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

Variable  Manipulated variable : temperature of the medium  Responding variable : rate of enzymatic reaction  Constant variable :volume of saliva (enzyme)

Hypothesis

The rate of the activity of salivary amylase on starch increase with the increase in temperature until it reaches the optimum temperature of 37 C

Materials

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

Apparatus

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

Technique

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

Procedure

1 )The salivary collected in a beaker is diluted with an equal volume of distilled water .(Rinse your mouth before 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) respectively 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 temperature Test tube

A(2)

B(2) C(2) D(2) E(2)

Temperatur Time taken for e the hydrolysis of starch to be (C) completed (minutes 0 No complete after 10 minutes 28 37 45 60

2 1 3 No complete after 10 minutes

Rate of enzymatic reaction 1/t (min-1) 0

0.50 1.00 0.33 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.