Transcript Enzymes! - Mrs. Ahrens` Science Site

Enzymes!
(What are they good for?)
Essential Questions:
What is an Enzyme?
How do they work?
What are the properties of Enzymes?
How do they maintain Homeostasis for the body?
What are Enzymes?
• Enzymes are proteins which act as biological
catalysts.
– A catalyst is a substance that starts or speeds up a
chemical reaction without itself being affected.
– It lowers the activation energy required for the
reaction to take place.
• Their subunits are amino acids.
• Enzymes are used by cells to trigger and control
chemical reactions.
• Without enzymes, several reactions in cells would
never occur or happen too slowly to be useful.
Wait, What is a Chemical Reaction?
• It is the process of changing one set of
chemicals (reactants) into another set of
chemicals (products) by rearranging the
atoms.
• Reactants’ bonds are broken and new ones
are formed in the products.
2H2 + O2 → 2H2O
Wait, What is activation energy?
• Activation
energy is the
amount of
energy needed
to start a
chemical
reaction.
Ok, so How do Enzymes Work?
• Enzymes enable molecules called
reactants to undergo a chemical reaction
with specific substrates and form new
substances called products.
• Energy can be exothermic (release heat,
energy) or endothermic (require heat,
energy)
• Enzymes speed up chemical reactions
that take place in cells.
– They lower activation energy
• They catalyze specific
substrates into products
and leave the enzyme
unchanged and ready to
catalyze the next reaction.
What is a substrate?
• Enzymes bind to molecules called substrate(s).
• The(se) substrate(s) are the reactants that are
catalyzed by the enzyme.
– Example: Typically something we ingest that needs
to be broken down further for use by the body like
Lactose from Cow’s milk. (Done by Lactase)
Enzyme Animation:
http://www.youtube.c
om/watch?v=V4OPO6
JQLOE
Enzyme Action: Locks & Keys
• Enzymes provide an area where
reactants can be brought together
to react.
• The site on the enzyme where the
substrates bind is called the active
site.
• The reactants are called the
substrate(s).
• The substrate(s) enters the active
site which becomes the enzymesubstrate complex.
• The shape of an enzyme is so
specific that generally only one
enzyme will work for one
substrate(s).
The fit is so exact
that the active site
and substrates are
compared to a
“lock and key”.
http://www.youtube.com/watch?v=V4OPO6JQLOE
Enzymes: Catch & Release
• After the enzyme has complexed
with the substrate, the change
molecule is released (called a
product) to be used by the body.
• Each protein has a specific shape,
therefore enzymes bind to
substrates based on shape.
– the substrates are based on the
complementary shape of their
specific enzyme.
Recall: Based upon what
you know about proteins,
what is it about enzymes
• Since only the substrate changes
that allows them to be so
during the reaction, the enzyme
specific to only one
can be reused again and again.
substrate?
Because of the different combination of the 20 essential amino acids, there are
thousands!
http://en.wikipedia.org/wiki/List_of_enzymes
Induce Fit Hypothesis
• Enzymes can change shape slightly to fit
the substrate a little better (like a hand in
glove).
Induced Fit Animation:
http://www.youtube.com/watch?v=ybahzSjUpB0&feature=PlayList&p=C846C10E855
E64E1&index=12&playnext=2&playnext_from=PL
Enzymes can be turned on and off.
• Enzymes work best at specific temperatures and pH.
• Heating and the wrong pH can change the enzyme shape
affecting the binding of the substrate to the enzyme.
– Recall: What is the term for heating of enzymes called? denature
• Ergo, enzymes in our body work best at 37°C (98.6°F)
and at a pH between 6.5 to 7.5.
• Also, most cells contain proteins that turn enzymes on or
off during critical stages of development.
What other
factors
control this
enzyme?
Co factors
l, r, and x
Enzyme Characteristics: Review
• Remember, Enzymes are catalytic
proteins.
1. Speed up reaction rate but do not
change the reaction.
2. Enzymes are very specific.
3. Enzymes work like locks & keys.
– Example: Lactose and Lactase
4. Enzymes are unchanged.
5. Enzymes are sensitive to changes in
temperature and pH.
6. The suffix –ase means it is an enzyme.
– Example: lactase, sucrase
cellulase, maltase…