The effect of temperature activity of salivary amylase on starch. By Dev Mandal Chemistry Investigatory Project

1. Chemistry Investigatory
Project
AISSCE 2022-23
Topic:- The effect of
temperature activity of saliva
on starch.
Name : Dev Mandal
Class : XII
Roll no :
Subject and code : Chemistry (043)
Directed by:- Mr. Nishit Kumar Priyadarshi
ODISHA ADARSHA VIDYALAYA
GONDHIPALLY, MALKANGIRI
Pincode:- 764045

2. REFERENCES
1. Chemistry Laboratory Manual of class 12
by NCERT
2. AMRITA Vishwa Vidyapeetham
3.OLABS Education
4. CDAC, Mumbai
5. NCERT at FINGERTIPS (Biology)
class 11 by MTG team.

3. TABLE of CONTENTS
1.Introduction
2.Working of salivary
amylase
3.Effect of Temperature
4.Effect of pH
5.Experiment
5.1 Aim
5.2 Apparatus & Materials
Reqiured
5.3 Theory
5.4 Procedure
5.5 Observations
6. Conclusion

4. Introduction
All living beings need energy to survive. It is
from the food we consume that we get our energy.
We know that the energy we are getting is by
the process of digestion that breaks down the
complex substance of starch into simpler
molecules of glucose, which are further
metabolized into CO2 and water through the
process of glycolysis. The human digestive
tract starts at the mouth and ends at the anus.
Working of Salivary
Amylase
The digestion of the food starts as soon as we
put food in our mouth. Our teeth cut the food
into small pieces and the salivary glands
secrete saliva that mixes with these food
materials. The saliva contains an enzyme called
salivary amylase which hydrolyses starch into
maltose. The saliva secreted into oral cavity
contains electrolytes (Na
+
, K
+
, Cl
-
, HCO3
-
) and
enzymes, salivary amylase and lysozyme The
chemical process of digestion is initiated in

5. Salivary Amylase
pH 6.8
the oral cavity by the hydrolytic action of the
carbohydrate splitting enzyme, the salivary
amylase.
Salivary amylase converts starch into maltose,
isomaltose and small dextrins called '
α' dextrins. About 30 percent of starch in the
food is hydrolysed in the oral cavity. Lysozyme
present in saliva acts as antibacterial agent
that prevents infections.
Starch Maltose + Isomaltose + α-Dextrins
The complete digestion of starch occurs only in
the small intestine by the action of pancreatic
amylase.
The activity of enzymes is strongly affected by
several factors, such as temperature and pH.

6. Effectof Temperature
All enzymes are proteinaceous in nature. At a
lower temperature, the enzyme salivary amylase
is deactivated and at the higher temperature,
the enzyme is denaturated. Therefore, more time
will be taken by an enzyme to digest the starch
at lower and higher temperatures. Optimum
temperature for the enzymatic activity of
salivary amylase ranges from 32 °C to 37 °C.
The optimum temperature means that the
temperature at which the enzyme shows the
maximum activity. At this optimum temperature,
the enzyme is most active and hence, takes less
time to digest the starch.
Effect of pH
The optimum pH for the enzymatic activity of
salivary amylase ranges from 6 to 7. Above and
below this range, the reaction rate reduces as
enzymes get denaturated. The enzyme salivary
amylase is most active at pH 6.8. Our stomach
has high level of acidity which causes the
salivary amylase to denature and change its
shape. So the salivary amylase does not
function once it enters the stomach.

7. Experiment
Aim
In order to study the effect of temperature on
the digestion of starch by saliva
Materials Required
Three series of test tubes having iodine
solution in each, test tubes, ice cubes, water,
15 ml 1% starch solution + 3 ml 1% NaCl, saliva
solution, droppers, thermometer, Bunsen burner
and wire gauze.
Take about 20-30 mL of warm distilled water
(30°C– 40°C) in the mouth and mix it with the
saliva by gargling in the mouth. Collect the
saliva mixed water in a beaker.
Procedure
1. Take 10 mL of the starch solution in a
boiling tube and add 2mL of 1% sodium
chloride solution in it.
2. Keep the boiling tube in a water bath,
maintained at 30° – 40°C, for at least 15
minutes.
3. Pour 2 mL of the saliva solution in the
boiling tube and start the stopwatch

8. immediately.
4. Take out 2-3 drops of the mixture after
one minute and pour it in the test tube
containing iodine solution.
5. Shake the contents of the test tube and
note the colour of the solution, if any.
Similarly, take out 2-3 drops of the
mixture from the boiling tube after every
oneminute and add to iodine solution
contained in the test tubes.
6. Record the colour of the solution in
each case.
7. Stop taking readings when there is no
change in colour.
8. Record the readings in a tabular form.
In order to study the effect of temperature
on the digestion of starch by saliva,
perform the above experiment at 50°C.
9. The effect of pH of reaction medium
can also be studied by using small
quantities of dilute HCl and dilute NaOH in
the separate experiments carried out in the
same manner as above.
Result
The effect of temperature and pH on the
activity of salivary amylase on starch can be
studied by using the Iodine test. If we add
saliva on starch, the salivary amylase present
in saliva gradually acts on starch and converts
it into maltose. Starch keeps on giving blue
colour with iodine till it is completely
digested into maltose. At this point, no blue
colour is formed. This is the end point or

9. achromic point.
It takes less time to reach achromic point at
37°C, as the enzyme is maximum active at this
temperature, while at higher and lower
temperatures more time is taken to reach the
achromic point.
Conclusion
All enzymes are proteinaceous in nature. At
lower temperatures, the enzyme salivary amylase
is deactivated and at higher temperatures, the
enzyme is denaturated. Therefore, more time
will be taken by enzyme to digest the starch at
lower and higher temperatures. At 37° C, the
enzyme is most active, hence, takes less time
to digest the starch.
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