MI 2023 J2 H2 BI Prelim P2 QP

Class Adm No Candidate Name: ___________________________________ This question paper consists of 28 printed pages, including 2 blank pages. [Turn over] 2023 End-of-Year Examination Pre-University 3 H2 Biology 9744/02 Paper 2 Structured Questions 12 September 2023 2 hours READ THESE INSTRUCTIONS FIRST Do not open this booklet until you are told to do so. Write your Admission number and name on all the work you hand in. Write in dark blue or black pen on both sides of the paper. You may use a soft pencil for any diagrams, graphs or rough working. Do not use staples, paper clips, highlighters, glue or correction fluid. Answer all questions in the question booklet. At the end of the examination, fasten all your work securely together. The number of marks is given in brackets [ ] at the end of each question or part question. At the end of the examination, fasten all your work securely together. For Examiner's Use 1 /10 2 /9 3 /10 4 /12 5 /10 6 /13 7 /11 8 /12 9 /5 10 /8 Total /100

2 9744/02/PU3 EOY/2023 Answer all questions. 1. Biomolecules function as building blocks for macromolecules to be assembled. Carbohydrate is made up of many monosaccharides and can be found in both animals and plants. (a) Name the bond formed between monomers in cellulose. ……………………………………………………………………………………………… [1] (b) Illustrate with a labelled diagram how two monomers form the bond in (a) in cellulose. Circle the bond formed between the two monomers. Fig. 1.1 shows the partial structure of the monomer. Fig. 1.1 [4]

3 9744/02/PU3 EOY/2023 [Turn Over] (c) One of the defining features of all cells is the cell surface membrane. This membrane is composed of phospholipid bilayer, with other biomolecules dispersed throughout the bilayer. (i) Describe the roles of carbohydrates in the cell surface membrane. ……………………………………………………………………………………………… ……………………………………………………………………………………………… ……………………………………………………………………………………………… ………………………………………………………………………………………….. [2] (ii) During the synthesis of phospholipid, the phospholipid sometimes needs to be moved between the layers. The movement is facilitated by a transmembrane protein called floppase. Fig.1.2 shows floppase moving a phospholipid from the inner layer to the outer layer of the cell surface membrane. Fig. 1.2 Due to their hydrophilic heads, phospholipid molecules cannot cross the hydrophobic region of the membrane from the inner layer to the outer layer without floppase. Using your knowledge of proteins, suggest how the structure of floppase allows phospholipids to cross the hydrophobic region of the membrane. ……………………………………………………………………………………………… ……………………………………………………………………………………………… ……………………………………………………………………………………………… ……………………………………………………………………………………………… ……………………………………………………………………………………………… ………………………………………………………………………………………… [3] [Total :10]

4 9744/02/PU3 EOY/2023 2. Catalase is an enzyme that catalyses the decomposition of hydrogen peroxide, which is a toxic product of metabolism. A scientist investigated the activity of two forms of catalase, P and Q, extracted from Anopheles gambiae, an important vector of malaria. The scientists investigated the effect of increasing concentration of hydrogen peroxide on the activity of these two forms of catalase. The results are shown in Fig. 2.1. Fig. 2.1 (a) With reference to Fig. 2.1, describe and explain the effect of increasing concentration of hydrogen peroxide on the activity of catalase P. …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... ……………………………………………………………………………………………… [4]

5 9744/02/PU3 EOY/2023 [Turn Over] (b) Each molecule of catalase consists of four identical polypeptides. The two forms of catalase in Anopheles gambiae differ by only one amino acid at position 2 in the amino acid sequence. Explain how the difference in one amino acid sequence is responsible for the lower activity of catalase Q compared with catalase P. …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... ……………………………………………………………………………………………… [3] (c) Female mosquitoes feed on blood in order to produce their eggs. After feeding, the metabolic rate increases for egg production. The scientist allowed female mosquitoes to feed on blood. They found that female mosquitoes with only catalase P produced more eggs than those with only catalase Q. Suggest why there is a difference in egg production between the two types of Anopheles gambiae. …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... ……………………………………………………………………………………………… [2] [Total :9]

6 9744/02/PU3 EOY/2023 3. (a) State the function of DNA and describe its property that allow it to perform this function. …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... ……………………………………………………………………………………………… [2] (b) In a somatic cell of a eukaryote, 20% of the nitrogenous base in the nuclear DNA is thymine. Calculate the percentage of nitrogenous base in the nuclear DNA of this cell that is guanine and explain your answers. Show your working clearly in the space below. …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... ……………………………………………………………………………………………… [3]

7 9744/02/PU3 EOY/2023 [Turn Over] (c) Fig. 3.1 shows the process of DNA replication. Fig. 3.1 (i) In the boxes provided in Fig. 3.1, label the end of DNA with either • 3’ or • 5’. [1] (ii) Explain why DNA is replicated differently in Box A and Box B. ……………………………………………………………………………………………… ……………………………………………………………………………………………… ……………………………………………………………………………………………… ………………………………………………………………………………………… [2] (d) During protein synthesis, DNA is used as a template to form mRNA and the resulting mRNA is used as a template to form polypeptide chain. Describe 2 other differences between the enzyme used to form mRNA and the enzyme used to form polypeptide chain. …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... ……………………………………………………………………………………………… [2] [Total :10]

8 9744/02/PU3 EOY/2023 4. Sickle cell anaemia is most commonly caused by the haemoglobin variant HbS , a result of a point mutation. (a) Describe the effect of the point mutation to haemoglobin. …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... …………………………………………………………………………………………………... ……………………………………………………………………………………………… [4] (b) Sickle cell anaemia can be treated with a drug called hydroxyurea which induces the formation of fetal haemoglobin (HbF). HbF is normally found in fetus and newborn. When pres ent in individuals with sickle cell anaemia, HbF prevents sickling of red blood cells. (i) Suggest how formation of HbF would be induced. ……………………………………………………………………………………………… ……………………………………………………………………………………………… ……………………………………………………………………………………………… ………………………………………………………………………………………… [2] (ii) Suggest how elevated levels of HbF may reduce the sympto