Background

Starch digestion begins in the mouth due to the amylase enzyme present in saliva. Salivary amylase converts the polysaccharide starch into many disasccharide molecules of maltose (a simple sugar) which are further broken down into glucose units by maltase enzyme in the intestine. The efficiency of starch digestion by amylase can be measured by how much simple sugar it produces under various conditions.

Materials and Methods

Prepare 4 clean, dry test tubes in a stand and label them #1-4 with masking tape.

1. Fill test tube #1 half full with water only.


2. Carefully spit into test tube #2 until it is about one-quarter full with saliva. Add water to bring the level up to half full.


3. Carefully spit into test tube #3 until it is about one-quarter full with saliva. Add water to bring the level up to half full. Add ____ mL of concentrated acid to test tube #3 and let stand for 10 minutes.


4. Carefully spit into test tube #4 until it is about one-quarter full with saliva. Add water to bring the level up to half full. Place test tube #4 in a very HOT water bath and heat while stiring the bath for 10 minutes. Then remove from bath.


5. Crush up a cracker and place an equal amount of the product in each of the 4 test tubes. Mix the cracker with the saliva thoroughly. Let the test tubes stand for 15 minutes.


6. Add 10 drops of Benedict's solution to each test tube and place them in a WARM water bath for about 5 minutes. Then complete the Observations Table.


7. Thoroughly clean and dry all equipment.

Questions (answer fully on note paper)

1. What was the purpose of test tube #1?


2. a) At what pH does amylase work in the body to perform starch digestion?
   b) What effect did adding acid to test tube #3 have on amylase?
   c) Was there more or less starch breakdown in the tube?
   d) Was there more or less maltose produced?


3. a) At what temperature does amylase work in the body to perform starch digestion?
   b) What effect did heating test tube #4 in the very HOT water bath have on amylase?
   c) Was there more or less starch breakdown in the tube?
   d) Was there more or less maltose produced?


4. a) Describe the appearance of test tube #2 and #3 if you used iodine solution instead of Benedict's solution.
   b) Explain what the iodine test is telling you about each tube.


5. Do all enzymes work best at neutral pH? Discuss citing examples.


6. "Heartburn (acid indigestion) occurs when stomach acid moves up into the esophagus, burning its lining. Antacids can be taken to neutralize the acid and reduce the burning."
   

   Explain why using too many antacids can lead to a reduced ability to digest protein?