Download Enzymes

Enzymes
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What are enzymes?
Enzymes are proteins (tertiary and quaternary
structures) that catalyze (act as catalysts) the rate
of a chemical reaction (increase).
They do this by decreasing the amount of activation
energy required for a reaction.
Not permanently changed
in the process
Enzymes
• Are specific for
what they will
catalyze
• Are Reusable
• End in –ase
-Sucrase
-Lactase
-Maltase
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Enzymes are very specific...
For example, the lipase substrate
(lipids) would not attach to amylase.
How do they work?
Activation energy is energy that chemicals need in order to
begin a reaction
Example: Frogs leaping
over a pile of rocks.
The higher the barrier
(activation energy) the
less frogs can get over
(or less product is
created).
How do enzymes Work?
Enzymes work by
weakening
bonds which
lowers
activation
energy
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Enzymes
Without Enzyme
With Enzyme
Free
Energy
Free energy of activation
Reactants
Products
Progress of the reaction
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H2O2 is a breakdown product of aerobic respiration. Catalase breaks down H2O2.
Catalase is in peroxisomes (in cells) and rid the body of toxins.
Peroxisomes are concentrated in the liver and the kidneys.
https://www.youtube.com/watch?v=ok9esggzN18
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Enzyme-Substrate Complex
An enzyme acts
on the
substrate
(chemical
substance)
Substrate
Joins
Enzyme
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Active Site
• A region of an enzyme molecule
which binds to the substrate.
Active
Site
Substrate
Enzyme
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Enzyme-Substrate Complex:
Lock and Key Theory
-The substrate attaches to the enzyme’s active site.
-Enzymes and substrates fit like a lock and key.
Without enzymes, every day reactions would be far
too slow for us to survive.
- Unable to break down toxic wastes in a timely manner.
- Unable to metabolize our food fast enough.
Life cannot
exist without
enzymes!
Induced Fit Theory
the enzyme changes its shape slightly to create a more
secure bond with substrate, and then the chemical
reaction follows.
Induced Fit
• A change in the
shape of an
enzyme’s active
site
• Induced by the
substrate
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After the chemical reaction, the product is released
from the enzyme.
The enzyme is free to carry on the same chemical
reaction again and again (enzymes can be reused).
What Affects Enzyme Activity?
• Four factors:
1. Environmental Conditions
2. Cofactors
3. Coenzymes
4. Enzyme Inhibitors
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1. Environmental Conditions
A. Extreme Temperatures are the
most dangerous
- high temps may denature (unfold)
the enzyme.
B. pH (most like 6 - 8 pH near
neutral)
C. Ionic concentration (salt ions)
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Factors that Affect Enzymes
-Two factors that affect enzyme productivity are pH and
temperature.
-Enzymes thrive best within certain temperature and
pH ranges, and cease functioning in others.
Example: people die of fevers
not because of the high
temperatures, but because
the enzymes in their body do
not function properly once the
temperature gets too high.
Examples of Enzymes
Enzyme
Substrate
(the Reactant)
Location in Body
Amylase
Carbohydrates / sugar
Mouth
Lipase
Fats
Various locations
Pepsin
Proteins
Stomach
Trypsin
Proteins
Small intestine
Lactase
Dairy
Small intestine
2. Cofactors and 3.Coenzymes
• Inorganic substances (zinc,magnesium,copper,iron) and organic
vitamins (respectively) are sometimes need for proper enzymatic
activity.
• Example 1:
Iron must be present in the quaternary structure hemoglobin in order for it to pick up oxygen.
zinc must be present to break down alcohol (alcohol
dehydrogenase)
Example 2:
The coenzymes make up a part of the active site, since without the
coenzyme, the enzyme will not function.
• vitamin B-12 - vitamin
• coenzyme B-12 - coenzyme
• Methyl group transfer - function
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Two examples of Enzyme Inhibitors
Many drugs are enzyme inhibitors as well as
chemicals such as herbicides and pesticides and
neurotoxins.
a. Competitive inhibitors: are chemicals that
resemble an enzyme’s normal substrate and
compete with it for the active site.
Substrate
Competitive inhibitor
Enzyme
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Inhibitors
b. Noncompetitive inhibitors:
Inhibitors that do not enter the active site,
but bind to another part of the enzyme
causing the enzyme to change its shape, which
in turn alters the active site.
The most common uses for enzyme inhibitors are as
drugs to treat disease, an example is drugs used in
chemotherapy, viagra, and anti-epilepsy medication.
Substrate
active site
altered
Enzyme
Noncompetitive
Inhibitor
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Enzymes play a critical role in everyday life.
Many heritable genetic disorders
(diabetes, Tay-Sachs disease) occur because
there is a deficiency or total absence of one or
more enzymes.
Other disease conditions (cancer) result
because there is an excessive activity of one or
more enzymes. Routine medical
tests monitor the activity of enzymes in the
blood, and many of the prescription
drugs (penicillin) exert their effects
through interactions with enzymes.
https://www.youtube.com/watch?v=XUn64HY5bug
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