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 Mackerel Human

St Joseph’s Institution Preliminary Examination 2017 SJI Sec 4 Biology OP Page 4 of 6 QN NO. SUGGESTED ANSWER SCHEME 7a - The antibodies a, b from the donor will be diluted by the plasma of the recipient. 7b - 6 7c - Genetic diagram: Parental phenotype: A x B Parental genotype: IAIO x IBIO Gametes (circled): IA IO IB IO Random fertilization: Offspring genotype: IAIB IAIO IBIO IOIO Offspring phenotype: AB A B O 8a - 6 8b - it holds the sister chromatids together. - spindle fibre attaches to x to pull the chromatids apart during metaphase. 8c - Correct pair of chromosomes (of same lengths) are shaded. 8d - Three non-homologous chromosomes. 8e(i) - The R. imitator has the similar body patterns as the R. variabilis. - The predators assume that they are also toxic so R. imitators are not preyed on. 8e(ii) Variation produced patterns on body similar to R. variabilis these frogs survived during natural selection (not preyed on) breed / genes passed to next generation

St Joseph’s Institution Preliminary Examination 2017 SJI Sec 4 Biology OP Page 5 of 6 PAPER 2 SECTION B QN NO. SUGGESTED ANSWER SCHEME 9a - Chemical messenger - secreted by endocrine gland - directly into blood stream - effect changes in target organs 9b Any one of: - Both A and B must empty their bladders at the start of the experiment to ensure that all urine collected is the result of drinking water or the solution during the experiment. /OR - Both A and B had same physical activities to ensure loss of fluid through sweating is about the same. 9c(i) Curve Y 9c(ii) - Consumption of salt causes decrease in water potential in blood - this stimulates the hypothalamus to send nerve impulses to pituitary gland - pituitary gland secretes more ADH (antidiuretic hormone) - The hormone increases permeability of the collecting duct of kidneys to increase reabsorption of water into blood 9d - The skin 9e - Excretion removes metabolic wastes or toxic substances out of the body - if these substances were to remain in the body the water potential/ pH in blood may be upset - blood cells may be damaged/enzymes may not work at optimum conditions - high concentration of toxic substances may kill the person. 10a - It is a double-helical molecule/structure - Made up of nucleotides/polynucleotides - the two strands are bonded together by complementary base-paring - of nitrogenous bases: A-T (Adenine-Thymine); C-G (Cytosine-Guanine) - it contains genes 10b - a gene for insulin is identified and cut using restriction endonuclease/restriction enzyme - a plasmid of an E coli/bacteria is cut using the same restriction enzyme - the two ends of the gene produce ‘sticky’/complementary ends with the insulin gene - the insulin gene is joined with the plasmid using DNA ligase - bacteria are treated with heat/electric shock to cause the cell surface membrane to open up - recombinant plasmid is transferred into bacteria to form transgenic bacteria - Transgenic bacteria allowed to multiply to produce insulin in mass

St Joseph’s Institution Preliminary Examination 2017 SJI Sec 4 Biology OP Page 6 of 6 11 EITHER (a) - Some energy is lost when it is being transferred from one organism to another in a food chain/in ecosystem - the energy loss is can be in the form of heat energy lost to the environment - during respiration in organisms - energy locked in the egested or excreted products not passed to the organisms in next trophic level - some of the organic materials are not consumed by organisms and is not passed on in the food chain - these account for a decreasing in energy down the food chain and not restored/recycled completely in the ecosystem - having a shorter food chain allows more energy to be passed to the organisms in the next higher trophic level (b) - Glucose is oxidized during respiration to release energy in organism - water and carbon dioxide are the by-products of respiration - carbon dioxide is absorbed by green plants/producers during photosynthesis - carbon atoms are used to form glucose during the process - Glucose may be converted to protein or fats in plants which may be passed on to animals when being consumed 11 OR (a) - Water and mineral salts/nitrates are being transported - by the xylem vessels from the roots up the stem - mainly by transpiration pull - These materials are transported upwards to the leaves - Glucose formed during photosynthesis is converted to sucrose and amino acids - sucrose and amino acids are translocated by phloem tissues from leaves to other parts of plant - energy and sucrose are loaded into sieve tube cells for translocation - energy is provide by companion cells (b)(i) - the guard cells will plasmolyse - they become flaccid resulting in decrease in stomatal pore (b)(ii) Adv