NYGH 2015-S3EOY-Bio P1 and P2 ans

1 NANYANG GIRLS’ HIGH SCHOOL End-of-Year Examination 2015 Secondary Three BIOLOGY Paper 1 1 B 7 C 13 A 19 C 25 A 2 C 8 B 14 D 20 A 26 C 3 C 9 D 15 B 21 B 27 C 4 D 10 A 16 C 22 C 28 D 5 B 11 A 17 C 23 C 29 D 6 C 12 B 18 C 24 B 30 D Qn Answer Explanation 1 B The functions of mitochondrion is to release energy by oxidising glucose to release energy molecules; ribosome is to synthesise protein; vacuole is to store substances such as water and food substances; and rough endoplasmic reticulum is to transports proteins to the Golgi apparatus, hence is answer is B. 2 C P – chloroplast; Q – cell wall; R – nucleus; S – mitochondrion; T - large central vacuole R & S are common features found in an animal cell. In the options given, only C, which are R & S, are features found in an animal cell. 3 C Water moves from a region of less negative (more water) to a region of more negative(less water). 4 D Active transport is the process in which energy is used to move the particles of a substance across a membrane against its concentration gradient, that is, from a region where the particles are of lower concentration to a region where they are of higher concentration. In the sodium ions (Na + ), the ions move out of the cell to the plasma, hence explains the low number (18) in the cell and high number (149) in the plasma. In the potassium ions (K + ), the ions move from the plasma into the cell, hence explains the low number (6) in the plasma and high number (154) in the cell. Chloride ion moves by facilitated diffusion. Hence, the answer is D. beaker thistle funnel direction of net water movement Increase / decrease of water level in thistle funnel A 5% sucrose (more negative) distilled water (less negative) thistle funnel to beaker decrease B 10% sucrose (more negative) 5% sucrose (less negative) thistle funnel to beaker decrease C 5% sucrose (less negative) 10% sucrose (more negative) beaker to thistle funnel increase D distilled water (zero negative) distilled water (zero negative) no net movement same

2 5 B The diagram shows a lipid molecule / triglyceride. A lipid molecule is made up of a glycerol molecule and 3 fatty acids. Hence B is the answer. 6 C When the temperature increases by 10 °C (from 20 °C to 30 °C), the rate of reaction increases. Hence the likely amount is 0.45 g. 7 C Benedict’s test is a test for reducing sugar; biuret test is a test for protein; ethanol emulsion test is a test for fat, and iodine test is a test for starch. Food that shows presence of both food protein and starch will show positive for biuret test and iodine test, hence the answer is C. 8 B At low temperature, enzyme activity is low but increases as temperature rises till an optimum is reached (most enzymes have the optimum temperature of about 40 °C to 45 °C). Above the optimum temperature, enzyme activity decreases as enzymes become denatured. 9 D Amylase digests away starch. During the iodine test, it will show brown indicated by the zone around the well (i.e. starch is absent / digested away by salivary amylase). In solution IV, pH 6.5 does not interfere the action of salivary amylase, so it will digest starch and the zone around the well will be brown. In solutions I and III, pH 5 and alkali pH 7.5 affect the action of amylase, so amylase will not digest starch as much as solution IV. Both zones showing brown should be similar in diameter to each other. In comparison, solution IV will have the widest zone showing brown, hence well Y. Solutions I and III can be either X and Y or Y and X. In solution II, amylase is denatured by strong acid, so it cannot digest starch. Thus the area outside the well will show blue-black (i.e. starch is present). Hence the well should be W. In considering all these, the answer is D. 10 A Photolysis of water gives oxygen (P) and hydrogen ion (Q). The hydrogen ion (Q) produced in photolysis is used to reduce carbon dioxide (R) to carbohydrates such as glucose (C6H12O6) (given), giving water as a by-product (S). 11 A Only certain wavelengths of light are used for photosynthesis by pigment X. Light of blue and red wavelengths are most effectively absorbed by pigment X and produce the highest rates of photosynthesis. Hence the answer is A. 12 B Light of green wavelength produces the lowest rate of photosynthesis, hence the answer is B.

3 13 A As the distance between the water plant and lamp increases, rate of photosynthesis decreases. 14 D The brown colouration indicates absence of starch, hence, region of light green leaf. The blue-black colouration indicates presence of starch, hence, region of dark green leaf. The centre where it showed brown must be where the black paper was placed (no light absorbed in this area, hence no photosynthesis occurred and therefore no starch made, showing brown upon iodine test). 15 B The xylem tissue can be described as a ‘star’ shaped structure at the centre of the root, and the phloem tissue is found between the arms of the xylem tissue. The epidermis of the root is the outermost layer of cells. 16 C Cell 1 is an epidermal cell, which does not contain chloroplast. Cell 2 is palisade mesophyll cell; Cell 3 is spongy mesophyll cell; and Cell 4 is a guard cell. These cells contain chloroplasts and therefore photosynthesise. 17 C The stronger the wind, the higher the rate of transpiration. 18 C Still room: 0.6 – 0.1 = 0.5 0.5 x 1 = 0.5 0.5 X 2 = 1.0 cm3 per hour light: 0.8 - 0.1 = 0.7 0.7 x 1 = 0.7 0.7 X 2 = 1.4 cm3 per hour fan: 1.1 – 0.1 = 1.0 1.0 x 1 = 1.0 1.0 X 2 = 2.0 cm3 per hour 19 C Structure 1 is trachea. Structure 2 is esophagus. Structure 3 is small intestine. Structure 4 is large intestine. Trachea is part of the respiratory system and does not experience peristalsis. The structures that have peristalsis are 2, 3 and 4. Hence answer is C. 20 A Structure P is a lacteal / lymphatic capillary, functions to transport fats. Structure Q is the villus, which consists of epithelial cells having numerous microvilli to increase surface area to volume ratio to absorb nutrients

4 21 B The amino group is converted to ammonia (P) and converted into urea (Q), which is removed in urine. The carbon residue is converted into glucose (X) and converted into glycogen (Y), which is stored in liver and muscles. 22 C In the absence of oxygen, the absorption of glucose dropped from 6.4 to 2.5 arbitrary units. Likewise for amino acids, the absorption of amino acids dropped from 5.7 to 1.9 arbitrary units. These showed that glucose and amino acids are absorbed by active transport, which requires oxygen. However, in the absence of oxygen, absorption of glycerol and fatty acids are not affected. 23 C Starch is not digested in the stomach and colon. It is only digested in the ileum (in this question). Hence the answer is C. 24 B Recipient 1: Recipient’s blood group A has antibody b in serum; when recipient receives donor’s blood which is B (presence of antigen B), antibody b (recipient) will bind to antigen B (donor’s red blood cell). Hence there will be agglutination. Recipient 3: Recipient’s blood group O has both antibodies a and b in serum; when recipient receives donor’s blood which is AB (presence of antigens A and B), antibodies a and b (recipient) will bind to antigens A and B (donor’s red blood cell). Hence there will be agglutination. 25 A Low plasma potential and low blood pressure pull water into the venous end. As substances leave the blood plasma, its water potential decreases. This enables water to enter by osmosis at the venous end when the tissue fluid has a higher water potential. As blood flows through the capillaries, its pressure decreases. 26 C C is the median septum. Median septum runs down the middle of the heart and prevents the mixing of deoxygenated blo