To Study The Action of Salivary Amylase on starch | Biology Practical Class 12

 To Study the Action of Salivary Amylase on Starch.

Aim:-

To study the action of salivary amylase on starch.

REQUIRMENTS:-

Measuring cylinder, test tube, test tube stands, beakers, funnel, water bath, spirit lamp, pipettes, starch, cotton, sodium chloride, iodine, potassium iodide, paraffin wax, marker, etc.

PREPARATION OF REAGENTS:-

1.    Lugol's iodine solution:-     Take iodine 1 g. potassium iodide 2 g and 100 ml. distilled water; mix and allow to stand. Deep this solution in glass bottle.

2.    1% NaCl Solution:-     Dissolve 1 g NaCl in 100 ml distilled water.

3.    1% starch solution:-     Take about 0.5 g of starch in a 100 ml. beaker and add enough water to make a paste dilute the paste by adding 50 ml. water and boil for about 5 minutes. Leave the solution overnight and filter it to get 1% starch solution.

COLLECTION OF SALIVA:-

Make a thin film of cotton and dip it into water. Drain off the water of the cotton and spread it over the mouth of funnel in such a way that it acts as filter. Deep the funnel over a clean test tube. Now, chew a piece of rubber and pour the incoming saliva into the funnel. Filtered saliva will collect in the test tube. Take 1 ml. of saliva and add 19 ml. of water to get 1 : 20 dilution of the enzyme.

PROCEDURE:-

1.    Prepare series of test tubes having 1 ml. of iodine solution in each. Make two sets of iodine tubes and deep them in stands.

2.    To test tube add 5 ml of 1 % NaCl. Label it as experiment tube. To another tube add 5 ml. of 1 % starch solution and 1 ml. of 1 % NaCl solution. Label it as control tube.

3.    Put both these tubes in a water bath set at 37' C for about 10 minutes.

4.    To the experimental tube, add 1 ml of diluted enzyme and to the control tube add 1 ml of water. Immediately take a drop each form these test tubes and add to the tubes having iodine.

5.    Note, the time of adding as zero minute reading. Deep both experimental and control tubes in water filled beaker throughout the experiment.

6.    After 2 minutes, repeatedly take a drop of solution and add to the iodine tubes and note the change of iodine color.

7.    compare the series of experimental iodine tube with the control iodine tube.

8.    Perform Benedict' test for both the experiential and the control tubes. Only the experimental tube will develop orange color on heating.

OBSERVATION:-

Show time required to get the end point in digesting 5 ml. of 1 % starch at 37'C by the diluted enzyme.

                                                            OBSERVATION TABEL

RESULT:-

It takes........ minutes for 1 ml. of diluted enzyme (1 :20 dilution) to digest completely 5 ml, of 1 % starch solution to the end point (achromic point).

CONCLUSION:-

The enzyme salivary amylase present in saliva acts on starch and converts in into maltose (a disaccharide) starch gives blue color with iodine.

In the control tube, we have only starch and Nacl. Instead of enzyme. 1 ml  of water has been added. Therefore, in this tube starch is not digested to maltose. Hence. Blue color deeps coming with iodine solution.

Whenever, in the experimental tube, we have starch and enzyme both, Nacl acts as an activator of the enzyme. The enzyme gradually acts on starch and converts it into maltose. Starch keeps on giving blue color with iodine till is is completely digested into maltose. So, at this point no blue color is formed. This is the end point or "Achromic point".

PRECAUTIONS:-

1.    Always filter the saliva through a wet cotton thin film and not through a filter paper.

2.    While measuring the saliva, there should be no air bubble.

3.    Maintain the temperature i.e. 37'C thoroughly the experiment.

4.    All the glassware used should be thoroughly cleaned and dried.

5.    All apparatus and measuring should be very accurately.

6.    Zero minute and achromic point reading should be taken very carefully.

7.    All solutions should be make accurately.

8.    Iodine solution should be freshly prepared.