SJI 2020 Y3 EOY Biology 6093 student answers

St Joseph’s Institution END-OF-YEAR Examination 2020 Year 3 Biology OP Page 1 of 12 Marking Scheme SUBJECT: BIOLOGY EXAMINATION: END-OF-YEAR LEVEL: YEAR 3 OP Paper 1 Paper 2 Section A: QN NO. SUGGESTED ANSWER SCHEME (PAPER 2 SECTION A) 1ai) Gland cell ii) To secrete mucus to trap dust particles and micro-organisms. bi) Increase in volume will lead to decrease in pressure of thoracic cavity. Inversely proportional ii) Internal intercostal muscle contracts, external intercostal muscle relaxes; Ribcage and sternum moves downwards and inwards; Diaphragm relaxes and arches upwards; This leads to decrease in thoracic cavity volume and increase in pressure of thoracic cavity; Pressure in the thoracic cavity is higher than the surrounding and air leaves the lungs; c) Carbon monoxide binds permanently with haemoglobin to from carboxyl haemoglobin; 1 C 9 A 17 C 25 A 2 B 10 D 18 C 26 B 3 B 11 D 19 A 27 D 4 A 12 C 20 D 28 A 5 B 13 A 21 C 29 A 6 D 14 B 22 D 30 D 7 C 15 A 23 A 8 A 16 D 24 A

St Joseph’s Institution END-OF-YEAR Examination 2020 Year 3 Biology OP Page 2 of 12 QN NO. SUGGESTED ANSWER SCHEME (PAPER 2 SECTION A) This results in lesser oxygen being transported in the body; Lower rate of aerobic respiration, less energy released+ person will feel fatigued; Increase fatty deposits on the arteries; Lesser oxygen supplied to heart muscles+ lower rate of aerobic respiration+ higher chance of coronary heart disease 2a 0.3s 0.1-0.4s b) During ventricular systole, ventricle walls contract. Pressure in the ventricles is higher than the atria+ This increase in pressure in the ventricles causes the bicuspid and tricuspid valves to close to prevent backflow of blood into the atria. This produces a ‘lub’ sound. During ventricular diastole, the ventricle walls relax. Pressure in the ventricles is lower than the atria+ The lowered pressure in the ventricles causes the semilunar valves to close. This produces a ‘dub’ sound. ci) 138-64/64X100%=116% ii) Increase in heartbeat+ Increase in breathing rate; (no explanation) Increase in muscular contractions during the exercise + requires large amount of energy Increase rate of aerobic respiration to meet the increase in energy demand; Increase in heartbeat to supply blood containing oxygen and glucose at a faster rate +to muscle tissues; Increase in breathing rate to supply oxygen for aerobic respiration and to remove carbon dioxide produced; iii) Produced during anaerobic respiration in muscle cells, when insufficient oxygen is available for aerobic respiration. Accumulation of lactic acid in muscles may cause fatigue, muscular pains and cramps.

St Joseph’s Institution END-OF-YEAR Examination 2020 Year 3 Biology OP Page 3 of 12 QN NO. SUGGESTED ANSWER SCHEME (PAPER 2 SECTION A) 3a capillary, Any two from: blood cells move in Vessel B in single file AW / running between body cells / walls are one-cell thick (not a valid answer as not shown in fig. 3.1 at all, only accepted for current exam) / substances diffuse / move out of vessel B at C / part of a network of vessels, 3b Either: discussion on formation of tissue fluid High hydrostatic pressure in the blood capillaries; Forces small molecules (water molecules / glucose / amino acids ) out of the blood capillaries into the tissue fluid ; Or: discussion on diffusion of molecules / ions OUT of blood capillary at C Diffusion of molecules such as glucose / amino acids / oxygen ; from blood plasma into the tissue fluid ; 3ci B – phagocyte C – lymphocyte ; 3cii problem:

