2016 VJC H2 Biology Prelims Paper 2 Questions

VICTORIA JUNIOR COLLEGE BIOLOGY DEPARTMENT JC2 PRELIMINARY EXAMINATIONS 2016 Higher 2 VICTORIA JUNIOR COLLEGE VICTORIA JUNIOR COLLEGE VICTORIA JUNIOR COLLEGE VICTORIA JUNIOR COLLEGE VICTORIA JUNIOR COLLEGE VICTORIA JUNIOR COLLEGE VICTORIA JUNIOR COLLEGE VICTORIA JUNIOR COLLEGE VICTORIA JUNIOR COLLEGE VICTORIA JUNIOR COLLEGE VICTORIA JUNIOR COLLEGE VICTORIA JUNIOR COLLEGE VICTORIA JUNIOR COLLEGE VICTORIA JUNIOR COLLEGE VICTORIA JUNIOR COLLEGE VICTORIA JUNIOR COLLEGE VICTORIA JUNIOR COLLEGE VICTORIA JUNIOR COLLEGE VICTORIA JUNIOR COLLEGE VICTORIA JUNIOR COLLEGE CANDIDATE NAME CLASS 1 5 S EXAM NUMBER BIOLOGY 9648/02 Paper 2 Core Paper 14 September 2016 Additional Materials: Answer Paper 2 hours READ THESE INSTRUCTIONS FIRST Write your Class, exam number and name on all the work you hand in. Write in dark blue or blue pen. You may use a soft pencil for any diagrams or graphs. Do not use any staples, 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 on the writing paper provided. 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 the appropriate units. At the end of the examination, 1. hand in sections A and B separately; 2. fasten all your work securely; 3. enter the question number of section B that you have answered in the grid opposite. The number of marks is given in brackets [ ] at the end of each question or part question. This paper consists of 20 printed pages. For Examiner’s Use Section A 1 2 3 4 5 6 7 8 Section B Total

1    Section A: Structured questions Answer all the questions. All answers must be written on the spaces provided and nowhere else. 1 (a) Fig. 1.1 shows the electro-micrograph of a T-helper cell found in the bloodstream of a healthy individual. Fig 1.2 shows the how a region of the T- helper cell looks like when magnified. Fig. 1.1 EM of T helper cell Fig. 1.2 Magnified region of a part of the T helper cell (i) Identify structures P and Q and describe briefly their functions. [3]

2    (ii) Contrast the structure of a lysosome with structure P. [2] (b) The cytoplasm of T-helper cells contains different proteins and enzymes, one of which is phosphofructokinase involved in the metabolism of glucose to produce energy necessary for cell survival and func tions. In order to ensure a constant supply of energy, most organisms have evol ved the use of storage molecules to store excess glucose. (i) Name a carbohydrate that functions as a storage molecule for T-helper cells. [1] (ii) Describe three structural differences between the carbohydrate named in (b) (i). and cellulose. [3] (iii) Explain how the presence of two types of bonds in amylopectin enables it to carry out its function. [3]

3    (c) Phosphofructokinase is an allosteric en zyme. Explain how the presence of an allosteric inhibitor affects the enzymatic activity of an allosteric enzyme. [2] [Total: 14]

4    2 The Fig. 2.1 shows an enzyme involved in t he activation of tRNA for translation in prokaryotes. Fig 2.1 (a) (i) Explain the mode of action of this enzyme. [3] (ii) Explain the significance of having more than one type of the enzyme named in (a) (i) in the cell. [2]

5    (b) How does the order of nucleotides in a gene encode the information that specifies the primary stru cture of a polypeptide? Incl ude two features of the genetic code in your answer. [3] (c) Explain how different polypeptides c an be synthesised simultaneously from a single mRNA is produced from an operon in prokaryotes. [2]   [Total: 10]

6    3 Fig. 3.1 shows the arg operon found in Escherichia coli. In the absence of arginine, the operon is in the active state. In the presence of arginine, the expression of the structural genes decreases. Fig 3.1 (a) Using Fig 3.1 explain the mode of control of the Arg operon. [2] (b) Explain why it is useful for a bacteri al cell to decrease expression of the structural genes when arginine is present. [2]

7    Besides having operons, bacteria c an have other means to enhance their adaptability to the changing environment thr ough gene transfer. Fig. 3.2 shows one way in which bacteria can acquire new genetic material. Fig. 3.2 (c) Name and describe the process which can result in this population of bacteria acquiring the same allele needed to increase their likelihood of survival. [3]

8    Fig. 3.3 shows a classic ex periment used to show that physical contact between bacterial cell is necessary in order for conjugation to happen Fig. 3.3 (d) A student tried to replicate the experiment but did not get the result shown in Fig. 3.3. Instead, he observed a few bacterial colonies which are hybrids of strains A and B. He later realized that he had accide ntally forgot to add in DNAase when carrying out the experiment. (i) Briefly describe the role of DNAase in this experiment [1] (ii) How does the lack of DNAase in the exper iment result in the growth of the hybrid bacterial colonies? [2] [Total: 10]

9    4 The majority of lung cancers are caus ed by long term exposure to the several classes of carcinogens present in tobacco smoke. However there are instances of lung cancers arising in the absence of det ectable tobacco exposure. Analysis of the different mutations in individuals who smoked (ever-smokers) and those who did not (never-smokers) suggest that lung cancer s in never smokers may follow a very different cellular and molecular pathway of malignant transformation. The Fig. 4.1 shows the differential frequencies of gene mutations of the epidermal growth factor receptor ( EGFR) and Ras reported in l ung adenocarcinomas in Asia versus United States, in never-smokers and ever-smokers. http://clincancerres.aacrjournals.org/content/15/18/5646 Fig. 4.1 With reference to Fig. 4.1, (a) (i) describe the effect of Ras and EGFR mutations on the development of lung cancer in never-smokers and ever –smokers in Asia. [1]