Explain where and why salivary amylase would be most active

434

Our aim is to study the effect of different temperatures and pH on the activity of salivary content, amylase on starch.

Theory

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.

In the Beginning

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 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.

Effect of 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.

How to test it?

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 achromic point.

Learning Outcomes:

• Students understand the process of digestion of starch by salivary amylase.
• Students understand the effect of temperature and pH on the activity of salivary amylase on starch.
• Students do the experiment better in the real lab having gone through the animation and simulation.

Papers of particular interest, published recently, have been highlighted as:

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