CCHY 2021 Bio Yearly TYS ANS

6093 Biology Yearly TYS 2021 No Paper 1 Marks Remarks 1 C 1 2 B 1 3 D 1 4 D 1 5 A 1 6 D 1 7 C 1 8 C 1 9 B 1 10 A 1 11 B 1 12 A 1 13 B 1 14 B 1 15 A 1 16 D 1 17 C 1 18 A 1 19 C 1 20 D 1 21 A 1 22 A 1 23 D 1 24 D 1 25 D 1 26 C 1 27 B 1 28 C 1 29 C 1 30 C 1 31 B 1 32 C 1 33 C 1 34 B 1 35 A 1 36 C 1 37 D 1 38 B 1 39 A 1 40 D 1 Total 40

Paper 2 Section A No Answers Marks Remarks 1a P: vena cava Q: right atrium 1 1 1b contains oxygenated blood from the aorta; transporting oxygen and digested food/nutrients to heart muscles; 1 1 type content 1c oxygen dissolves in the thin layer of moisture lining the alveolar walls; oxygen diffuses from the thin layer of moisture through the alveolar walls and the capillary walls into the bloodstream; oxygen diffuses into the red blood cells and combines with haemoglobin to form oxyhaemoglobin; red blood cells carry oxygen from the capillaries to the pulmonary veins to the left atrium, followed by left ventricle, out of the heart through the aorta to the renal artery to the kidneys; 1 1 1 1 dissolves in TLM diffuse out of alveoli diffuse into RBC pathway to kidney 1d When blood vessels are damaged, damaged tissues and platelets releases thrombokinase, wh ich catalysed the conversion of prothrombin into thrombin in the presence of calcium ions; thrombin catalyses the conversion of soluble fibrinogen into insoluble fibrin threads that entangle blood cells forming a clot; 1 1 action of thrombo- kinase action of thrombin Total 10

No Answers (CLT) Marks Remarks 2ai 1 division  90 au ÷ 36 divisions = 2.5 au 6 divisions  2.5 au × 6 divisions = 15 au energy used for growth = 15 au/year 1 2aii heat/ thermal energy 1 2aiii 90 – 15 – 25 = 50 au/year 1 2b 15 90 × 100% = 16.7% 1 1 2c when rate of respiration in animals increases due to increase movement/ increase muscular contraction , animal body temperature increases, resulting in an increase in the release of heat from the body by radiation, conduction and convection; restricting movement of animals will reduce energy lost to the environment in the form of heat and increase energy available for growth; chemical potential energy in food consumed by animals will be stored and used for growth of muscle cells resulting in bigger size animals that will produce more meat when slaughtered; 1 1 1 increase heat released reduce energy lost energy for growth Total 8

No Answers Marks Remarks 3a B – salivary amylase; C – pancreatic amylase/ trypsin/ maltase/ lipase; A – pepsin; 2 2 2 3b digestive enzymes are specific in action whereby each chemical digestion is catalysed by a unique enzyme due to its three- dimensional shape; only a specific substrate can bind to the active site of enzyme to form an enzy