the effect of temperature on enzyme reaction

Aim

Studying the effects of temperature on the activity of salivary

amylase

Problem statement

What are the effects of temperature on the activity of salivary amylase on starch ?

Variable

VariableVariable Manipulated variable : temperature Manipulated variable : temperature

of the mediumof the medium Responding variable : rate of Responding variable : rate of

enzymatic reactionenzymatic reaction Constant variable :volume of saliva Constant variable :volume of saliva

(enzyme)(enzyme)

Hypothesis

The rate of the activity The rate of the activity of salivary amylase on of salivary amylase on

starch increase with the starch increase with the increase in temperature increase in temperature

until it reaches the until it reaches the optimum temperature optimum temperature

of 37 Cof 37 C

Materials

1% starch 1% starch suspension , saliva suspension , saliva solution , iodine solution , iodine solution , ice and solution , ice and

distilled waterdistilled water

ApparatusApparatus

Beakers , test tube , Beakers , test tube , syringes ,dropper , glass rods , syringes ,dropper , glass rods , white tiles with white tiles with grooves ,thermometers , Bunsen grooves ,thermometers , Bunsen burner , tripod stand , test –tube burner , tripod stand , test –tube rack ,wire gauze and stopwatchrack ,wire gauze and stopwatch

Technique

Test for the presence of starch Test for the presence of starch using the iodine test ,measure using the iodine test ,measure and record the time taken for and record the time taken for the hydrolysis of starch to be the hydrolysis of starch to be complete with a stopwatch .complete with a stopwatch .

Test for the presence of starch Test for the presence of starch using the iodine test ,measure using the iodine test ,measure and record the time taken for and record the time taken for the hydrolysis of starch to be the hydrolysis of starch to be complete with a stopwatch .complete with a stopwatch .

Procedure

1 )The salivary collected in a beaker is diluted with an equal volume of distilled water .(Rinse your mouth bef

ore collecting the saliva ) 2 ) 5ml of 1% starch suspension is added to each test tube , labelled A(1) , B(1) ,C(1) ,D(1), and E(1) respec

tively with the aid of a syringe .3 ) 2 ml of saliva solution each is add to another set of test tube , labelled A(2) , B(2) , C(2) , D(2) , and E(2)

respectively , using a new syringe .4 ) Test tube A(1) and A(2) , B(1) and B(2) ,C(1) and

C(2) , D(1) and D(2) , E(1) and E(2) are immersed respectively into five different water baths with

temperature which are kept constant at 0 C , 28 C , 37 C , 45 C and 60 C .

5 ) The test tube are left for 5 minutes .6 ) A drop of dilute iodine solution is placed into

each groove of the white tile .7 ) After 5 minutes , the starch suspension in test

tube A(1) is poured into the saliva solution in test tube A(2) .

8 ) The mixture is stirred using a glass rod . A stopwatch is activated and the time is recorded

as zero minutes .9 ) A drop of mixture from test tube A(2) is

immediately placed in the first groove of the tile containing iodine solution .

10 ) The iodine test is repeated every minute for 10 minutes .The dropper is rinsed in a beaker of

distilled water after each sampling . 11) The time taken for the hydrolysis of starch to be completed is recorded , that is , when the mixture no longer turns blue-black in colour

when tested with the iodine solution .12) The test tube containing the mixture are kept

in their respective water bath through the experiment .

13 ) Step 7 to 10 are repeated for test tube B , C , D , and E

14 .Thermometers are used to ensure that the temperature remain

constant throughout the experiment .

15 ) The results are recorded in the following table and a graph showing the rate of enzymatic reaction , 1/t against temperature (C) is plotted .

1/t against temperatureTest tube

Temperature

(C)

Time taken for the hydrolysis of starch to be completed (minutes

Rate of enzymatic reaction 1/t (min-1)

A(2) 0 No complete after 10 minutes

0

B(2) 28 2 0.50

C(2) 37 1 1.00

D(2) 45 3 0.33

E(2) 60 No complete after 10 minutes

0

Discussion

1) The test tube are immersed in their respective water bath for 5 minutes at the beginning of the experiment to allow both solution to reach the

temperature set .2) Starch is hydrolysed by salivary amylase to a

reducing sugar (maltose) .3) The Iodine solution is used to test for the presence of starch . If the iodine solution

changes from brownish-yellow to blue black , this indicates that all the starch has been

hydrolysed by the salivary amylase .

4) The graph shows that the rate of enzyme activity against temperature is a bell-shape curve .

a) At low temperature , for every 10 C increase in temperature , the rate of enzymatic reaction is

doubled .b) the maximum rate of reaction occurs at 37

C ,which is the optimum temperature for salivary amylase .

c) The average human body temperature is also 37 C .

5) At 0 C, the enzymatic is not active. Therefore, the salivary amylase cannot hydrolyse the starch .

6) As the temperature increase , the rate of enzymatic reaction increase until it reach an

optimal temperature of 37 C .7) The optimum temperature for the activity of salivary amylase is 37C . This is because the hydrolysis of starch is completed in a shorted

period . 8) Beyond the optimum temperature ,the rate of

enzymatic reaction decrease and ceases altogether at 60 C . There is no enzyme activity

at 60 C . This is because the enzyme has denatured due to the high temperature .

Conclusion

Change in temperature effect the activity of salivary amylase on

starch .Salivary amylase in inactive at 0 C and denatures at 60 C .The

rate of reaction catalysed by salivary amylase is highest at 37

C ,which is the optimum temperature .The hypothesisis

accepted.