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Enzymes
Enzymes are biological catalysts
Proteins
Catalyst Lower activation energy Increases the rate of the reaction Affects nothing other than the reaction rate Does NOT affect the free energy of the reaction
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Bonds break, new bonds are formed releasing energyEnergy that is
absorbed in order to reach transition state
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Enzyme Activity is affected by…
Concentration of substrate
Concentration of enzyme
If enzyme is saturated, then rate is determined by enzyme’s rate for converting substrate to product
Cofactors / Coenzymes presence
Presence of Inhibitors
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Enzymatic Regulation
Enzymes = proteins Proteins have 3D
structure Affected by pH and
Temperature Structure & function
relationship
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Enzyme Assistants
Cofactors Nonprotein molecules that enzymes require
for catalytic activity Typically, inorganic
Such as zinc, iron, and copper
Coenzymes Organic cofactor (what does organic mean?) Vitamins
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Competitive Inhibition
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Questions
1. How does competitive inhibition differ from noncompetitive inhibition?
2. How does a cofactor differ from a coenzyme?
3. Name 3 things that affect enzyme activity?
4. What does an enzyme do?
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Pathway Regulation
2 main ways to regulate metabolic pathways: 1. Switching on/off genes 2. Regulating enzyme activity
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Allosteric Regulation
Allosteric – specific binding site NOT the active site!! Can be inhibition or activation
Allosteric molecule binds to a site other than the active site
Allosteric molecule binding enzyme shape change Change in enzyme shape active site shape change Structural change = Functional change
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Allosteric Regulation
Enzyme units oscillate between two conformational sites One is catalytically active, the other is
inactive
Regulatory site Called allosteric site Activator or inhibitor binds and stabilizes the
conformational form Usually an activator or inhibitor affects all
active sites
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Cooperativity
When a substrate molecule causes an induced fit in one active site triggers the same change in all subunits of the enzyme
Amplifies the response of enzymes to substrates Primes the enzyme to accept more substrate
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Feedback Inhibition
A metabolic pathway is switched off by the inhibitory binding of its end product to an enzyme that acts early in the pathway
An example of allosteric inhibition
Increases efficiency of a pathway Pathway is turned off when product
accumulates
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Final Questions
1. What happens to an enzyme in a chm rxn?
2. How does allosteric inhibition differ from noncompetitive inhibition?
3. What is the allosteric site?
4. How does cooperativity differ from allosteric activation?
5. What is the most effective method of pathway regulation?
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