2016 GCE O Level Bio Suggested Answer JEN

2016 GCE O Level Biology Suggested Answer Paper 1 1 2 3 4 5 6 7 8 9 10 D A D D A B B B C D 11 12 13 14 15 16 17 18 19 20 A B C C C B B C B C 21 22 23 24 25 26 27 28 29 30 D D C D C D B D C B 31 32 33 34 35 36 37 38 39 40 C C D A A C A C C B Paper 2 (Section A) 1 (a) A: fibrin threads [1] B: red blood cell [1] (b) When blood vessels are damaged, damaged tissues and blood platelets release thrombokinase. Thrombokinase enzyme converts prothrombin protein present in blood plasma to thrombin in the presence of calcium ions [1]. Thrombin then catalyses the conversion of soluble fibrinogen to insoluble threads of fibrin [1]. The fibrin threads th en entangle blood cells to form a blood clot that prevents the entry of microorganisms [1]. (c) When arteries in the brain become blocked by the blood clot, oxygen and glucose cannot be supplied by blood to the brain cells [1]. Brain cells cannot respire to release energy for cellular activities without oxygen and glucose [1]. This can lead to the death of brain cells, affect the function of part of the brain and a stroke may occur [1]. 2 (a) Salivary amylase [1]; polypeptides [1]; small intestine and pancreas [1] (b) Enzyme in mouth: B [1]. The saliva in the mouth is neutral and this makes the mouth neutral too. Hence the enzyme salivary amylase works best at pH 7. [1] Enzyme in stomach: A [1]. The stomach contains HCl making it acidic. Thus, the enzyme pepsin works best at pH2 [1]. 3 (a) A mutation is a sudden random change in the structure of a gene or in the chromosome number [1]. (b) (i) Individual 1: dd [1] Questions to note: Question to note: 1a, 3, 5a, 5b, 6bii, 8bii, 9, 10, 11O

Individual 2: Dd [1] (ii) Individual 3: Pp [1] Individual 4: pp [1] (iii) 50 % 4 (a) (i) Root hairs [1] (ii) The root hairs help to absorb water [1] and dissolved mineral salts [1] from the soil. (iii) The root hairs are long and narrow protrusions of root hair cells that help to increase the surface area to volume ratio [1] so that absorption of substances can be done at a faster rate [1]. (b) Xylem [1] helps to transport water and dissolved mineral salts from the roots to the leaves. It also contains deposits of lignin that provide mechanical support for the plant [1]. 5 (a) (i) A: mitochondrion [1] B: smooth endoplasmic reticulum [1] (ii) It is the site of cellular respiration to release energy for cellular activities. (b) 1. The plant cell has a cell wall but an animal cell does not have a cell wall [1]. 2. A plant cell has chloroplasts but an animal cell does not have chloroplasts [1]. 3. A plant cell has one central, large, permanent vacuole but an animal cell has many small, temporary vacuoles [1]. 6 (a) 1: fruit bats [1] 2: banana plants [1] One arrow from banana plants to monkeys [1] One arrow from macaws to pythons [1] (b) Trophic level is the feeding position of an o