The set-up below illustrates a procedure that was carried out in the laboratory with a leaf plucked from a green plant that had been growing in sunlight.
(i) What was the purpose of the above procedure?
(ii) Give reasons for carrying out steps A, B and C in this procedure.
(iii) Name the reagent that was used at the step labeled D.
(iv) State the expected result on the leaf after adding the reagent named in (iii) above.
Answer:
i)
-To carry out test for starch on a leaf.
ii)
A-To kill the protoplasm of the leaf or to breakdown starch grains or to stop enzyme activity.
B-To discolour the leaf or remove chlorophyll.
C-To soften the leaf, remove any traces of ethanol.
iii)
-Iodine solution.
iv)
-On areas where starch is present, Iodine solution changes colour from
yellow/brown to black/blue black.
-To carry out test for starch on a leaf.
ii)
A-To kill the protoplasm of the leaf or to breakdown starch grains or to stop enzyme activity.
B-To discolour the leaf or remove chlorophyll.
C-To soften the leaf, remove any traces of ethanol.
iii)
-Iodine solution.
iv)
-On areas where starch is present, Iodine solution changes colour from
yellow/brown to black/blue black.
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