Enzymes
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• Brief introductory enzyme video:
• https://www.youtube.com/watch?v=vTQybDgweiE
• Goofy video on how enzymes work:
• https://www.youtube.com/watch?v=XTUm-75-PL4
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What Are Enzymes?
• Most enzymes are
Proteins (tertiary
and quaternary
structures)
• Act as Catalyst to
accelerate a
reaction
• Not permanently
changed in the
process
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Enzymes
• Are specific for
what they will
catalyze
• Are Reusable
• End in –ase
-Sucrase
-Lactase
-Maltase
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How do enzymes Work?
Enzymes work by
lowering
activation
energy which
speeds up a
reaction
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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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Enzyme-Substrate Complex
The substance
(reactant) an
enzyme acts on
is the substrate
Substrate
Joins
Enzyme
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Active Site
• A restricted region of an enzyme
molecule which binds to the substrate.
Active
Site
Substrate
Enzyme
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Induced Fit
• A change in the
shape of an
enzyme’s active
site
• Induced by the
substrate
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Induced Fit
• A change in the configuration of an
enzyme’s active site (H+ and ionic
bonds are involved).
• Induced by the substrate.
Active Site
substrate
Enzyme
induced fit
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What Affects Enzyme Activity?
• Three factors:
1. Environmental Conditions
2. Cofactors and Coenzymes
3. Enzyme Inhibitors
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1. Environmental Conditions
1. Extreme Temperature are the most
dangerous
- high temps may denature (unfold)
the enzyme.
2. pH (most like 6 - 8 pH near
neutral)
3. Ionic concentration (salt ions)
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2. Cofactors and Coenzymes
Inorganic substances (zinc, iron) and
vitamins (respectively) are sometimes needed
for proper enzymatic activity.
• Example:
Iron must be present in the quaternary
structure - hemoglobin in order for it to
pick up oxygen.
Other enzymes are sometimes needed to
activate another enzyme.
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Our food is made up of:
• Carbohydrates: Bread, Pasta, Potato
• Protein: Meat, Nuts, Lentils
• Fats: Butter, Milk
Our body needs to digest them – turn
them into a form that can be absorbed
into the blood and used by cells.
Enzymes make this possible.
Enzyme video/animation: https://www.youtube.com/watch?v=r1ryDVgx0zw
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Enzymes that work on carbohydrates:
Salivary Amylase + Starch 
Maltose
(in saliva)
(in pasta, bread
(a form of sugar that
carbohydrate)
can be absorbed
by the body )
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Enzymes that work on Proteins:
Protease
(in stomach)
+ Proteins 
(eg. In meat, nuts)
Amino Acids
(the body can absorb
them and use them)
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Enzymes that work on Fats:
Lipase + Fats
 Fatty Acids + Glycerol
(secreted by pancreas)
(Butter, Milk)
(can be
absorbed into body)
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