Page 111 - Biology - XII

PROJECT - 8
Objective
To study the hydrolytic enzyme present in food items.

Principle/Theory
The enzymes are classifi ed on the nature of reaction that they catalyse. They are categorised into six
classes as follows:
1. Oxidoreductases 3. Hydrolases 5. Isomerases

2. Transferases 4. Lyases 6. Ligases

Materials Required
Starch/wheat fl our, germinating pea seedlings, beaker, funnel, test tubes, saucers/tiles, fi lter paper, tripod
stand, wire gauze, matchbox, iodine solution, mortar and pestle, and spirit lamp

Procedure
1. Take a little 5 g of starch or wheat fl our and mix it with 50 ml of boiling water in a beaker.
2. Allow the starch paste/solution to cool.
3. Take a few germinating pea seedlings (in which the radicle has grown to at least 5 cm). Remove the
seed coat and take out the cotyledons.
4. Grind the cotyledons in a mortar with water· by a pestle, and fi lter the solution.

5. On three white tiles/plates/saucers, pour little starch paste. Label them as A, B, C.
6. Leave saucer A as such, to saucer B add a few drops of iodine solution (blue colour appears), and to
saucer C add water extract of cotyledons.
7. Keep these saucers in a warm place (35–40°C). At intervals of 5 minutes or 10 minutes, test the
saucers A and C with iodine solution.

Results
1. The saucer C material gives reddish-brown colour with iodine solution. It does not show blue
colouration.

2. The saucer A material gives colour change on adding iodine solution. Note the time taken by saucer C
for the colour formation.

Dropper

Starch +
Starch
Starch + Iodine solution Cotyledon extract

(a) (b) (c)
Fig. 8.1: Enzyme action on starch

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