Slide 1 of 50 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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Slide 4 of 50 Bonds break, new bonds are formed releasing energy Energy that is absorbed in order to reach transition state

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Slide 7 of 50 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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Slide 9 of 50 Enzymatic Regulation  Enzymes = proteins  Proteins have 3D structure  Affected by pH and Temperature  Structure & function relationship

Slide 10 of 50 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

Slide 11 of 50 Competitive Inhibition

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Slide 14 of 50 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?

Slide 15 of 50 Pathway Regulation  2 main ways to regulate metabolic pathways:  1. Switching on/off genes  2. Regulating enzyme activity

Slide 16 of 50 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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Slide 18 of 50 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

Slide 19 of 50 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

Slide 20 of 50 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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Slide 22 of 50 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?