Enzymes
Chemical Reactions
Characteristics
of Enzymes (Catalysts)
Speed up
reactions!!!!!!!
!!
Made by the
cells of
organisms
Work in
chemical
reactions.
Are specific
for their job!
Only work
for a short
time.
Do not change in a
chemical reaction!
Enzymes are
used over &
over & over
again (reused)!
** Most enzymes are made of proteins.
But, causes
others to
change in a
reaction.
Lock & Key Model
(Active Site)
KEY IDEA
Enzymes Have A SPECIFIC SHAPE.
This allows them to have SPECIFIC
FUNCTIONS!!!!!!!!!!!!!!!!!!!!!!!!
Lock & Key Model
Substrate
Active
Site
Substrate – the reactant that
binds with the enzyme.
Active Site – the part of the
Enzyme – special proteins that
speed up a reaction. Also, called a
catalyst.
Enzyme-Substrate
Complex – when the
molecule where the substrate fits into
the enzyme.
substrate binds to the enzyme.
Enzymes
Enzymes act like a scissor (break down particle).
Functions of Enzymes (Catalysts)
1. Digestion - break down food
2. Synthesis- build up
More Key Ideas
• Enzymes are also called catalysts.
• Enzymes end in –ase.
• Enzymes are organic molecules made of
proteins.
• Enzymes are written above the arrow
for equations.
Catalase
(enzyme)
Reactants
(combined)
Products
(formed)
Why is the SHAPE of
ENZYMES Important?
An enzymes SHAPE determines
its specific FUNCTION.
If the shape is incorrect, the
enzyme will NOT work or the
reaction will SLOW down or
STOP!!!!!
SHAPE =
SPECIFIC FUNCTION
ENZYMES ARE VERY SPECIFIC AND
ONLY WORK WITH CERTAIN
SUBSTRATES
Enzymes end in –ASE
Examples:
Maltase – breaks maltose into 2 glucose
molecules.
Lipase – breaks down fat
Sucrase– breaks down sucrose into 2 simple
sugars
Lactase– breaks down the sugar in milk into 2
simple sugars
Protease – breaks down peptide bonds in
proteins
Lock and Key
Glucose
Fructose
Sucrose
Dehydration Synthesis or Hydrolysis?
Hydrolysis
____________________
Do Now
1. An example of
synthesis or digestion?
2. An
example of
synthesis or
digestion?
Factors that Affect
Enzyme Reactions
1. Enzyme Concentration
2. Temperature
3. pH
**least affected by light & CO2**
Enzyme Concentration
• More enzymes =
faster rate of
reaction.
• Eventually rate
stops going faster
because there is no
more extra
enzymes.
Enzyme Concentration
• When all substrates
are used up, the rate
is limited because no
more enzymes to
bind with.
• Small amount of
enzymes limit the
reaction rate.
• At the optimum (best)
temp, enzymes function at
the highest rate (faster).
• Optimum temp 98.6° F (36 C)
(human enzymes).
•Reaction rate speeds up till it
reaches its’ optimum rate then
slows down, shape changes, &
breaks apart.
• Active site shape changes = No
enzyme function
(DENATURATION)
Temperature
• Changing pH, changes
the H-bonds and the shape
changes!
pH
• When shape changes
then enzyme action
stops (denaturation)!
• Stomach enzyme (pepsin)
works best at 2-3 pH.
• Small intestine enzymes
work best at a pH of 8.
Optimum pH for
most enzymes