NYGH 2014-S3EOY-Bio P1 & P2 Ans

2014 SEC 3 BIO IP EOY ANSWERS 1a The marble : nucleus; The beads : chloroplasts; (accept: mitochondrion) The tubing : cell/plasma membrane; [3] 1b Vacuole; ribosomes; starch grains; mitochondria; tonoplast; endoplasmic reticulum; Golgi apparatus (any 2) [2] 1c water leaves;
 by osmosis;
 ref. water potential (any ref. to differential in concentration / less negative water potential to more negative water potential);
 cell / cytoplasm / protoplasm / model shrinks;
 ref. decreased pressure / turgidity / firmness / flaccidity;
 tubing pulls away from permeable membrane OR cytoplasm or cell membrane pulls away from (cell) wall;
 ref. plasmolysis;
 no sugar leaves cell / enters space between tubing and permeable membrane OR between cell membrane and wall; (any 4) [4] 1d Compare: Osmosis will still observed in the plant cell as compared to model plant cell; Contrast: The plant cell wall will still maintain its original shape because plan t cell wall is rigid/firm unlike the flexible permeable membrane of the model cell which will also shrink together with inner tubing; (max 2 marks) [2] 2a As temperature of the environment is increased from 2 to 45 oC, kinetic energy increases and enzyme and substrate molecules move faster; Resulting in more successful collisions per unit time and E-S complex is formed at a higher rate until the rate of formation of E -S complex is at its maximum at optimum temperature; At temperatures beyond 45oC (optimal temp), thermal agitation of enzyme disrupts the weaker bonds and distorts th e specific three -dimensional conformation of enzyme/ bonds holding enzyme in 3D form are broken; Active site is distorted and no longer complementary to substrate and enzyme is said to be denatured; [3] 2b Enzymes would be exposed to a higher temperature for a longer period of time; [1] 2c At low substrate concentration, increase in substrate concentration increases the number of successful collisions between enzyme and substrate molecules; Thus, there is increase in number of enzyme -substrate complex being formed, hence proportional increase in rate of formation of products; Not all active sites of the enzymes are occupied, but at high substrate concentration, all active sites of enzymes are occupied and enzyme concentration becomes limiting; Max 2 marks [2] 2d Increase enzyme concentration / increase temperature; A: Adjust pH to optimum pH R: Change temperature, High temperature, warmer environment, high enzyme concentration (two words answer) [1]

2014 End-of-Year Examination Secondary Three 2 Nanyang Girls’ High School Setters: MS, JL, OC Biology /II 3a L Outer: brown Inner: blue-black M Outer: brown Inner: brown N Outer: brown Inner: brown [1] 3b (L) photosynthesis/carbohydrate (or named) production; uses up carbon dioxide; (M) Carbon dioxide released via respiration by the plant; Absorbed (by substance); (N) respiration/no photosynthesis; Carbon dioxide released; [6] 4a Carbohydrate metabolism – description of storage of glycogen ; Fat metabolism – production of bile will be affected; Storage of iron from broken down red blood cells ; Metabolism of amino acids and formation of urea ; Breakdown of alcohol or other harmful substances into harmless substances ; (Any reference to the above functions ) ; [4] 4b Excessive intake of either fatty food/high carbohydrate food ; Excessive & prolonged intake of alcohol; [1] 5a Semilunar/aortic valve opens; [1] 5bi [1] 5bii Bicuspid valve prevents backflow of blood / faulty valve cannot prevent backflow; From ventricle to atrium; Overall less volume of blood in ventricle / ventricle cannot fill to max, thus lower pressure; [2] 6a 1 – correctly labeled body part ON diagram; 1 – correctly named chemical related to body part; 1 – correctly described effect must be linked to chemical; (eg. tar paralyses cilia in trachea) [3] 0.2 0.4 0.6 0.8 time/s pressure/mm mercury ventricle aorta atrium B 1.0 1.2 1.4 Ventricular graph has lower max pressure;

2014 End- of-Year Examination Secondary Three 3 Nanyang Girls’ High School Setters: MG, JL, OC Biology /II [Turn over 6b, c Expose human to specific chemical and see if they develop the disease; Expose animal to specific chemical and see if they develop the disease; Apply chemical to cultured lung cells in petri dish and see if disease develops; [1] 6c 1 – for correct assessment of how ethical experiment is 1 – for reason given [2] 7a G sieve tube (element) AND H companion cell; [1] 7b The vessels have thicker walls;
 thickening in walls (e.g. spiral, annular, reticulate); wider lumen;
 no cytoplasm; R dead (not structure)
 pits;
 no cross walls / no sieve plates / no sieve pores; lignin; [3] 7c (sucrose) loaded into sieve elements/tubes at source/leaf by active transport with the help of companion cells;
 water potential in sieve elements/tubes become more negative; absorption of water / water enters by osmosis from xylem vessels;
 hydrostatic pressure builds up/mass flow;
 (sucrose) unloaded at sink / fruit to give a difference in pressure (between source and sink); [4] 7d sucrose used in respiration;
 stored as starch;
 used to make, cellulose / used to make cell walls
 stored as / converted to, organic acids (in vacuoles); converted into named other substances; e.g. lipid / protein [2] 8a Large molecule which is insoluble in water and thus does not change the water potential of the cell; Large molecule and thus not able to diffuse out through the cell membrane; Highly branched and contain many glucose molecules able to be hydrolysed and used during respiration; Compact shape and thus occupy lesser space compared to individual glucose units; Examiner’s comments: Candidates used “it” frequently and did not specify what does “it” refer to. Some candidates wrote long sentences with wrong concepts in them causing them to lose marks for correct points. [3] 8b Wall has numerous folds which increases sur face area to volume ratio for absorption; Wall is line with numerous minute finger-like projections called villi; Epithelial cells of the villi have numerous finger-like projections known as micro - villi; Small intestine is long and enable longer period of absorption; Villi has one cell thick epithelium ensuring short diffusion distance to increase rate of absorption; Intestinal wall and villi are well supplied with blood and lymphatic capillaries to carry away the absorbed food substances; [5]

2014 End-of-Year Examination Secondary Three 4 Nanyang Girls’ High School Setters: MS, JL, OC Biology /II 8c Digestion only reaches completion in the small intestine , where the necessary enzymes are available to break down fats, proteins and carbohydrates into their smallest sub-units; Only when the food substances are at their simplest form will they be able to be absorbed efficiently; [2] 9Ea Pulmonary artery (PA) contains less oxygen than Hepatic artery (HA); PA contains more carbon dioxide than HA; PA contains more glucose than HA; PA pressure is lower than HA; PA contains more urea than HA; (any 2) [2] 9Eb FAINTING Due to low red blood cell count of 2.9 X 1012 cells per litre ; As less oxygen is transported during hike/ bound to haemoglobin for transport; (Brain) receives less oxygen for respiration (leading to fainting); [8] PROLONGED BLEEDING Due to low platelet count of 77 X 109 cells per litre; Less platelets to produce thrombokinase, which converts prothrombin to thrombin; In presence of calcium ions; Thus less thrombin converts fibrinogen to fibrin; Thus cannot form fibrin mesh which traps blood components to form a clot (as quickly as normal person); INFECTION Due to s