K.C.S.E Biology Q & A - MODEL 2011PP2QN01

K.C.S.E Biology Q & A - MODEL 2011PP2QN01

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. 
A
B
C
(iii) Name the reagent that was used at the step labelled D. 
(iv) State the expected result on the leaf after adding the reagent named in (iii) above. 

ANSWERS

​(i) - Testing a leaf for the presence of starch;
(ii) - A - kill the leaf/break down cells/stop enzymatic activity;
B - Removal of chlorophyll;
C - Soften leaf/makes leaf less brittle;
(iii) Iodine solution;
(iv) Areas where starch is present stain blue/blue black;