2022 SASS Bio 4E MYE Ans

Mid-Year Examination 2022/4Exp/Biology/Ans Paper 1 – MCQ 1 A 11 D 21 A 31 C 2 B 12 D 22 A 32 B 3 A 13 C 23 A 33 B 4 C 14 D 24 B 34 C 5 A 15 A 25 C 35 C 6 C 16 D 26 C 36 D 7 B 17 C 27 B 37 C 8 C 18 A 28 D 38 D 9 B 19 D 29 D 39 C 10 D 20 C 30 C 40 D Paper 2 – Section A (50 marks) Answer Marks Marker’s Report 1a A - digestion B - absorption C - deamination D - excretion Any 2 correct for 1 mark 2 1b Trypsin Peptidase 1 1 R: pepsin (Qn states small intestine) 1c - Amino acids are absorbed from the lumen of the small intestine into the blood capillaries of the villi - Through diffusion and/or active transport depending on difference in concentration gradient between small intestine and blood capillaries 1 1 Some did not specify villi / missed out on active transport. 1di 1 R: respiration (too vague) 1dii glucose + oxygen  carbon dioxide + water + energy 1 R: carbohydrate Some left out energy. aerobic respiration 1

Mid-Year Examination 2022/4Exp/Biology/Ans 1e - water potential of blood plasma increases / water potential of blood plasma is higher than blood cells - causing water molecules to move from blood plasma into blood cells - by osmosis - blood cells will swell / burst Any 2 for 1 mark 2 R: water Some left out name of process. 2a 5000 – 1500 = 3500 cm3 1 R: no units 2b - diaphragm relaxes and arches upwards - external intercostal muscles relax, - internal intercostal muscles contract - ribs move downwards and inwards - thoracic volume decreases - atmospheric pressure now lower than pressure in lungs - air is forced out of lungs Any 2 for 1 mark 3 R: pressure decreases (must show comparison) 2c Both increase in frequency + increase in volume must be observed 1 Drawings between V and W would not be marked. Poorly done. Most students indicated an increase in volume but not frequency. 2d Spirogram of person suffering from chronic bronchitis would indicate a increase in speed / decrease in volume of air inspired and expired by the lungs. 1 A: smaller wavelength / amplitude 3a - Down’s syndrome - It is a disease caused by an extra copy of chromosome 21 present. 1 1 Accept any other valid ans 3bi From prophase I to anaphase I 1 R: prophase to anaphase 3bii - During prophase I, the newly replicated chromatin threads condense to form chromosomes - During anaphase I, homologous chromosomes are separated to opposite poles of the cell 1 1 Some simply repeated information in the question 2

Mid-Year Examination 2022/4Exp/Biology/Ans text rather than substantiating with the processes that specifically happens in those stages. 4ai - Suggest: Increase in adrenaline - Explain: Stimulate conversion of glycogen to glucose OR - Suggest: After a meal high in sugar / starch / carbohydrates / glucose - Explain: Glucose is absorbed / diffused into the bloodstream by the small intestine 2 Some students showed no / weak understanding of the concept of homeostasis. 4aii - Suggest: blood glucose concentration falls