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Lab report


Aim: The aim of this investigation is to detect the enzyme activity of amylase in saliva.


Enzymes are protein catalysts. This means they are chains of amino acids with a particular shape that allows them to interact with a specific molecule called a substrate to bring about a chemical reaction. When the reaction is complete, the enzyme is unchanged and able to interact with another substrate molecule. Many enzymes are present in your digestive system. Each digestive enzyme breaks down a specific type of macromolecule. For example, pepsin breaks down protein and lactase breaks down lactose, a disaccharide. Digestion begins in your mouth with saliva which contains an enzyme called amylase. Amylase works to break down complex carbohydrates. Through hydrolysis, amylase breaks down the polysaccharide, AKA starch, into the monosaccharide, glucose. In this experiment, Iodine solution will be used to test for the presence of polysaccharides in test tubes.

The basic principle of this iodine test is that when an iodine solution (i.e. aqueous solution of potassium iodide) comes in contact in starch, the solution turns blue black in color. In the presence of iodine, amylose in starch forms a deep blue color.

[pic] [pic]

Amylase ,the enzymeStarch, the substrate

[pic] Maltose (a disaccharide), the product

Hypothesis: In this investigation we will study the effect of the enzyme salivary amylase on starch. Salivary amylase is an enzyme that catalyzes the reaction that break starch down into maltose, which is a disaccharide. Iodine will react with the coiled molecules and turn deep blue when added to a solution. A solution that remains a yellowish-brown color is a negative test for starch, whereas one that turns deep blue is a positive test for starch.

In this experiment we will use two kinds of amylase: microbial(Termamyl)l and salivary


24 hole plate

jar of starch

a tube of amylase Termamyl (Group A) / water (group C) / Group B will need


2 Pasteur pipettes

Mixing stick

cup with a prepared solution of iodine

cup of water to rinse pipette


1. Prepare a watch, preferably with a stopwatch function.

2. Add a Pasteur pipette with 1 ml of iodine solution to all wells of the plate with 24 holes.

3. To  the first hole with a clean Pasteur pipette, add one drop of starch, stir. Observe the color of the mixture.

4. Group A: Add to starch 3 ml of enzyme solution Termamyl

5. Thoroughly mix the starch with the enzyme and immediately add one drop to another hole. Start the stopwatch or note the exact time.

Group B: Add to the starch a few milliliters of saliva (volume about 1 teaspoon)

6. After one minute take a sample of starch and add one drop to the third hole, stirring its contents with the pipette tip. Stir starch all the time.

7. Action described in paragraph. 6 repeat every minute, each time noting table color change in the hole and the consistency of starch. It is recommended to rinse the clean water after each collecting pipettes starch, because it would be starch may affect the credibility of the result.

8. You can complete the experience, when a solution of iodine will stop changing color.

Data Collection & Processing

Table 1.1 Iodine test for presence of starch Group A

|No. of hole |Time [min] |Color of the solution | |1 |control |deep blue | |2 |0 |deep blue | |3 |1...
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