2013 GCE O Level Bio Suggested Answer

2013 GCE O Level Biology Suggested Answer Paper 1 1 2 3 4 5 6 7 8 9 10 B C C D D A D C D C 11 12 13 14 15 16 17 18 19 20 C D A A D B C C B D 21 22 23 24 25 26 27 28 29 30 D B A C B B B A B B 31 32 33 34 35 36 37 38 39 40 B B D C C D C B B A Paper 2 (Section A) 1 (a) (i) P: Right atrium [1] Q: Chordae tendineae [1] (ii) Correctly labelled [1] (b) Blood from the pulmonary vein enters the left atrium of the heart as the muscle of the left atrium relaxes [1]. The muscles of the left atrium then contracts and blood is pushed through the bicuspid valve into the left ventricle [1]. The muscles of the left ventricle then contracts, causing an increase in the pressure of the ventricles. This causes the bicuspid valves to close to prevent the backflow of blood and the semi -lunar valves in the aortic arch to open [1]. This forces blood from the left ventricle and out of the heart into the aorta [1]. (c) (i) 0.3 seconds [1] (ii) Line 2 [1] 2 (a) Translocation is the transport of manufactured food substances like sugars and aminio acids [1] in the phloem of plants. [1] (b) (i) Correctly labelled (recognise thicker walls lined with lignin) [1] (ii) Correctly labelled (phloem on outer ring) [1] Questions to note: 15, 21, 25, 35, 36, 37 Question to note: 1ai, 3, 5a, 5b, 6bii, 8bii, 9, 10, 11O

(c) As weedkillers are applied to the soil, they can dissolve in soil water surrounding the root hair cells of the weeds [1]. The weedkiller then diffuses into the root hair cells of the plant, increasing the concentration of weedkiller in the cell sap of the root hair cells [1]. The weedkiller then diffuses from cell to cell in the roots until it reaches the xylem vessel [1]. The weedkiller is then transported up the xylem to the leaves of the plant and finall y diffuses into mesophyll cells containing chloroplasts, which is the site of action of the weedkillers [1]. 3 (a) Branch of renal artery/ arteriole (b) (i) Protein: 0.0 Glucose: 0.1 (ii) Proteins are large molecules transported in blood and unable to pass through the basement membrane during ultrafiltration [1]. Hence, there is an absence of proteins in R which is the collecting duct as proteins are not filtered into the nephrons [1]. (iii) Glucose are small molecules that pass into the nephron during ultrafiltration hence it is present at Q which is the Bowman’s capsule. However, all glucose molecules are selectively reabsorbed into the bloodstream at the proximal convoluted tubules. Thus, there is no glucose present at R [1]. (c) ADH increases the permeability of walls of the collecting ducts to water [1]. This causes more water to be reabsorbed into the bloodstream during selective reabsorption [1]. This results less water passing through region R as urine; with a smaller volume of urine, the urine also becomes more concentrated [1]. 4 (a) Activation energy is the minimum energy requir