NYGH 2012-S3EOY-Bio Ans

1    NANYANG GIRLS’ HIGH SCHOOL End-of-Year Examination 2012 Secondary Three BIOLOGY Paper 1 1 D/B 7 A 13 C 19 A 25 B 2 C 8 C 14 D 20 C 26 D 3 A 9 B 15 D 21 C 27 D 4 B 10 C 16 D 22 C 28 D 5 B 11 A 17 B 23 B 29 A 6 B 12 B 18 A 24 C 30 A Paper 2 - Section A Qn Answers Marks A1a Controls movement of substances into and out of a cell / partially permeable membrane / selectively permeable membrane (reject: semi-permeable) 1 A1b(i) Cell-cell recognition; protein channels for transport of substances; enzymatic activity / protein transporters ; signal transduction; attachment of cytoskeleton and extracellular matrix; act as receptors; aid in facilitated diffusion; aid in active transport; allows diffusion of polar substances; (any 1) 1 A1b(ii) Protein markers from mouse and human were mixed in the hybrid / markers' distributions were not separated / showed mosaic pattern / various proteins embedded in the structure; Lateral movement of proteins occurred / proteins were mobile / proteins could move within the membrane / positions of the proteins are not fixed / ability of two separate cells to fuse into a bigger cell; 2 A1c(i) Higher temperature results in increased amount of cholesterol / Lower temperature results in decreased amount of cholesterol; 1 A1c(ii) Membranes becomes more fluid at warmer temperatures; Cholesterol maintains stability of membrane / maintains integrity of membrane / prevents deformation / prevents disintegration ; Cholesterol helps to make the membrane less fluid at higher temperatures; Restrains movement of phospholipds / Less movement of phospholids; (any 2) 2 2    Qn Answers Marks A1d Diffusion Facilitated diffusion Transport proteins / carrier proteins are not involved Transport proteins / carrier proteins are involved Mainly for the transport of hydrophobic substances Mainly for the transport of hydrophilic substances Non-specific Specific due to carrier proteins Mainly for transport of non-polar substances Mainly for transport of polar substances May occur with or without membrane Occurs across a membrane (any 2) 2 A1e Contractile vacuole would be less active / will not function [OWTTE]; (must have) Less water absorption in isotonic environment; hence less water is required to be pumped out by the contractile vacuole; Water potential gradient is less steep in isotonic environment; Water potential is same; No net movement of water molecules; (any 1) 2 A2a(i) 1 A2a(ii) Adding an enzyme speeds up the reaction/increases the rate; AND as less energy is required for the reaction to progress / complete; addition of enzyme lowers activation energy; Reject: catalysing the reaction 2 A2b(i) Boiled ginger juice did not curdle/coagulate / curdle slower the milk while raw ginger did; Reject: clumping/clotting of milk, raw ginger milk will curdle better 1 A2b(ii) Protease / rennin in the ginger juice is denatured when boiled; The active sites of the protease / enzyme (ECF) can no longer bind to the milk proteins / The 3-D conformation of the protease has changed; Reject: kill protease / protease died 2 Ea

3    Qn Answers Marks A3a Chloroplast is compartmentalized for more efficient running of light dependent and light independent stages [OWTTE]; Enzymes for light dependent stage / light stage / photolysis of water are located in thylakoid / grana; Chlorophyll is located in grana to absorb light for photosynthesis/photolysis; Enzymes for light independent stage / dark stage / reduction of carbon dioxide into glucose are located in stroma; Water transport channels in membranes of chloroplast allow water to enter the organelle for photosynthesis; Double membrane allows transport of glucose out of the chloroplast; Thylakoid membrane / grana has high SA:VR to absorb more light; [any 3] Reject: Chloroplast is round and flat to increase SA:VR, allow substances to diffuse in and out of the chloroplast 3 A3b(i) It is the same lamp / in the same position for all experiments ; We are not investigating light intensity in this experiment; It is a constant variable; Does not change the temperature significantly; 1 [any 1] A3b(ii) Remove Bunsen burner – do not heat directly; Do not add ice-cubes directly into beaker/ use ice pack; Use a water bath to regulate temperature ; Repeat the experiment 3 times / have 3 replicates ; Have a control with no plant ; Use sodium bicarbonate to provide carbon dioxide, not calcium hydroxide; Use (inverted funnel with) inverted measuring cylinder to measure oxygen volume; Do not use thermometer as a stirrer; Use a datalogger; Narrow the intervals from 10degrees to 5 degrees C [must state #]; Cover beaker to prevent evaporation and concentration of solution; Have same mass of elodea plant for each setup; Allow 5-10 min for elodea to adjust to new temperature before counting; 4 [any 4] A3c Thin cuticle indicates that water loss is not an issue (as it is submerged); / allows gases/water to diffuse in and out easily; / allows light to pass through easily Chloroplasts in epidermis (no mesophyll layers) indicate that it must absorb max / more sunlight in a place that receives less light; Undeveloped xylem/ few xylem seen as water transport system reduced to minimum / cells possibly receive water direct from environment; / does not require mechanical support in water; No stomata seen – because plant does not need to release gas as it does not come into contact with any; No intercellular air space as it is fully submerged and air is less dense / it does not require gaseous exchange; Only 2 layers of cells to allow rapid diffusion of gases / water; Thin epidermis to allow rapid diffusion of gases; [any 3] 3 max 4    Qn Answers Marks A4a or 1 A4b(i) X: Red blood cell / Erythrocyte; Z: Platelet / Thrombocyte 1 A4b(ii) Entry of bacteria/pathogens/disease-causing microorganisms into the body / infections; Tissue rejection due to incompatibility; Y (White blood cell / phagocyte) protects the body by phagocytosis / engulfing and ingesting the foreign substances / production of antibodies; Transplant of bone marrow; White blood cells are produced; [any 2] 2 A5a(i) 1m – logical model drawn is workable; 1m – diagram shows chest wall + lungs + diaphragm; 1m – At least 3 labels to show what each structure represents in the human system  glass jar / plastic bottle = chest  plastic bag (cut) / rubber sheet = lungs  straw = trachea / bronchi  opening to bottle = mouth / trachea Reject: if glass jar / bottle has an opening that is not sealed Reject: if glass jar / bottle is completely sealed Reject: if straws have gap into chest cavity Examples of possible models: 3 Opening (mouth) balloon (lungs) Jar / bottle (chest) straw (trachea / bronchi) Rubber sheet / plastic bag (diaphragm)

5    Qn Answers Marks A5b(ii) Your model Human respiratory system Similarity Lungs expand as diaphragm / sheet is lowered; 2 lungs are represented (if model shows it); Trachea and bronchi are represented (if model shows it); Mouth is represented (if model shows it); [max 1] Difference Diaphragm is flat; Intercostal muscles are not shown; Ribs / sternum not shown; Alveoli are not shown; Glass jar does not expand; [max 1] [statements must be in full sentences, and comparing the same things] Diaphragm is curved at rest; Intercostal muscles are present; Ribs / sternum are present; Alveoli are present; Chest wall can expand / Sternum ;moves up and down / rib cage can move; 2 A5c Mr Tan you are feeling tired because you are taking in less oxygen due to shortness of breath; Oxygen is required for respiration (which generates energy) / oxidation of food substances; Yo