1 Enzymes

Chemical Reactions Reactions begin with reactants and result in products ReactantsProduct CO 2 + H 2 0H 2 CO 3

Chemical reactions always involve changes in the chemical bonds that join atoms in compounds.

Energy in Reactions Most chemical reactions require energy to get started. Chemists call the energy required to start a reaction “Activation Energy”

Catalysts and Enzymes A catalyst is a substance that speeds up chemical reactions. Lighter Fluid is a catalyst for a campfire. Enzymes are proteins that act as catalysts by speeding up chemical reactions that take place in cells.

Substrates Reactants that an enzyme works on are called substrates.

7 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

8Enzymes catalyzeAre specific for what they will catalyze ReusableAre Reusable aseEnd in –ase-Sucrase-Lactase-Maltase

9 How do enzymes Work? weakening bonds which lowers activation energy Enzymes work by weakening bonds which lowers activation energy

10Enzymes Free Energy Progress of the reaction Reactants Products Free energy of activation Without Enzyme With Enzyme

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

13 Active Site restricted region enzyme bindssubstrateA restricted region of an enzyme molecule which binds to the substrate. Enzyme Substrate Active Site

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.Chemicals that block the enzyme 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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