SJI 2017 Bio Prelim P2 MS

St Joseph’s Institution Preliminary Examination 2017 SJI Sec 4 Biology OP Page 2 of 6 PAPER 2 SECTION A QN NO. SUGGESTED ANSWER SCHEME 1(a) - Polypeptide: a straight/unfolded molecule made up of/with sequence of amino acids. - Protein is a folded form of polypeptide which performs a specific biological function. 1(b) - Glycogen is a storage form of glucose/sugar in animals. - Glucagon is a hormone which breaks down glycogen to glucose during homeostasis. - Glycerol is a component of fats/with fatty acids. 2a - Sketch of graph showing a lower rate of reaction but same trend as Fig. 2.1. 2b - Enzymes involved in photosynthesis start to denature due to high temperature; - Less molecules/amount of enzyme-substrate complex/products can be formed peer unit time. Rate of reaction reduces. 2c - More energy available to enzymes and substrate molecules; - Increased KE for the molecules; - Higher frequency of formation of enzyme-substrate complex thus higher rate of products formed. 3a - Being small increases surface to volume ratio. - This increases rate of diffusion/therefore better absorption of gas by diffusion. 3b(i) X = hydrogen carbonate ion/bicarbonate ion; Enzyme = carbonate anhydrase 3b(ii) - Both A and B are one-celled thick/moist/ covered with a layer of moisture. 3b(iii) (0.04 + 0.02 + 0.05)um = 0.11 um 3c - Diaphragm relaxes and arches/bends upwards; - internal intercostal muscles contract; - causes the ribcage to swing downward and inward; - this increases the lung pressure/thoracic cavity pressure to force air out. 4a - Cell Y produces antibodies to kill/agglutinate the germs/neutralise the effects of germs; - Cell X will carry out phagocytosis to engulf the germs. 4b - Platelets and damaged cells causes thrombokinase to increase; - Thrombokinase causes fibrinogen to form fibrin to trap blood cells and germs which is the blood clot.

St Joseph’s Institution Preliminary Examination 2017 SJI Sec 4 Biology OP Page 3 of 6 QN NO. SUGGESTED ANSWER SCHEME 5a - Fallopian tube/oviduct. 5b - Fertilisation still takes place/there is still fusion of sperms and eggs/fusion of male and female gametes still occurs. 5c - The embryos will form placenta in the uterus; - this allows for exchange of gases between mother and embryo; - placenta allows nutrients and waste products exchange at placenta; - amnion/amniotic sac can be formed to allows embryo to grow freely and protected from physical injuries/cushion the fetus against mechanical injuries. 6a 6b - Plankton population will increase; - Mackerel population will decrease. 6c - Plant plankton will absorb the mercury and bioaccumulate in the tissues; - when animal planktons consume them, the mercury is passed to the animal planktons; - since the mercury is not removed, the concentration bioamplify. - When humans consume the mackerel the human may be poisoned. Plant plankton Animal plankton Macker