1. BIOLOGY
102
ENZYMES
SB1.b. Explain how enzymes function as
catalysts.

2. What is an enzyme?
 Also called a
biological catalyst
 Protein that speeds
up the rate of a
reaction.
 Not changed during
the reaction.
 Used over and over
until the reactant is
used up.

3. Why are enzymes important?
Green line is reaction without enzyme
 Decreases the amount Red line is reaction WITH enzyme.
of energy needed
(activation energy) for a
reaction to occur.
 As a result, the reaction
happens faster.

4. What would happen if we did not
have enzymes or they did not
work properly?
 You would DIE!
 No enzymes =
reactions happening
too slowly so body
can’t get what it
needs to survive.

5. How does an Enzyme Work?
 Each enzyme has a
specific shape which
causes it to bind with
specific reactants
Parts of an Enzyme-
Substrate Complex:
 Substrates- reactants that fit with
enzyme
 Active site- site on enzyme that
substrates bind to
 Products- created from
combining of substrates. This is
what leaves the enzyme

6. How Does an Enzyme Work?
 Because only SPECIFIC substrates will
fit in SPECIFIC enzymes they are often
compared to a LOCK & KEY MODEL

7. How Does an Enzyme Work?
 Enzymes work one of two
ways Two reactants bind together
to make one product
– Bind two reactants to make
one product (see picture on
right)
– Break bonds in large
molecule to make many
smaller ones (see picture
below)
One reactant is broken apart to make two products. Orange structure is enzyme,
green & blue parts in first part of picture are substrates.

8. What may alter enzyme
functioning?
 pH, salt concentration,
temperature
 All will DENATURE enzyme.
 Changes its shape so it no
longer accepts substrates so
can’t create products.
 This would slow down/stop
reactions from happening in
body.
 Great Website to show Enzyme activity

9. Can you answer these questions about the
picture below? (Check answers on next
page.)
1. What type of macromolecule is an enzyme?
2. What is another name for enzyme?
3. What is the enzyme term for #2?
4. What is the enzyme term for the site on the enzyme where the sucrose attaches?
5. What is added at #3?
6. What is the enzyme term for the glucose & fructose created at #4?
7. Has the enzyme changed in this reaction?
8. What types of factors could denature the enzyme?
9. What will happen if the enzyme is denatured?

10. Can you answer these questions about the
picture below? ANSWERS
1. What type of macromolecule is an enzyme? Protein
2. What is another name for enzyme? Catalyst
3. What is the enzyme term for #2? Reactant or substrate
4. What is the enzyme term for the site on the enzyme where the sucrose attaches?
Active Site
5. What is added at #3? Water (H2O)
6. What is the enzyme term for the glucose & fructose created at #4? Products
7. Has the enzyme changed in this reaction? No- has same shape so can be
reused
8. What types of factors could denature the enzyme? pH, temperature, salt
9. What will happen if the enzyme is denatured? Active site is changed so reactants can no
longer fit into enzyme so reaction can’t happen. This means you can no longer break down sucrose
to get the glucose & fructose so cells can’t absorb these glucose & fructose molecules to use them.
Cell may “starve” for these molecules.

11. Can you answer these questions about the
graph below? (Check answers on next page.)
This graphs shows how an enzyme
functions at different pH levels.
1. This enzyme works best at
which pH?
2. Would you find this enzyme
in your stomach or blood?
How do you know?
3. What would happen to the
amount of product made if
the pH rose to 13?

12. Can you answer these questions about the
graph below? ANSWERS
This graphs shows how an enzyme functions
at different pH levels.
1. This enzyme works best at which pH? pH 7
2. Would you find this enzyme in your stomach
or blood? Blood How do you know?
Stomach has acidic environment so would
need an enzyme that works best at an
acidic pH level.
3. What would happen to the amount
of product made if the pH rose to
13? The amount of product
would decrease b/c the enzyme
does not work well at that pH.

13. 1. Enzymes are compared to a lock & key because
a. They open up cells and let stuff in
b. They have very specific active sites so can only participate in a specific
reaction
c. They destroy specific enzymes
2. The structure labeled biological catalyst is
a. a substrate
b. an Enzyme
c. a ribosome
3. How does a lower temperature (refrigeration) affect the rate of enzyme activity?
a. It speeds it up b. It slows it down c. It has no effect
1. During the canning process, heat is used to destroy bacteria in food. How does this
affect enzymes?
a. They are not affected b. They are denatured c. They multiply
1. What is the optimum pH for this enzyme?
a. 3 b. 7 c. 14
6. Will this enzyme function any differently at a pH of 16?
a. Yes b. no