Enzymes
1
Apple Experiment
Come and get 2 slices of apples ( A & B – keep
separate), paper towel and a bottle of lemon
juice.
When you get back to your seat:
1. Write A & B on paper towel. Place apple A on A side and apple B on B side
2. Immediately squeeze lemon juice over apple slice B.
3. IMPORTANT! Don’t get lemon juice all over both slices.
4. Set your apple slices aside and return the lemon juice bottle.
From the Virtual Cell Biology Classroom on ScienceProfOnline.com
What are
enzymes?
• Enzymes are
Proteins
(tertiary and
quaternary
structures).
From the Virtual Cell Biology Classroom on ScienceProfOnline.com
Image: Levels of protein structure, M Ruiz
Why Are Enzymes So Important?
Why are we devoting
one whole lecture topic
to a protein molecule?
Nearly all chemical
reactions in
biological cells need
enzymes to make
the reaction occur
fast enough to
support life.
From the Virtual Cell Biology Classroom on ScienceProfOnline.com
Image: Jumping rope, Meagan E. Klein
What Are Enzymes?
• Acts as a Catalyst.
A catalyst speeds up
a chemical reaction.
• Not permanently
changed in the
process
5
Enzymes
• Are specific for
what they will
catalyze
• Are Reusable
• End in –ase
-Sucrase
-Lactase
-Amylase
6
How do enzymes Work?
Enzymes work by
weakening
bonds which
lowers
activation
energy
7
Enzymes
Without Enzyme
With Enzyme
Free
Energy
Free energy of activation
Reactants
Products
Progress of the reaction
8
9
Enzymes…
•
fit with substrate
like a ____ and
____.
From the Virtual Cell Biology Classroom on ScienceProfOnline.com
Enzyme-Substrate Complex
The substance
(reactant) an
enzyme acts on
is the substrate
Substrate
Joins
Enzyme
11
Active Site
• A restricted region of an enzyme
molecule which binds to the substrate.
Active
Site
Substrate
Enzyme
12
• Enzymes can
break apart
substances or
put substances
together.
13
What Affects Enzyme Activity?
• Three factors:
1. Environmental Conditions
2. Cofactors and Coenzymes
3. Enzyme Inhibitors
14
1. Environmental Conditions
1. Extreme Temperature are the most
dangerous
- high temps may denature (unfold)
the enzyme.
2. pH (most like 6 - 8 pH near
neutral)
3. Ionic concentration (salt ions)
15
2. Cofactors and Coenzymes
• Inorganic substances (zinc, iron) and
vitamins are sometimes needed for proper
enzymatic activity.
• Example:
Iron must be present in hemoglobin in order
for it to pick up oxygen.
16
Inhibitors
Competitive inhibitors: are
chemicals that resemble an
enzyme’s normal substrate and
compete with it for the active
site.
Substrate
Competitive inhibitor
Enzyme
17
Meet the Enzyme:
Catecholase
_________ juice and other acids are used to preserve
color in fruit, particularly apples, by lowering the ____
and removing the copper (cofactor) necessary for the
enzyme to function.
Reaction:
catecholase
catechol
colorless substrate
+ O2
----------
Images: Apples, T. Port; Lemons, André Karwath; Enzyme
with Cofactor, Wiki; pH scale, Edward Stevens, Wiki
polyphenol
brown product
From the Virtual Cell Biology Classroom on ScienceProfOnline.com
Look at your apple slices
• Observe and write down
any differences in slices.
• Do you think the lemon
juice had an effect on
apple?
• What do you think
happened? Please
explain.
19
Confused?
Here are some links to fun resources that further
explain enzymes:
•
Enzymes Main Page on the Virtual Cell Biology Classroom of
•
“How Enzymes Work”
•
Interactive Enzyme Tutorial and quiz from Life: The Science
•
“The Role Enzymes Play in the Body” from Enzymedica.
•
“Assignment Discovery: Enzyme Catalysts” from
•
“Enzymes and Digestion” from About.com.
•
“Bio
•
And why not sing “Goodtimes with
“Goodtimes.” See next slide for lyrics.
Science Prof Online.
an animation from McGraw-Hill.
of Biology.
These guys are selling supplements. I don’t endorse the supplement, but
their video is very instructive regarding enzymes and digestion.
HowStuffWorks, a Discovery Company.
Rad GTCA Song” musical advertisement for SsoFast™.
Enzymes” to the Chic song
(You must be in PPT slideshow view to click on links.)
From the Virtual Cell Biology Classroom on ScienceProfOnline.com