NYGH 2011-S3EOY-Bio Ans

2011 End-of-Year Examination Secondary Three ANSWER 1 Nanyang Girls’ High School 2011 Sec 3 BIO EOY Paper 1 Answers 1 C 7 D 13 D 19 C 25 C 2 D 8 C/D 14 B 20 B 26 B 3 C 9 B 15 B 21 A 27 C 4 A 10 D 16 C 22 B 28 B 5 C 11 D 17 C 23 A 29 C 6 A 12 A 18 B 24 D 30 B Section A A1 Fig. 1.1 shows the cross section of a dicotyledonous stem. (Flickr photo by Shihchuan 2010. Available for download under a Creative Commons license http://www.flickr.com/photos/epingchris/5110418885/in/photostream/) Fig. 1.1 (a) (i) X: phloem Y: xylem [1] Both answers correct to be awarded 1 m (ii) Sucrose and amino acids [1] Accept: ECF water and ions/dissolved mineral salts if X wrongly identified as xylem in (i) (b) Answer shown on Fig. 1.1 [3] X Y R1 can be either cortex or pith; R2 can be either cambium or intervascular cambium; R3 can be epidermis or cuticle ;

2011 End-of-Year Examination Secondary Three BIOLOGY ANSWER 2 Nanyang Girls’ High School A1 (c) (i) Structure X Structure Y http://www.mhhe.com/biosci/ http://12knights.pbworks.com/w/page/ pae/botany/histology/html/vasctis2.htm 25273875/924-State-that-terrestrial-plants The above are sample diagrams. Drawings by students do not need to be as detailed. Answer for structure X must include drawing and labeling of ‘sieve tube’ and ‘companion cell’; Answer for structure Y must include the drawing of lignin rings/spiral deposits of lignin and labeling it as ‘lignified cell wall or lignin deposits; Allow for ECF from (a) (i) [2] (ii) Valves must be inserted into structure Y + so that there will only be one directional flow of blood OR replace lignin with elastic tissue + so that they can be compressed by the skeletal muscles to assist in the flow of blood back to heart; [1] (d) (i) Obtain and observe the cross sections of a relatively large number of different species/types of dicotyledonous stems before making the drawing; [1] (ii) Allow proboscis/mouthpart of aphid pierce into structure X and then detach head of aphid to collect substances dripping through the proboscis/mouthpart Possible control: Negative control is to just detach the proboscis from aphid and check if any substances drip from it Accept if candidate described how to collect the substance without stating any control [1] [Total: 10 ] Lignified cell wall

2011 End-of-Year Examination Secondary Three BIOLOGY ANSWER 3 Nanyang Girls’ High School A2 (a) Fig. 2.1 (i) All 3 amino acids accurately circled COMPLETELY; [1] (ii) Peptide bond / amide bond; [1] Reject: “poly”peptide bond or “di”peptide bond (not a bond) (b) This polysaccharide has a compact coiled SHAPE so it occupy less space / it has a large surface area to volume ratio than all the individual (glucose) units that make up this polysaccharide; [max3] This polysaccharide can be stored because it is a large molecule with many (glucose) UNITS so it cannot diffuse through the cell membranes and be lost from the cell; This polysaccharide can be a source of energy because the (1-4 glycosidic) BONDS can be easily broken to release (glucose) units when needed for cellular respiration; This polysaccharide has its –OH groups all tucked in due to the spiral arrangement of (glucose) units so it is insoluble / osmotically inactive and can be stored; Reject: Just stating insoluble without any reference to what can be seen in Fig 2.2 (c) Both answers are acceptable - Yes, because the (glycogen) has a branched structure unlike the coiled/unbranched/linear structure of starch (amylose form) in Fig. 2.2; No, because both starch (amylopectin form) (less branching) and glycogen have branched structures; No need to identify the polysaccharide. Do not repeat Q about bonds. [1]

2011 End-of-Year Examination Secondary Three BIOLOGY ANSWER 4 Nanyang Girls’ High School A2 (d) (i) Phospholipid; [1] (ii) Allow Error Carried Forward from d(i) Change to the physical property = Now the phospholipid has both a hydrophilic region and a hydrophobic region / amphipathic molecule / amphiphatic molecule instead of being totally hydrophobic; [1] Explanation = The phosphate group forms the hydrophilic head of the phospholipid; The two fatty acid/hydrocarbon tails forms the hydrophobic tails of the phospholipid; [max2] Allow for ECF from (d) (i), but answers must be reasonable and sound. [Total: [10] A3 (a) Compare: Both do not need the use of energy/energy from respiration/are passive transport processes; [any two] Accept = Molecules move down a concentration gradient Contrast: Osmosis only occur for water molecules unlike diffusion; Osmosis occur in the presence of a partially/selectively permeable membrane unlike diffusion which can happen with or without the partially permeable membrane; Reject: semi-permeable Note: Answer for contrast between diffusion and osmosis should compare two similar characteristics instead of giving the definition of each process. (b) (i) Endocytosis occurs; Accept: Phagocytosis / Invagination [2] The amoeba is able to fold the cell membrane around the ciliate to form a (food) vesicle / OWTTE; Accept: The amoeba engulfs and ingests the ciliate and forms a (food) vacuole / phagosome within its body (ii) Exocytosis occurs; [1] Accept: Saprophytic nutrition / Extracellular digestion Reject: Chemical digestion (answer is vague) A3 (c) (i) Method = Facilitated diffusion; [3] TWO reasons = Diffusion because glucose molecules move from high concentration to low concentration / across concentration gradient; Facilitated because there is the presence of a carrier protein / transport protein to speed up movement of glucose molecules; Reject = Channel protein (the protein in Fig 3.2 has changed its shape), No need for energy (cannot tell from Fig 3.2) (ii) Increase the number of (carrier) proteins (in the cell membrane); Increase number of carriers increases the number of glucose that can bind to the carriers per unit time / rate of glucose molecules being transported by the proteins; Accept: Active transport (only if answer has explained that it is an additional process to facilitated diffusion) Reject: increase rate of glucose taken in by the cell (repeating question) Reject: increase temperature (structure is a cell) [2] [Total 10 ]

2011 End-of-Year Examination Secondary Three BIOLOGY ANSWER 5 Nanyang Girls’ High School 4 (a) Q – coronary artery; Accept: coronary vein Reject: capillary/ies [1] (b) [1 mark for each correct set] (c) (i) R – endothelium / inner folded wall / tunica intima S – elastic tissue / elastic fibres / muscular tissue / smooth muscles / tunica media [1 mark for 2 correct] (ii) vein will have thinner less muscular walls / wider lumen / presence of valves Accept: the tunica media and tunica adventitia in the vein are indistinct [any two] (iii) larger surface area to vo