ENZYMES and METABOLIC REACTIONS
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Transcript ENZYMES and METABOLIC REACTIONS
ENZYMES and
METABOLIC
REACTIONS
ENZYMES and METABOLIC
REACTIONS
How
do reactions occur in cells?
Molecules are in constant motion
Collisions between molecules allow
reactions to occur
ENZYMES and METABOLIC
REACTIONS
Enzymes
Are protein catalysts that allow chemical
reactions to take place in our body without
increasing the temperature
Usually end with the suffix ‘-ase’
Examples: urease, amylase, sucrase
Catalysts
Control
the speed of reactions without
changing the products formed
They do this by reducing the activation
energy
Enzymes…
Work
on molecules called the substrate
Can be anything
Enzymes…
Work
on molecules called the substrate
Can be anything
Are
substrate-specific
Enzymes…
Work
on molecules called the substrate
Can be anything
Are
substrate-specific
Alter the substrate in some way
Substrate
approaches an
enzyme
The enzymesubstrate
complex is
formed
Reaction is complete.
Enzyme remains
unchanged.
Products are formed.
Enzymes Models
Where
the substrate
joins the enzyme is
called the active
site
‘Lock and Key
Model’
The
active site of an
enzyme is a perfect
match to a specific
substrate
Enzymes Models
‘Induced-Fit
Model’
The
active site
changes shape
slightly when the
E-S complex join
together
Makes a tighter fit
Factors that Affect Enzymes
1. Temperature
Reaction
rates increase
as temperature
increases
Peaks at ~ 37 - 40°C
then drops rapidly
Why?
E.g.
egg frying
What
happens at
cooler temperatures?
Factors that Affect Enzymes
2. pH
Enzymes
function within an optimal pH range
Stomach
pH
Small intestine pH
Factors that Affect Enzymes
3. Concentration of Substrate Molecules
Reaction rate increases as the substrate
concentration increases up to a point
The limiting factor in the reaction may be
the amount of substrate or the amount of
enzyme available
4. Inhibitor molecules
Molecules that attach to the enzyme
and reduce its ability to bind substrate
There are two types of inhibitors
Competitive inhibitors
Non-competitive inhibitors
4. Inhibitor molecules
a. Competitive inhibitors
•
•
•
Attach to enzyme’s active site
Shape is similar to substrate
Compete with the substrate
E.g. drugs and
poisons
- CO
- Cyanide
4. Inhibitor molecules
b. Non-competitive inhibitors
•
•
•
Attach elsewhere on the enzyme (not the active site)
Attachment changes the 3D shape of enzyme
Reaction still occurs, but is inhibited