K.C.S.E Biology Q & A - MODEL 2015PP2QN04

K.C.S.E Biology Q & A - MODEL 2015PP2QN04

In an experiment to investigate a factor affecting photosynthesis, a potted plant which had been kept in the dark overnight was treated as shown in the diagram below and exposed to light.

​(a) Why was the potted plant kept in the dark overnight’? 
(b) Which factor was being investigated in the experiment? 
(c) (i) Which test did the students perform to confirm photosynthesis in the leaves labelled P and Q? 
(ii) State the results obtained in the leaves labelled P and Q.
P             
Q              
(iii) Explain the results obtained in the leaves labelled P and Q. 
P
Q           
(d) What was the purpose of leaf Q in the experiment?

ANSWERS

(a) To destarch/remove starch from the leaves; 
(b) Carbon (IV) Oxide/CO2;
(c) (i) Test for starch; 
(ii) p - Retained the colour of iodine solution/brown/yellow; 
Q - Turned blue-black/black/dark-blue;
(iii) P - Did not photosynthesize /no starch is formed because Sodium Hydroxide pellets absorbed Carbon (IV) Oxide;
Q - Photosynthesized /starch was formed because Carbon (IV) Oxide was in the flask;
(d) Control (experiment);