Structure-function relationship in salivary α-amylase
Introduction:
Amylase is an enzyme that facilitates the decomposition of starch into glucose. We will test the
idea that structure and function re interdependent using thisi enzyme.
Enzymes are proteins. Proteins can be denatured in low pH or at high temperatures. We will test
the enzyme’s ability to carry out its biological function after exposure to these environmental
factors.
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Describe the chemical structure and biological function of enzymes.
Enzymes make it possible for chemical reactions to proceed by lowering the activation
energy – they reduce or eliminate the need for a large addition of energy to get the
chemical reaction started. Explain why this is important in a cell.
Apply the concept of the structure-function relationship to the of enzyme-substrate
specificity.
What does it mean for a protein to be denatured?
If structure and function are interdependent, what should happen to the enzyme’s
function when denatured by heat or low pH? Why?
Methods:
Collect and dilute a sample of saliva. Divide the sample into three equal parts. To one part, add
25% of the part’s volume of 2.0M HCl(aq). To the second part, add the same amount of distilled
water and place in a boiling water bath. To the third part, add the same amount of distilled water –
this will be the undenatured “good” enzyme. This third prep should show us the typical function of
the intact enzyme with its substrate. We will include a fourth preparation without any of the
enzyme sample, just distilled water.
To each of these four preps, add an equal volume of dilute starch solution. Allow the experimental
setup to sit for 15 minutes. This should allow enzymatic activity to occur.
Test for the presence of starch using iodine indicator. Iodine turns purple or black in the presence
of starch.
Results:
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Prepare a table to report the outcome of the tests for starch.
Discussion:
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Describe trends, patterns, and events in your observations. Which tests were positive,
which negative?
Identify the cause and significance of positive and negative tests for starch.
Apply the concept of structure-function interdependence to your observations.