Ce Biology 1994 Paper1
CE BIO 1994
1. (a) (i) The formation of red precipitate indicates the presence of reducing sugar (glucose) in the water ------------------------------------------------------------------- 1 This shows that the dialysis tubing is permeable to glucose / permits the diffusion of glucose into the external solution ------------------------------------------ 1 (ii) (1) Increased amount of precipitates in set-up a indicates the presence of more reducing sugar ------------------------------------------------------------- 1 which comes from the hydrolysis / break down of starch ------------------------------------ 1 catalysed by the amylase / enzyme in digestive juice X -------------------------------------- 1 (2) * saliva / salivary juice -------------------------------------------------------------------------------- 1 * pancreatic juice --------------------------------------------------------------------------------------- 1 (iii) The knot of the dialysis tubing should be tied tightly ------------------------------------------------- 1 The outside of the dialysis tubing should be rinsed with distilled water before immersing into the water. Any ONE of the following : - after putting in the dialysis tubing, the water in the boiling tube should be tested for the presence of reducing sugar immediately. - the digestive juice X should be tested for the presence of reducing sugar. - the dialysis tubing should be examined for any damage. - the volume of distilled water in the boiling tube should be the same. ) ) ) ) ) any ONE------------------------------------- 1 ) ) ) ) Total : 10 marks 1. (a) (i) In the Benedict’s test, the formation of red precipitate indicates the presence of reducing sugar. However, many candidates incorrectly deduced that glucose was present. Some even came to the wrong conclusion that starch could not pass through the dialysis tubing. A considerable number of candidates stated wrongly that glucose passed out of the dialysis tubing by osmosis. These
1. (a) (i) The formation of red precipitate indicates the presence of reducing sugar (glucose) in the water ------------------------------------------------------------------- 1 This shows that the dialysis tubing is permeable to glucose / permits the diffusion of glucose into the external solution ------------------------------------------ 1 (ii) (1) Increased amount of precipitates in set-up a indicates the presence of more reducing sugar ------------------------------------------------------------- 1 which comes from the hydrolysis / break down of starch ------------------------------------ 1 catalysed by the amylase / enzyme in digestive juice X -------------------------------------- 1 (2) * saliva / salivary juice -------------------------------------------------------------------------------- 1 * pancreatic juice --------------------------------------------------------------------------------------- 1 (iii) The knot of the dialysis tubing should be tied tightly ------------------------------------------------- 1 The outside of the dialysis tubing should be rinsed with distilled water before immersing into the water. Any ONE of the following : - after putting in the dialysis tubing, the water in the boiling tube should be tested for the presence of reducing sugar immediately. - the digestive juice X should be tested for the presence of reducing sugar. - the dialysis tubing should be examined for any damage. - the volume of distilled water in the boiling tube should be the same. ) ) ) ) ) any ONE------------------------------------- 1 ) ) ) ) Total : 10 marks 1. (a) (i) In the Benedict’s test, the formation of red precipitate indicates the presence of reducing sugar. However, many candidates incorrectly deduced that glucose was present. Some even came to the wrong conclusion that starch could not pass through the dialysis tubing. A considerable number of candidates stated wrongly that glucose passed out of the dialysis tubing by osmosis. These