Question

Chemical Digestion of Food - The Role of Enzymes

Experiment Inventory. .

Materials Labware

4 inches Parafilm (4) Test Tubes, Test Tube Rack, 10 mL Graduated Cylinder , (2) Pipettes Note: You must provide the materials listed in *red.

4 mL 1% Iodine-Potassium Iodide (IKI)

*Saltine Cracker

*Stopwatch/Timer

*Water

*Saliva Sample

EXPERIMENT 4: CHEMICAL DIGESTION OF FOOD - THE ROLE OF ENZYMES Enzymes play a key role in the digestion of food. They chemically decompose large molecules into smaller molecules that a body can readily use. This process begins in the mouth, where amylase in saliva catalyzes the conversion of starches into simple sugars. In this experiment, you will use your own saliva to monitor the effect of enzymes on a saltine cracker. As you may know, IKI solution is an indicator that turns dark black-purple in the presence of starch. This will be used to determine the efficacy of the enzyme on the substrate.

PROCEDURE

1. Use the permanent marker to label four test tubes as 1, 2, 3, and 4.

2. Deposit at least 6 mL of saliva into the 10 mL graduated cylinder.

3. Open the saltine pouch. Divide the cracker into approximately equal quarters.

4. Take one-quarter of one cracker and break it into three equally sized pieces. Place into Test Tube 1. Note: You may wish to use a butter knife to gently apply pressure to break the quarter-piece into three smaller pieces. Small crumbling is okay, but be sure to collect the crumbs so that the total mass of each piece is approximately the same.

5. Take a second quarter of the cracker and gently crush it into crumbs. Place the crumbs into Test Tube 2.

6. Repeat step 5 with the third quarter of the cracker and place the crumbs into Test Tube 3.

7. Take the fourth quarter of the cracker and chew it in your mouth for 15 seconds. DO NOT SWALLOW THE CRACKER! Spit the masticated cracker into Test Tube 4.

8. Using one pipette, drop 2 mL of the saliva you collected into Test Tubes 1, 2, and 4. Do not pipette the saliva into Test Tube 3.

9. Rinse the 10 mL graduated cylinder, and fill it with approximately 2 – 3 mL of water. Then, use a new pipette to transfer 2 mL of the water into Test Tube 3.

10.Cover each test tube with Parafilm®.

11. Shake all of the test tubes for 30 seconds. Try to shake all of the test tubes within a 2 minute time interval.

12.Record the initial color of each solution in Table 2.

13.Wait 10 minutes, then add 1 mL of IKI solution to each test tube.

14.Shake the test tubes for another 30 seconds, and note the color of each tube in Table 2.

Experiment 4 Data Sheet

Table 2: Color Observation

Test tube	Initial Color	Final color
1
2
3
4

Answer 1

Test tube	Canker	Saliva	Water	Initial Colour	Final Colour
1	Dry canker	2 ml	0 ml	Dull	Yellow brown	Starch get digested into monosaccharides due to amylase
2	Crushed canker	2 ml	0 ml	Dull white	Yellow brown	Starch get digested into monosaccharides due to amylase
3	Crumbed canker	0 ml	2 ml	Suspended white	Blue black	The absecce of amylase resulted in no digestion of starch due to which blue black colour produced
4	Chewed canker	2 ml	0 ml	Creamson	Yellow brown	Starch get digested into monosaccharides due to amylase