K.C.S.E Biology Q & A - MODEL 2012PP2QN03

K.C.S.E Biology Q & A - MODEL 2012PP2QN03

(a) In an investigation, equal amounts of water was placed in. three test-tubes labelled G, H and J. Pondweeds of equal length were dropped in each test tube. The test-tubes were then placed in identical conditions of light and carbon (IV) oxide at different temperatures for five minutes. After the five minutes, the bubbles produced in each test-tube were counted for one minute. The results were as shown in the table below.

​(i) Name one requirement for this process that is not mentioned in the investigation. 
(ii) Name the gas produced in this investigation. 
(iii) Account for the results in test-tubes H and J. 
(b) State two ways in which the human intestinal villus is adapted to its function. 

answers

​(a) (i) chlorophyll; 
(ii) oxygen; (1 mark)
(iii) Test tube H is at optimum temperature for enzyme activity; hence high rate of
photosynthesis/more bubbles. In test tube J most enzymes have been denaturedby the high temperature; hence low rate of photosynthesis/fewer bubbles. 
(b) — The villus epithelium is thin; for faster diffusion of dissolved food substances;
— The epithelium has goblet cells; which produce mucus to lubricate food passage;
— They have microvilli; which further increase their surface area for absorption;
Have lacteal; for absorption of fatty acid & glycerol/transportation of lipids;
Highly vascularised; for absorption of digested food.