Answer to Written Practical Question (Hands on Pg 40)

1a)

Set	Time taken (min)
A	20
B	10
C	3
D	6
E	30

b)(i) Observation 1-The time taken for complete hydrolysis of starch in set C/at 37oC is 3 minutes.
Observation 2-The time taken for complete hydrolysis of starch in set E/at 50oC is 30 minutes.
(ii) Inference 1 -The time taken for complete hydrolysis of starch in set C is fastest because 37oC is the optimum temperature for enzyme activity.
Inference 1 - The time taken for complete hydrolysis of starch in set E is the slowest because at too high temperature, that is 50oC, enzyme are denatured.

c)

Variable	Method to handle the variable
Manipulated variable Temperature	5 sets of apparatus using water baths of different temperatures, 15oC, 25oC, 37oC, 45oC and 50oC are set up.
Responding variable Time taken taken for complete hydrolysis of starch	Measure and record the taken for complete hydrolysis of starch using a stopwatch
Fixed variable pH// enzyme concentration// substrate concentration	Fix the pH to be the neutral throughout the experiment Fix 1ml of saliva throughout the experiment Fix 5 ml of starch throughout the experiment

d) The higher the temperature, the higher the rate of enzyme reaction until an optimum temperature is reached.
e)

Temperature (oC)	Time taken for hydrolysis of starch (minutes)	Rate of reaction (min -1)
15	20	0.05
25	10	0.10
37	3	0.33
45	6	0.17
50	30	0.03

f) An increase in temperature will also increase the rate of reaction until the optimum temperature of 37oC is reached. The rate of reaction decreases after 37oC.
g)An enzyme/amylase hydrolyses starch into a product that make the iodine solution remains unchanged/yellow, and the rate of reaction is affected by temperature.
h)The rate of reaction will be zero because all enzymes are denatured at high temperature of 70oC.