1 Enzymes

2 What Are Enzymes? ProteinsMost enzymes are Proteins CatalystsAct as Catalysts to accelerates a reaction Not permanentlyNot permanently changed in the process ReusableReusable

3Enzymes Specific catalyzeAre Specific for what they will catalyze ReusableAre Reusable aseEnd in –ase-Sucrase-Lactase-Maltase

Enzymes and Substrates Enzymes are named for their substrates: “the substance that an enzyme acts on.” Substrate Enzyme Maltose   Maltase Lipid   Lipase Sucrose   Sucrase Proteins  ----  Protease/Pepsin Starch   Salivary Amylase ATP   ATPase 4

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

6Enzymes Free Energy Progress of the reaction Reactants Products Free energy of activation Without Enzyme With Enzyme

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

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

9 What Kind of Reaction Is This?

10 Lock and Key Model same shapeThe Active Site of an enzyme is the same shape as the substrate

Lock and Key Model cont. Right Shape” Only enzyme with the “Right Shape” will work with a specific substrate 11

AB C+ H 2 O A + B -- enzyme  C + H 2 O products substrate products substrate Enzymatic Dehydration Synthesis

Enzymatic Hydrolysis C+ H 2 OAB C + H 2 O -- enzyme  A + B substrate products substrate products Also See:

14 Factors Affecting Enzyme Activity Temperature pH Cofactors & Coenzymes Inhibitors Enzyme Concentration Substrate Concentration

15 Temperature & pH High temperatures denature (Most like normal Body temperaturesHigh temperatures are the most dangerous reactions & denature enzymes (Most like normal Body temperatures) Most enzymes like near neutral pH (6 to 8) ionic saltsDenatured (unfolded) by ionic salts

Enzymes and Temperature Enzymes and Temperature. Low temperatures - enzymes are inactive. As temperature h enzymes activity h (reactions speed up). Each enzyme has an optimum temperature. When temperature gets too high, enzymes are destroyed, or denatured. ( see animations next two pages ). Substrate concentration constant

Enzyme Denatured Heat

Active site is deformed and no longer functions

Enzymes and pH Each enzymes work best at optimum pH. If the pH is very high or very low, enzymes can be denatured. Substrate concentration constant

Rate of an enzymatic reaction as a function of temperature and pH

21 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 : Iron hemoglobin oxygen Iron must be present in the structure of hemoglobin in order for it to pick up oxygen.

Coenzymes Some enzymes need Coenzymes to function properly. Vitamins often function as Co-enzymes ex. niacin Coenzyme

23 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

24Inhibitors 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

Rate of enzyme activity as a function of Substrate Concentration

Rate of enzyme activity as a function of Enzyme Concentration *Substrate concentration held constant Enzyme Concentration

Enzyme Review See Mr. Wanamaker’s site port.com/ /lib/ /Animations/Enzyme_activity.htmlwww.lew- port.com/ /lib/ /Animations/Enzyme_activity.html

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