Name:___________________________________
Date:_______________
Pd:_____
All About Enzymes
Directions- Read through this worksheet about enzymes. Be sure to answer ALL questions.
Enzyme- a specialized protein that helps speed up chemical reactions in living tissue (acts as a catalyst).
The most common types of reaction that enzymes work on are synthesis (making something big) and
decomposition (breaking down something big). Always remember, if a substance’s name ends in –ase,
they are enzymes (ie: catalase, amylase, protease, etc.)
Substrate- the specific-shaped molecule on which enzymes act. The combination of enzyme and
substrate is known as the enzyme-substrate complex. The spot on an enzyme that the substrate
attaches to is known as the active site.
Question 1.
In the diagram to the left, an
enzyme pairs up with a
substrate, forming an
enzyme-substrate complex.
The enzyme then acts on the
substrate, breaking it
into its two parts. What kind
of reaction is this?
An example of this type reaction is the decomposition of hydrogen peroxide.
Question 2.
What is the formula for that reaction?
Question 3.
In the space below, draw the substrate(s), enzyme-substrate complex and products of an enzymecatalyzed synthesis reaction. I’ve given you the enzyme to start with.
©2010 Brian Nagy, Cairo-Durham High School
Like all proteins, enzymes are very temperamental. If they are not in the perfect (optimum) temperature
or pH (a measure of acidity) zone, they break down or change shape, a process known as denaturing.
This optimum zone is different for each enzyme and from species to species and it depends on the
environment the species lives in. The optimum conditions for bacteria in a hydrothermal vent are going
to be different from those of a spider in the Amazon.
Question 4. What is the word that is used when a protein has broken down because of temperature or
pH?
Below, the left molecule is what an enzyme looks like normally. The molecule on the right is its substrate.
The other diagram shows the same enzyme after heating to a temperature that is not in its tolerance
range. The protein has changed shape.
Normal:
After heating:
Question 5.
Why won’t this enzyme work with its substrate after being heated to high temperatures?
You can find out the optimum temperature and pH of each enzyme by making a graph of enzyme activity.
For our purposes, “Rate of Reaction” and “Enzyme Activity” mean the same thing, which is how well the
enzyme is doing its job.
Above are examples of graphs that show the optimum temperature and pH of an enzyme.
Question 6.
What is the optimum temperature for this particular enzyme? What happens to the enzyme above this
temperature that makes the activity drop so much?
©2010 Brian Nagy, Cairo-Durham High School
Question 7.
What is the optimum pH of the enzyme whose activity is shown on the previous page? How can you
tell?
The human body averages a temperature of 37oC in an adult. The average pH in the stomach is 1.5. The
average pH of the blood is 7.4. The average pH of the small intestine is 7.9.
Question 8.
Will the enzyme whose activity is graphed on the previous page be at its optimum temperature in a
human? If so, where do you think the enzyme is found?
Question 9.
What would you expect the optimum pH of an enzyme in your stomach (like one called pepsin) would
be?
Question 10.
What is a reason that a prolonged period of high fever in our body can cause death?
Question 11.
Up until the optimum temperature the rate of reaction increases as temperature increases. Why is this?
(Hint: it’s the same reason that diffusion goes faster when temperature increases)
Imagine you have a beaker full of a substrate. It might look like this:
Now add an enzyme molecule:
This one molecule has a lot to do, so it will go slowly. The graph below assumes that you have a nearly
unlimited supply of substrates.
Question 11.
©2010 Brian Nagy, Cairo-Durham High School
Assuming that there is a nearly unlimited supply of substrates, what happens to the rate of reaction of
an enzyme-catalyzed reaction if you continue to add enzymes (increase enzyme concentration)?
Now change your beaker. You just have a lot of enzyme.
If you add a single substrate molecule, it will quickly join with the enzyme and the reaction will be done.
As you continue to add more substrate, the rate of reaction graph begins to look like this:
Question 12.
At the point of saturation, the reaction can’t go any faster.
Why? (Remember that there is a fixed number of enzyme
molecules, and increasing amounts of substrate)
Question 13.
In a minimum of 2-3 sentences, describe the job of enzymes. Be sure to discuss at least 2 conditions
that can affect how well enzymes operate.
