Question: How Do Acids and Bases Affect Enzymes?

Summary: Enzymes are proteins that accelerate chemical reactions. They occur in the body in our digestive system, for example, to speed up the process of breaking down food into molecules that provide nutrients to the body. They are also using in many manufactured products, including cleaning products, cheese, beer, and biofuels. This experiment tests the effect of different levels of acids and bases on a common enzyme—yeast.

Materials Needed:

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5 70 mL Glass Test Tubes 

Plastic Test Tube Rack  

Masking Tape

Permanent Marker Pen

Active Dry Yeast

5 plastic drink stirrers

1 small glass

Distilled Water (1/2 Cup)

Baking Soda

Set of measuring teaspoons

Hydrogen Peroxide

Lemon Juice

Baking Soda

Ruler

Measuring Cup

pH test strips                    

Pen and Paper for Taking Notes

Project Procedure:

1. Label the test tubes as follows: #1-Control, #2-Low Acid, #3-High Acid, #4-Low Base, #5-High Base using the masking tape and permanent marker and place each test tube in the stand.
2. Place one of the drink stirrers in each of the test tubes. Do not move them from one test tube to another.
3. To the test tube marked #1-Control, add 2 teaspoons of distilled water, 1/8 cup (1 oz.) of hydrogen peroxide and 1/8 teaspoon yeast. Use the ruler to measure the highest point that bubbles reach and record that on your note paper.
4. To the test tube marked #2-Low Acid, add one teaspoon of distilled water, one teaspoon lemon juice, 1/8 cup hydrogen peroxide, and 1/8 teaspoon yeast. Stir. Use the ruler to measure the highest point that bubbles reach and record that on your note paper.
5. To the test tube marked #3-High Acid, add two teaspoons of lemon juice, 1/8 cup of hydrogen peroxide and 1/8 teaspoon yeast. Stir. Use the ruler to measure the highest point that bubbles reach and record that on your note paper.
6. Pour ½ C of distilled water into the small glass. Add 1 teaspoon of baking soda, stirring to dissolve.
7. To the test tube marked #4-Low Base, add one teaspoon of the baking soda solution you created. one teaspoon of distilled water, 1/8 cup of hydrogen peroxide, and 1/8 teaspoon of yeast. Stir. Use the ruler to measure the highest point that bubbles reach and record that on your note paper.
8. To the test tube marked #5-High Base, add two teaspoons of the baking soda solution, 1/8 cup of hydrogen peroxide, and 1/8 teaspoon of yeast. Stir. Use the ruler to measure the highest point that bubbles reach and record that on your note paper.
9. Use the pH test strips to measure the pH of each test tube Record this information and use it, along with the measurements of the height of the bubbles, to hypothesize about how acids and bases affect enzyme activity.