Download Essential Questions: What is an enzyme? How do enzymes work

Enzymes
Essential Questions:
What is an enzyme?
How do enzymes work?
What are the properties of enzymes?
How do they maintain homeostasis for the body?
What happens to the food we eat?
It gets broken down!
What happens to the food we eat?
Many substances have lactose in it. Why can we
not accept lactose the way it is?
It is too big! Our body
cannot process it.
So we have enzymes to
break it down.
What are Enzymes?
• Enzymes are proteins which act as biological
catalysts.
– A catalyst is a substance
that starts or speeds up
a chemical reaction.
– It lowers the activation
energy required for the
reaction to take place.
• 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.
What are Enzymes?
What enzyme breaks down lactose?
Lactase
What is the function of Lactase?
Lactase breaks lactose into the smaller sugars
glucose and galactose
What are Enzymes?
• Proteins!
• What is the monomer
of an enzyme (or any
protein)?
• What does the function of
an enzyme depend on?
• What do nucleic acids
(DNA) have to do with
enzymes?
Wait, What is a Chemical Reaction?
• The process of changing one set of chemicals
(reactants) into another set of chemicals
(products) by rearranging the atoms.
• The bonds joining the reactants are broken
and new bonds are formed in the products.
• All life processes are driven by chemical
reactions
2H2 + O2 → 2H2O
Wait, What is activation energy?
• Activation energy is the
amount of energy
needed to start a
chemical reaction.
How do Enzymes Work?
• Enzymes catalyze (speed
up) chemical reactions
between reactants
(substrates) that form
new products.
• After the reaction,
enzymes are unchanged
and ready to catalyze the
next reaction.
The Enzyme Catalyzed Reaction
E +
S
ESC
E + P
Enzyme + Substrate yields Enzyme Substrate Complex yields Enzyme + Product
How do enzymes speed up reactions?
• Enzymes lower activation energy
What is a substrate?
• Enzymes bind to molecules called substrate(s).
• The(se) substrate(s) are the reactants in the
chemical reaction that is 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 Activity: 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 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”.
Enzyme Activity: Catch & Release
• After undergoing a
reaction in the enzymesubstrate complex, the
changed substrate is
released as a product to
be used by the body.
• Since only the substrate
changes during the
reaction, the enzyme can
be reused again and again.
The fit is so exact
that the active site
and substrates are
compared to a
“lock and key”.
So many enzymes!
• Recall: Based on what you know about
proteins, what is it about enzymes that allows
each one to be specific to a single substrate?
(ie: how are there so many different enzymes to
fit all of the different substrates in our bodies?)
Because of the different combination
of the 20 essential amino acids!
• Recall: What is it each
amino acids that makes
each one different?
The R-group!
Induce Fit Hypothesis
• Enzymes can change shape slightly to fit
the substrate a little better
(like a hand in a glove).
What factors affect enzyme function?
1. Enzymes work best at specific temperatures and pH.
– Extreme temperature and pH can change the shape of the enzyme,
affecting the binding “active” site.
– Recall: What is the term for destroying an enzymes (or any
protein)?
– Enzymes in our body work best at 37°C (98.6°F) and at a pH
between 6.5 to 7.5.
2. Cells contain proteins that turn enzymes on or off during
critical stages of development.
Enzyme Characteristics: Review
• Enzymes are catalytic proteins.
Enzymes…
1. …speed up reaction rate. They do not change the
reaction.
2. …are very specific.
3. …work like locks & keys.
4. …are unchanged by the reaction.
5. …function depends on structure (shape)
6. …are sensitive to changes in temperature and pH.
The suffix –ase means it is an enzyme.
– Example: lactase, phenolase, sucrase