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What Are Enzymes? proteinsMost enzymes are proteins catalystAct as a catalyst to accelerate a reaction Not permanentlyNot permanently changed in the process 2

3Enzymes catalyzeAre specific for what they will catalyze reusableAre reusable aseEnd in –aseExamples:-Sucrase-Lactase-Maltase

4 How do enzymes Work? weakening bonds, which lowers the activation energy Enzymes work by weakening bonds, which lowers the activation energy

Energy Used Without VS with enzyme: mations/Enzyme-Substrate/micro_enzyme- substrate.swf 5

6 Activation Energy Free Energy Progress of the reaction Reactants Products Free energy of activation Without Enzyme With Enzyme With an enzyme, the activation energy required to start the reaction is reduced

7 Enzyme-Substrate Complex Substratesubstance enzyme Substrate: the substance ( aka reactant) – an enzyme acts on Reactant: Reactant: element/compound enters the chemical reaction Enzyme Substrate Joins

8 Active Site Active siteregion enzyme bindsActive site: the region of an enzyme where the substrate binds. Enzyme Substrate Active Site

Lock and Key Theory Lock = enzyme Key = substrate Only correct key fits into the lock and will “react” 9

How enzymes work Identify: –Product –Substrate –Enzyme –Enzyme-substrate complex –Active site hill.com/sites/ /student_view0/ chapter2/animation__how_enzymes_work. html 10

What Affects Enzyme Activity? 1.Extreme Temperatures 1.Extreme Temperatures are the most dangerous.High temps may denature (unfold) the enzyme. 2.pH 2.pH (most like pH, near neutral) 3. Ionic concentration 3. Ionic concentration (salt ions) 4. Inorganic substances 4. Inorganic substances (zinc, iron) and vitamins Check this animation: m_2.htm m_2.htm 11

What is the optimum temperature for humans? 12

Practice Time! Stop here 13

14 Induced Fit shapeA change in the shape of an enzyme’s active site InducedInduced by the substrate

15 Induced Fit changeconfiguration enzyme’s active siteA change in the configuration of an enzyme’s active site (H+ and ionic bonds are involved). Inducedsubstrate.Induced by the substrate. Enzyme Active Site substrate induced fit

16 What Affects Enzyme Activity? Three factors:Three factors: 1.Environmental Conditions 2.Cofactors and Coenzymes 3.Enzyme Inhibitors

17 1. Environmental Conditions 1. Extreme Temperature are the most dangerous 1. Extreme Temperature are the most dangerous - high temps denature (unfold) enzyme. - high temps may denature (unfold) the enzyme. 2.pH (most like pH near neutral) 3.Ionic concentration (salt ions)

18 2. Cofactors and Coenzymes Inorganic substances (zinc, iron) vitamins enzymatic activityInorganic substances (zinc, iron) and vitamins (respectively) are sometimes need for proper enzymatic activity. Example:Example: Ironquaternary structure-hemoglobin pick up oxygen. Iron must be present in the quaternary structure - hemoglobin in order for it to pick up oxygen.

19 Two examples of Enzyme Inhibitors a. Competitive inhibitors: resemble enzyme’s normal substrate competeactive site a. Competitive inhibitors: are chemicals that resemble an enzyme’s normal substrate and compete with it for the active site. Enzyme Competitive inhibitor Substrate

20Inhibitors b.Noncompetitive inhibitors: do not enter the active sitebind to another part enzymeenzyme change its shape alters the active site 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. Enzyme active site altered Noncompetitive Inhibitor Substrate

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