1 enzymes enzyme and digestion film clip enzyme and digestion film clip
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What Are Enzymes?
• Most enzymes are Proteins
• Act as Catalyst to accelerates 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
- Lipase - Protease
Enzymes Lower a Reaction’s Activation Energy
Activation Energy = energy needed to start a chemical reaction
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Enzymes
FreeEnergy
Progress of the reaction
Reactants
Products
Free energy of activationFree energy of activation
Without Enzyme
With Enzyme
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Enzyme-Substrate Complex
The substance (reactant) an enzyme acts on is the substrate
EnzymeSubstrate Joins
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Active Site
• An Active site of an enzyme molecule is where the substrate binds.
EnzymeSubstrate
Active Site
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Lock and Key Model
+ +
E + S ES complex E+ P
S
P
P
S
E = Enzyme S = Substrate P= product
Active site
The enzyme fits over the substrate perfectly – like a key fits a lock.
It holds the starch molecule in place as a water molecule breaks the bond between two glucose particles
Starch molecule
Amylase enzyme
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Induced Fit• A change in
the shape of an enzyme’s active site
• Induced or altered by the substrate
The active site of an enzyme is where substrate is bound.
Many Enzymes Work by Altering the Shape of Their Substrates
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Enzyme Action: Induced Fit Model
• Enzyme structure flexible, not rigid
• Enzyme and active site adjust shape to bind substrate
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Temperature & pH•High temperatures are the
most dangerous reactions & denature enzymes (Most like normal Body temperatures)
•Most enzymes like near neutral pH (6 to 8)
•Denatured (unfolded) by ionic salts and metal ions
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Cofactors and Coenzymes
• Inorganic substances (zinc, iron) and vitamins (respectively) are sometimes need for proper enzymatic activity.
Example: Iron must be present in the
protein structure of hemoglobin in order for it to pick up oxygen.
Digestive Enzymes
• There are 3 main types of digestive enzymes:– Amylase breaks starch down into
glucose.– Protease breaks protein down into
amino acids.– Lipase breaks fats down into fatty
acids and glycerol
Digestive Enzymes
Glycero
l
Fatty Acid
Fatty Acid
Fatty Acid
Glycerol
Fatty Acid
Fatty Acid
Fatty Acid
Lipase
Fat Fatty Acids and Glycerol
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Enzyme Inhibition
Inhibitors • Cause a loss of catalytic activity• Change the protein structure of
an enzyme• May be competitive or
noncompetitive• Some effects are irreversible• Poisons and drugs are
examples of enzyme inhibitors.
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Competitive Inhibition
A competitive inhibitor• Has a structure similar to
substrate• Occupies active site• Competes with substrate
for active site• Has effect reversed by
increasing substrate concentration
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