St Joseph’s Institution END-OF-YEAR Examination 2020 Year 3 Biology OP Page 4 of 12 QN NO. SUGGESTED ANSWER SCHEME (PAPER 2 SECTION A) reduced immunity / immune response / less able to fight infection / kill microorganisms or pathogens / more likely to suffer (infectious) disease* ; explanation: refer to how less phagocytosis by phagocytes will occur ; refer to how less antibody production by lymphocytes will occur; refer to function of antibody and how the lacking of antibody will affect the killing / destruction of microorganisms / pathogens/bacteria/viruses ; remain in blood / body / not destroyed, leading to infection / infectious disease * ; * should only be awarded once in this entire question 4a Final mass is higher than initial mass ; Sucrose solution has lower water potential compared to distilled water ; Net movement of water molecules from the distilled water into the sucrose solution, across the partially-permeable membrane, via osmosis ; 4bi Similarity: both has partially-permeable membrane; Differences: Epithelial cells has microvilli, while Visking tubing do not ; 4bii Sucrose molecules are large molecules and therefore unable to move across the partially-permeable membrane of the Visking tubing ; 4biii Digestion is the break down of large, complex food molecules into smaller, simpler and diffusible ones; Only small molecules can diffuse through the partially-permeable cell membrane of the epithelial cells in the villi, allowing for absorption to take place ;

St Joseph’s Institution END-OF-YEAR Examination 2020 Year 3 Biology OP Page 5 of 12 QN NO. SUGGESTED ANSWER SCHEME (PAPER 2 SECTION A) 4c When in high concentrations, starch molecules are large molecules that cannot diffuse out of the cell due to the partially - permeable membrane, unlike glucose, allows for storage of glucose molecules in a cell; Structure of starch molecules are more compact compared to individual molecules of glucose, allowing for more space to store more glucose molecules; Accept: Starch molecules do not dissolve in water, unlike glucose, thus will not change the water potential of the cell sap; 5a) Carbon dioxide + water  glucose + oxygen Conditions: chlorophyll + light energy b) Type of plant; light intensity c) carbon dioxide uptake of J is higher (at all temperatures except at 10 °C) ; peak / optimum / maximum / best, uptake of J is at a higher temperature+ quote data from x/y axis correct use of comparative data between J and H, quote data from both x/y axis values with correct units di) temperature is a limiting factor ; photosynthesis is an enzyme catalysed reaction; increases, kinetic energy / the movement of molecules / diffusion ; more collisions between substrate and enzymes to form enzyme-substrate complexes ; ii) enzymes are denatured ; loss of active site + no enzyme-substrate complex formed;

St Joseph’s Institution END-OF-YEAR Examination 2020 Year 3 Biology OP Page 6 of 12 QN NO. SUGGESTED ANSWER SCHEME (PAPER 2 SECTION A) 6a MP1 Concentration of glucose in Q is higher than P; MP2 (in liver) Glucose molecules diffuse from blood capillaries into the liver cells and is used for aerobic respiration; MP3 Liver cells converts excess glucose in to glycogen for storage ; 6b MP1 Liver cells secrete bile which emulsifies fats (in which large fat globules becomes smaller oil droplets) ; MP2 Increases surface area-to-volume ratio of the globules, increases rate of digestion of fats by lipase MP3 Without bile, rate of fats digestion by lipase decreases in the small intestine + not absorbed and end up in large intestine + egested as part of faeces MP4 Deamination of excess amino acids occurs in the liver cells MP5 Without this process, no urea is formed and transported to the kidneys, where urine formation occurs; MP6 Liver cells contain alcohol dehydrogenase that detoxify / breaks down alcohol into harmless molecules / glucose / acetyaldehyde ; MP7 Without which, alcohol is transported to the brain, which results in dizziness/ slower reflexes 7a MP1 water molecules evaporates from the thin film of moisture on the spongy mesophyll to form water vapour; MP2 Accumulation and increase of concentration of water vapour molecules in the intercellular