1 Enzymes

2 What Are Enzymes? Proteins (Most enzymes are Proteins (tertiary and quaternary structures) CatalystAct as Catalyst to accelerates a reaction Not permanentlyNot permanently changed in the process

3Enzymes catalyzeAre VERY specific for what they will catalyze ReusableAre Reusable aseNames end in –ase-Sucrase-Lactase-Maltase

4 How do enzymes Work? weakening bonds which lowers activation energy Enzymes work by weakening bonds which lowers activation energy Activation energy is the amount of energy needed to start a reaction

5Enzymes Free Energy Progress of the reaction Reactants Products Free energy of activation Without Enzyme With Enzyme

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7 Enzyme-Substrate Complex substrate is the substance enzyme The substrate is the substance (reactant) an enzyme acts upon Enzyme Substrate Joins

8 Active Site active siterestricted region enzymebinds substrateThe active site is a restricted region of an enzyme molecule which binds to the substrate. Enzyme Substrate Active Site

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

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

11 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) – the active site has a slight charge to it

12 2. Cofactors and Coenzymes Inorganic substances (cofactors - zinc, iron) vitamins enzymatic activityInorganic substances (cofactors - zinc, iron) and vitamins (coenzymes) 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. Vitamins are precursors to coenzymes.

13 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

Examples of competitive inhibitors: –Caffeine in your brain – prevents the release of a chemical that slows down brain activity –Antivirals used to treat HIV – interfere with HIV’s ability to reproduce itself 14

15Inhibitors 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

Examples of noncompetitive inhibition –ATP turns off enzymes that produce ATP –Sulfa drugs that destroy microorganisms 16