................................................................................................. ................................................................................................................................................. ................................................................................................................................................. ................................................................................................................................................. ................................................................................................................................................. ............................................................................................................................................ [4] [Total: 8]

6 9744/02/J1H2/Promo/2021 3 Fig. 3.1 shows a transmission electron micrograph of a replication bubble. Fig. 3.1 (a) In eukaryotic cells, there are many sites of origin of replication for each DNA molecule. (i) Explain an advantage of having many sites of origin of replication, rather than only one site. ................................................................................................................................................. .......................