2020 EJC Promo JC1 P2 Bio (A)

©EJC 2020 9744/02/J1H2PROMO/2020 [Turn over EUNOIA JUNIOR COLLEGE JC1 Promotional Examinations 2020 General Certificate of Education Advanced Level Higher 2 CANDIDATE NAME ANSWER KEY CIVICS GROUP 2 0 - REGISTRATION NUMBER H2 Biology Paper 2 Structured Questions & Free Response Questions 9744/02 02 October 2020 2 hours Candidates are to answer questions in Section A in this question booklet. Candidates are to answer questions in Section B in the answer booklet provided. Additional Materials: 8-page Answer Booklet READ THESE INSTRUCTIONS FIRST Write your name, civics group and registration number on all the work you hand in. There are two sections in this paper, Section A and Section B. You are advised to plan your time appropriately to complete both Sections. Answer all questions. Write in dark blue or black pen on both sides of the paper. You may use an HB pencil for any diagrams or graphs. Do not use paper clips, highlighters, glue, or correction tape/fluid. 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. This document consists of 16 printed pages and 1 blank page. For Examiner’s Use 1 2 3 4 5 6 7 8 Total 80

2 ©EJC 2020 9744/02/J1H2PROMO/2020 For Examiner’s Use Section A Answer all the questions in this section. 1 Emperor penguins are the only species of penguin that breed during the Antarctic winter and they may stand still for multiple days to incubate their eggs. In order t o survive in freezing temperatures, the feet of emperor penguins contain a high percentage of unsaturated fats. (a) Explain the significance of unsaturated fatty acids (fatty acid tails) in cell membranes. [2] 1. Presence of C=C bonds causes kinks in unsaturated fatty acid tails [R: unsaturated fats] of phospholipids [R: kinks in membrane]; 2. This prevents close packing of phospholipids at low temperatures , reducing hydrophobic interactions between fatty acid tails, thus maintaining membrane fluidity [R: increasing fluidity] OR preventing cell membranes [R: unsaturated fatty acid tails] from freezing/solidifying; Teacher’s comments:  Please take note of the edit in the question. Due to the errata, marks were still awarded if students wrote fatty acids instead of fatty acid tails. However, note that fatty acids are different from fa tty acid tails. Fatty acids are long -chained carboxylic acids, consisting of a long hydrocarbon chain and a carboxyl group. Fatty acid tails are fatty acids that have formed ester bonds with glycerol in phospholipids (or triglycerides).  Fats were rejected as fats are esters of fatty acids but the specific type of lipids in cell membranes is phospholipids.  Quite a large number of students mentioned the presence