Name:
Living Environment R
Per:
Date:
Lab: How Do Enzymes Work?
Part 1: Modeling Enzyme Activity
A catalyst is any substance that increases the rate of a chemical reaction. Enzymes are specialized protein
catalysts that control metabolic activities like hydrolysis (digestion), synthesis, cellular respiration and
photosynthesis. Enzymes have specific shapes which allow them to bind to the reactants of a particular
chemical reaction. These reactants are known as substrates. The temporary physical connection between the
enzyme and the substrate lowers the activation energy of the reaction, allowing it to occur at a higher rate. The
product will then be released and the enzyme will go on to catalyze more of these reactions.
In this activity, you will choose two compound words. Like a macromolecule, a compound word is made by
combining subunits. For example, ladybug is a word that consists of the subunits lady and bug.
You will design one poster that shows an enzyme synthesizing a compound word and another poster that shows
an enzyme digesting a different compound word. The first poster you will label Synthesis, the second you will
label Digestion. Each poster will have three parts, separated by arrows. The first part will show the substrate(s)
and enzyme separately. The second part will show the substrate(s) and enzyme bound together. The third part
will show the product(s) and enzyme separately. Label all of your substrates, enzymes and products.
Substrates
(lady + bug)
SYNTHESIS
enzyme
Substrate
(ladybug)
enzyme
Product
(ladybug)
enzyme
DIGESTION
Products
(lady + bug)
enzyme
Record your poster design below:
a. Name the compound word that you plan on synthesizing: ___________________________
b. Write out the chemical reaction: _____________________________________________________________
c. Name the compound word that you plan on digesting: __________________________
d. Write out the chemical reaction: _____________________________________________________________
e. Create your posters.
Part 2: Investigating the Enzyme Catalase
Metabolic activities of the cell often produce waste products that are toxic, like hydrogen peroxide (H2O2).
a. How does the cell avoid being poisoned by these waste products? __________________________________
__________________________________________________________________________________________
__________________________________________________________________________________________
b. Write out the chemical reaction that is sped up by catalase: ________________________________________
c. Prepare a sample of potato and a sample of apple.
d. Add a small amount of hydrogen peroxide to the potato sample. Do the same to the apple sample.
e. Record your observations below
Potato Sample
Apple Sample
f. In which sample was catalase present? How do you know? ________________________________________
_________________________________________________________________________________________
g. In the sample with catalase, identify what gas (bubbles) and liquid were produced:
Gas = _______________________
Liquid = ________________________
h. Prepare two more samples of potato.
i. Begin heating one potato sample in the water bath.
j. Make a prediction: How will heating the potato sample change its reaction to hydrogen peroxide? _________
_________________________________________________________________________________________
k. Make a prediction: How will adding an acidic solution to the potato sample change its reaction to hydrogen
peroxide? _________________________________________________________________________________
__________________________________________________________________________________________
l. Add a small amount of acid to your hydrogen peroxide. Use pH paper to record the pH: _________________
m. Add the acidic hydrogen peroxide solution to your potato sample.
n. Remove the potato sample from the water bath. Add hydrogen peroxide.
o. Record your observations below:
Acidic Potato Sample
Heated Potato Sample
Conclusion
1. Explain the effect that changing the pH had on Catalase activity: ___________________________________
__________________________________________________________________________________________
__________________________________________________________________________________________
2. Explain the effect that changing the temperature had on Catalase activity: ____________________________
__________________________________________________________________________________________
__________________________________________________________________________________________
3. Label the diagram below with the following terms: enzyme, substrate, active site, products