CCHY 2018 Bio Yearly TYS ANS

6093 Biology Yearly TYS 2018 No Paper 1 Marks Remarks 1 C 1 2 A 1 3 B 1 4 B 1 5 C 1 6 D 1 7 C 1 8 A 1 9 B 1 10 A 1 11 C 1 12 B 1 13 C 1 14 D 1 15 A 1 16 B 1 17 C 1 18 C 1 19 B 1 20 D 1 21 B 1 22 D 1 23 A 1 24 D 1 25 C 1 26 C 1 27 D 1 28 B 1 29 B 1 30 A 1 31 C 1 32 D 1 33 A 1 34 C 1 35 D 1 36 A 1 37 C 1 38 B 1 39 D 1 40 D 1 Total 40

Paper 2 Section A Marks Remarks 1ai chromatid 1 1aii stage 3: metaphase stage 4: anaphase 1 1 1bi 2 1 1bii plant 1: AA plant 3: aa 1 Total 5 2ai regulation of blood glucose concentration/ deamination of excess amino acids into ammonia and then urea/ breakdown of haemoglobin and stores iron released/ detoxification of alcohol by alcohol dehydrogenase into acetaldehyde/ production of bile used for emulsification of fats 3 2aii C 1 2aiii name: bile; function: emulsify fats into smaller fat droplets to increase surface area to volume ratio for faster digestion of fats by lipase; 1 1 2bi 40 °C 1 2bii rennin has denatured at high temperatures of 60 °C beyond optimum temperature + active site is altered + substrate is unable to bind to enzyme to form e nzyme- substrate complex; 1 2c solid lumps remains in the stomach longer compared to liquid milk; allows complete digestion and greater absorption of nutrients; 1 1 Total 10

3ai 3 minute 1 3aii as temperature increases from 15 °C to 21 °C, clotting time decreases rapidly from 24 min (longest time taken) to 10 min; as temperature increases further to 35 °C, clotting time continue to decreases gradually to 2.5 min + lowest time taken for clotting/ as temperature increases from 15 °C to 35 °C, clotting time decreases from 24 min to 2.5 min; rate of clotting increases when temperature increases; 1 1 R: no quotation of data 3b prevents foreign particles from entering the bloodstream; prevent excessive loss of blood; 1 1 Total 5

4a S: walls of alveoli are richly supplied with blood capillaries + F: continuous flow of blood maintains a steep concentration gradient for faster diffusion of gases; S: thin film of moisture covers the inner surface of the alveolus + F: dissolve gases for faster diffusion; S: walls of alveoli are one-cell thick + F: provides short diffusion distance for faster diffusion of gases; S: numerous alveoli in the lungs + F: provide large surface area to volume ratio to increase rate of diffusion of gases; 3 structure + function 4b lower levels of carbonic anhydrase to catalyse the reaction between carbon dioxide and water in RBCs + forming lower amounts of carbonic acid; decrease amount of carbon dioxide converted to hydrogencarbonate ions for transport in the blood plasma; lower rate of carbon dioxide being transported to the lungs for excretion + leads to carbon dioxide poisoning/ excess carbon dioxide in the RBC/ slower gaseou