Download Enzymes (B11)

Enzymes
PLO
B11
It is expected that students will…
analyse the roles of enzymes in
biochemical reactions
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activation energy
activation site
biochemical reaction
coenzyme
competitive inhibitor
denature
endocrine gland
enzyme
enzyme activity
enzyme concentration
heavy metal
homeostasis
homeostatic
mechanism
induced fit model
metabolic rate
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metabolism
negative
feedback
non-competitive
inhibitor
pH
proteins
reactants
substrate
substrate
concentration
thyroid
thyroxin
tissue
tissue fluid
vitamins
How Enzymes work animation
 http://highered.mcgrawhill.com/classware/selfstudy.do?isbn
=0072986751
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(chapter 6 – “How Enzymes Work” (google inquiry into life 12th ed.)
Enzymes are catalyst (a substance that speeds up a
reaction without being consumed).
Enzymes are proteins and are reusable.
They work in low concentrations and speed up the
reaction rate.
Amylase
Starch
Lipase
Lipids
Glucose
Fatty Acids and Glycerol
Protease
Proteins
Amino Acids
Enzymes allow reactions to proceed at lower
temperatures than they would normally occur.
The reactant(s) acted on is known as the substrate(s).
Enzymes work by forming a very temporary complex called
the ENZYME SUBSTRATE COMPLEX.
Enzymes have
grooves (or pockets)
These areas are
called active sites
and this is where the
substrate attaches.
› E + S  ES  E + P
Specific groove shapes in an active site means that
enzymes can only bond with one specific
substrate (reactant)
•When substrate and active site shapes don’t
precisely match, the shape of the enzyme changes,
which makes it more reactive.
http://www.phschool.com/science/biology_pl
ace/labbench/lab2/images/indfit.gif
Many enzymes are made up of 2 pieces: a protein
portion (inactive) & CO-ENZYME, a non-protein
portion
When co-enzyme binds to active site, the enzyme
becomes active and the substrate will now ‘fit’
into the active site.
•
co-enzymes tend to be vitamins (vit B,
riboflavin, niacin, etc).
Co-enzymes usually fit into the ALLOSTERIC site, which
changes the shape of the active site so the substrate can “fit.”
•Definition: Metabolism is
the sum of all the chemical
reactions that occur in a
cell.
•These chemical reactions
occur in organized
sequences from
reactants to end
products with the help of
enzymes.
•This organized sequence
of reactions is known as a
metabolic pathway.
REACTANT
Intermediate
products
PRODUCT
Usually, heat is used to speed up chemical reactions by
increasing the number of collisions that occur between
reactants.
Excessive heat, however,
destroys the tertiary structure
of protein (denatures it).
Therefore, heat cannot be
used to speed up reactions
within living organisms.
Enzymes operate by lowering the energy of activation (EA)
needed for a reaction to occur.
EA = the initial investment of energy to cause a reaction
1.
(lowering EA )
Concentration: more enzyme and/or substrate
means more collisions
The reaction speeds up as the [substrates] increases, and it
levels out when the enzymes are working at the maximum
speed (saturation).
What can you do
to cause an
increase in
reaction rate?
Add enzymes!
The reaction speeds up as you increase the
[enzyme], and slows down as the substrate has all
been turned into product.
What can you do
to cause an
increase in
reaction rate?
Add substrate!
Enzyme Concentration
Temperature:
the reaction rate will increase as the
molecules move faster, increasing collisions
2.
At a certain point, the rate of these collisions will be at the
fastest rate. This is the OPTIMUM TEMPERATURE.
• above
the optimum
temperature, the enzyme
becomes denatured
(changes shape) and no
longer functions properly.
Most of our enzymes have an optimal temperature
of 37oC (body temperature).
 temperature
changes affect enzyme
shape & hence, its activity.
› Below 40C change can be reversed
› Above 40C change is permanent
 in
cold, molecules move slowly so few
collisions
› In cold temp., it gets hard to tie shoes
because enzymes operating slowly –
fingers can’t work
3.
pH:. All enzymes have an optimal pH. Extremes of pH can
alter enzyme shape & therefore, affect enzyme activity.
• Saliva pH 7
• Stomach pH 2.5
• Intestines pH 8.5
• Vagina pH 2.5
4. Inhibitors: Chemicals that interfere with
the enzyme action.
There are two types of INHIBITORS:
a) Competitive Inhibitors
b) Non-Competitive Inhibitors
Allosteric Site
a) Competitive Inhibitors resemble normal
substrate molecule & competes for active site.
Reduces productivity of enzyme by blocking
substrate from entering active site
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In humans, hydrogen cyanide (poison
contained within marijuana and
tobacco smoke) inhibits cytochrome
oxidase – an important enzyme for
oxygen use by cells – lethal affect in
potent doses
b) Non-Competitive
Inhibitors bind to
enzyme (not at active
site) and this denatures
the enzyme
An example is heavy
metals, such as lead, &
DDT in the nervous
system.
[substrate]
Rate of Reaction
Another example of non-competitive inhibition is when a
metabolic product can feedback on a metabolic pathway to
control how much product is made.
The final product can temporarily attaches to the first
enzyme (not in the active site)
The enzyme will be denatured and the reaction will stop.
• Product B is substrate for 2nd reaction whose
product is substrate for 3rd reaction……. Until final
product is reached (G)
•B to F are known as intermediate product
Metabolic Pathway animation
This is an example of NEGATIVE FEEDBACK or FEEDBACK
INHIBITION.
When the concentration of the final product gets low again, there
will be less inhibition on the enzymes and the metabolic pathway
is reactivated.
ex – aa isoleucine is made from aa
threonine in a 5 step pathway:
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feedback inhibition
prevents cell from
wasting chemical
resources to
synthesize more than
is necessary
Thyroxin, the hormone that controls
the metabolic rate of all cells in your
body, is produced by the thyroid
gland in the neck.
If the [thyroxin] in your body is high,
your metabolic rate will be raised, and
if thyroxin levels are low, your
metabolic rate will be low.
http://ca.youtube.com/watch?v=VnneZReAT
W0
•Palpitations
•Heat intolerance
•Nervousness
•Insomnia
•Breathlessness
•Increased bowel movements
•Light or absent menstrual periods
•Fatigue
•Fast heart rate and trembling
hands
•Weight loss
•Muscle weakness
•Warm moist skin
•Hair loss
•Staring gaze