2024 ACJC H2 Bio P2 MS

This document consists of __ printed pages. [Turn over Anglo-Chinese Junior College JC2 Biology Preliminary Examination Higher 2 CANDIDATE NAME FORM CLASS TUTORIAL CLASS I N D E X NUMBER BIOLOGY Paper 2 Structured Questions Candidates answer on the Question Paper. No Additional Materials are required. 9744/02 22 August 2024 2 hours READ THESE INSTRUCTIONS FIRST Write your Name, Class and Index 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 staples, paper clips, glue or correction fluid. Answer all questions in the spaces provided on the Question Paper. 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. For Examiners’ use only 1 / 8 2 / 10 3 / 11 4 / 10 5 / 11 6 / 9 7 / 10 8 / 10 9 / 10 10 / 5 11 / 6 Total / 100

2 Anglo-Chinese Junior College 2024 J2 H2 9744 Paper 2 Preliminary Examination For Examiner Use Answer all questions. 1 Fig. 1.1 is an electron micrograph of a cell found in the human adrenal cortex which secretes the hormone adrenaline into the bloodstream. Fig. 1.1 (a) (i) Identify organelle P. Mitochondrion; R! mitochondria …………………………………………………………………………………………………. [1] (ii) Describe how organelle P is involved in the secretory process of the cell in Fig. 1.1. 1. ATP is synthesised during aerobic respiration/ Krebs cycle/ oxidative phosphorylation/ chemiosmosis; R! cellular respiration, glycolysis …………………………………………………………………………………………………….. 2. To provide energy R! produce energy for the synthesis and secretion of the secretory products via exocytosis; …………………………………………………………………………………………………. [2]

3 [Turn over Anglo-Chinese Junior College 2024 J2 H2 9744 Paper 2 Preliminary Examination For Examiner Use (b) Cells expressing proteins of interest are allowed to take up radioactively labeled amino acids for a brief interval, during which all newly synthesised protei ns will exhibit a certain level of radioactivity. Fig. 1.2. shows the percentage of radioactivity found in three organelles of the endomembrane system, X, Y and Z within the span of two hours. Fig. 1.2 ( i ) Identify organelle Y. Rough endoplasmic reticulum; R! rough ER / RER , ribosomes …………………………………………………………………………………………………. [1] (ii) Using Fig. 1.2, account for the level of radioactivity in organelle Y. 1. *Radioactivity from 100% at 1.5 minutes (A! 2 minutes) decre ased sharply to 55% (A! 50-60%) at 3 minutes OR 10% (A! 8-11%) at 120 minutes; …………………………………………………………………………………………………….. 2. Initially high due to synthesis of polypeptides by ribosomes attached to outer membrane of rough ER and entering the rough ER lumen. …………………………………………………………………………………………………….. 3. decreases as proteins / polypetides synthesised are being pa ckaged into transport vesicles which bud off from the rough ER; …………………………………………………………………………………………………….. @ 1 mark, max 2 *MP1 compulsory …………………………………………………………………………………………………. [2] (b)(iii)

4 Anglo-Chinese Junior College 2024 J2 H2 9744 Paper 2 Preliminary Examination For Examiner Use (iii) Bafilomycin A1 is a chemical inhi bitor that blocks the process of exocytosis at the cell surface membrane. This causes a change in one of the graphs in Fig 1.2. On Fig. 1.2, sketch a graph that represents this expected change. [1] Higher radioactivity in organelle X R! increase in graph before 15 minutes ( i v ) Explain your answer in (b)(iii). Secretory vesicles are unable to fuse with the cell surface mem brane, hence the secretory product / protein will remain in them / remain in the cell; ………………………………………………………………………………………….............[1] [Total: 8]

5 [Turn over Anglo-Chinese Junior College 2024 J2 H2 9744 Paper 2 Preliminary Examination For Examiner Use 2 Collagen plays a structural role and contributes to mechanical properties and shape of tissues in the body. Fig. 2.1 shows the approximate co mposition of collagen and the molecular structure of four of the amino acids found in it. Fig. 2.1 (a) (i) With reference to Fig. 2.1, explain why collagen is an insoluble protein. 1. Alanine, proline and glycine make up 10, 12 (A! 11.5) and 33 % (A! 32%) of amino acids in collagen respecti vely / 55% (A! 54%) of the amin o acids in collagen; …………………………………………………………………………………………………….. 2. which makes up the majority / m ore than half of amino acids in collagen; …………………………………………………………………………………………………….. 3. All three amino acids (alanine, proline and glycine) have no n-polar/ hydrophobic R groups, will not be able to form hydrogen bonds with water molecules; R! hydroxyproline …………………………………………………………………………………………………….. 4. Hydroxyproline is a polar amino acid but the OH group is use d to form H bond with other polar residues in adjacent α-chains of tropocol lagen, hence not be able to form hydrogen bonds with water molecules;; …………………………………………………………………………………………………….. @ 1 mark, max 3 …………………………………………………………………………………………………. [3] composition in collagen / % amino acids

6 Anglo-Chinese Junior College 2024 J2 H2 9744 Paper 2 Preliminary Examination For Examiner Use (ii) Explain why the abundance of glycine in collagen is essential for its function. 1. Glycine has a small R-group of all amino acids (-H only) for ming collagen; …………………………………………………………………………………………………….. 2. This allows the α-chains of tropocollagen to be able to wind tightly together/ fit into the restricted space between α-chains to allow formati on of hydrogen bonds/ cross-links; R! α-helix …………………………………………………………………………………………………….. 3. Which leads to an increase in tensile strength of collagen, making it a suitable structural protein; …………………………………………………………………………………………………. [3] (b) Fig. 2.2 shows how changes in concentration of oxygen affects its binding to haemoglobin. Fig. 2.2 ( i ) State the property of haemoglobin that is illustrated in Fig. 2.2. Cooperativity; …………………………………………………………………………………………………. [1] oxygen binding to haemoglobin / % oxygen concentration / mm Hg

7 [Turn over Anglo-Chinese Junior College 2024 J2 H2 9744 Paper 2 Preliminary Examination For Examiner Use (ii) Using your knowledge of the struct ure of haemoglobin, explain h ow the property stated in (b)(i) enhances its function. 1. Haemoglobin is made up of 4 polypeptides/ two dimers each ca rrying a haem group; …………………………………………………………………………………………………… 2. the two dimers are held together by weak hydrogen bonds, res ulting in the ability of the two dimers to move with respect to each other; …………………………………………………………………………………………………… 3. the binding of an oxygen molecule to one subunit induces a conformational change in the re maining subunits, which increase s the affinity for oxygen in these subunits; …………………………………………………………………………………………………… 4. *This facilitates the effecti ve loading and unloading of oxygen at the lungs and body tissues respectively; *MP4 comp