©2010 Brian Nagy, Cairo-Durham High School
Name:________________
Date:____________________
Environmental Effects on Enzyme Activity
Per: _____________________
Background:
Hydrogen peroxide (H2O2) is the product of many biological reactions, but it is toxic and extra
buildup of peroxide is deadly. Hydrogen peroxide turns into H2O and O2. The breakdown of peroxide
occurs naturally, but far too slow to be of any use to organisms.
The formula for the chemical reaction is:
H2O2  H2O + O2(g)
An enzyme—known as Catalase—greatly speeds up the reaction. Catalase is found in animal
muscle, liver tissue and in the roots of plants.
In this activity, you will be able to compare the relative amounts of catalase in muscle (chicken
breast meat) and a root (potato). You will also see the effect of several different conditions on the
activity of catalase.
Prelab Question:
What does hydrogen peroxide look like? Can you observe it breaking down? Explain.
Safety:
In this activity, you will be handling raw chicken, an acid and a base. It is
recommended that you wear gloves at all times. Splash-resistant goggles should be worn during
this activity, especially while heating water. Care should be taken while using a hot-plate.
Materials:
 5 cubes of raw chicken
 Hydrogen Peroxide (30% if
breast, roughly 3cm per
possible, but 3% will also work)
side, then crushed/chopped
 1 cube raw potato, roughly 3  1 Hot Plate
cm per side, then
 1M Hydrochloric Acid
crushed/chopped
 1M Sodium Hydroxide
 6 250-mL beakers
 1 Ice Bath
 1 tongue depressor
 1 50-mL graduated cylinder
 pHydrion paper
 1 thermometer
Procedure:
1. Label 6 250-mL beakers as follows: Control Chicken, Potato, Boiled Chicken, Chilled Chicken, Acid
Chicken, Base Chicken
2. Place a piece of chicken in the “Boiled Chicken” beaker along with 150 mL water. Put on a
hotplate and place on high heat. Boil until the chicken turns white.
3. Place a piece of chicken in the “Chilled Chicken” along with 150 mL water. Put in the ice bath.
4. Place a piece of chicken into the “Acid Chicken” beaker and carefully pour 20 mL 1M Hydrochloric
Acid over it. Swirl gently and allow to stand.
5. Place a piece of chicken in the “Base Chicken” beaker and carefully pour 20 mL 1M Sodium
Hydroxide over it. Swirl gently and allow to stand.
©2010 Brian Nagy, Cairo-Durham High School
6. 30 mL Hydrogen Peroxide over the “Control Chicken”. Write observations in the data table.
7. Pour 30 mL Hydrogen Peroxide over the potato. Write observations in the data table.
8. Using a thermometer, record the temperature of the water in the “Boiled Chicken” beaker in the
data table.
9. Carefully pour off the water from the boiled chicken. Pour 30 mL Hydrogen Peroxide over the
chicken and record your observations.
10. Using a thermometer, record the temperature of the water in the “Chilled Chicken” beaker in the
data table.
11. Pour off the water from the boiled chicken. Pour 30 mL Hydrogen Peroxide over the chicken and
record your observations.
12. Pour 30 mL Hydrogen Peroxide into the “Acid Chicken” beaker. Observe and record your
observations in the data table.
13. Pour 30 mL Hydrogen Peroxide into the “Base Chicken” beaker. Observe and record your
observations in the data table.
Data Table:
Beaker
Relative Reaction Rate (How
Other Observations
many bubbles do you see?)
Temp:
Potato
pH:
Temp:
Chicken (control)
pH:
Water Temp:
Chicken (ice bath)
Chicken (boiled)
Chicken (acid added)
Chicken (base added)
Water Temp:
pH:
pH:
Analysis Questions:
1. What were you able to observe that shows that the breakdown of peroxide is occurring?
2. Which has more catalase, chicken muscle or potato? How can you tell?
3. Why was the chicken and potato pulverized? (Think about where the catalase is found)
4. Under what conditions of temperature and pH does catalase work best? Justify your response
from evidence.
©2010 Brian Nagy, Cairo-Durham High School