2 Catalysts and Enzymes Why are enzymes important? hundreds of chemical reactions are in progress in a typical living cell at a given momentThese reactions provide energy and substances needed for growth and repairChemical reactions would not be possible without ENZYMES
3 Watch a catalyst in action! CatalystsCatalyst = a chemical that speeds up the rate of a chemical reactionIs not used up in the reactionWatch a catalyst in action!
4 Enzymes are everywhere! Enzyme = an organic catalystMade up of proteinsAllow chemical reactions to happen at room temperatureSpeed up reactions without increasing temperature!Enzymes are everywhere!In saliva…… stomach… even mitochondria!
5 Draw the picture below to show how an enzyme works: SubstrateProductsActive SitesEnzyme-Substrate ComplexEnzymeWhat type of reaction is this?Hydrolysis or catabolic reaction.
6 Why are enzymes necessary? Chemical reactions normally occur very SLOWLY!Increasing temperature increases the rate of reactionBut increasing temperature too much will denature proteins and damage our cells!Enzymes speed up the rate of a reaction without increasing the temperature
7 Activation EnergyChemical reactions require an initial energy input to startEx: Rock must be rolled up the hill before it is able to roll down the other side of the hill by itselfActivation Energy = energy required to initiate (start) a chemical reaction
8 Enzymes do not change the amount of energy available! Activation EnergyNo enzyme = higher activation energyWith enzyme =lower activation energyEnzymes do not change the amount of energy available!
9 3-2 Enzymes are Substrate Specific Substrate: a molecule which attaches to the active site of an enzymeActive site: Area of an enzyme that combines with a substrate moleculeEach enzyme is specific for a particular substrate- Like lock and key
11 Naming of enzymesEnzymes are given unique names based on the specific substratesEnzyme name = name of the substrate + ASESucraseSucrose + H2OFructose + Glucose
12 Naming Enzymes: Fill in the following table!! SubstrateEnzymeMaltoseLactoseProteinStarchLipidsPolypeptides“ase”!MaltaseLactaseProteaseNot all enzymes endwith “ase”!! Pepsinand Trypsin areprotein enzymesthat do not endin “ase”AmylaseLipasePeptidase
13 Not all enzymes end with “ase” Not all enzymes end with “ase”!! Pepsin and Trypsin are protein enzymes that do not end in “ase.”stomachpancreas
14 3-3 Basic Mechanism of Enzyme Action Chemical reactions occur when molecules collide or bonds are brokenEnzymes increase the probability of reactions occurring inside cells by bringing substrate molecules CLOSER togetherEnzymes can form bonds between molecules or break bonds
15 Lock and Key Hypothesis The active site of the enzymes fits the substrate moleculesThis forms an enzyme substrate complexProduct
16 Enzyme – Lock and Key Hypothesis BBDFA: substratesB: enzymeC: active siteD: enzyme-substrate complexE: productsF: enzyme to be used again
17 3-4 Coenzymes and Cofactors Recall:Cofactors are inorganic moleculesExamples: iron, zinc, calcium, magnesium and potassiumCoenzymes are organic molecules such as vitamins
18 Enzymes may not act alone... Sometimes additional chemicals are necessary ingredients to permit enzyme activityEnzyme co-factors and co-enzymes are often linked with enzyme activityCoenzymes and cofactors change the shape of the active site on the enzyme!Where a co-enzyme is lacking, enzyme activity may be reduced
20 Coenzymes and Cofactors What happens when someone has a poor diet???The chemical reactions requiring coenzymes (vitamins) and cofactors (minerals) cannot work when someone has a poor diet!!
21 Other factors affecting Enzyme Activity a) Temperature Enzymes have an optimum temperature where the greatest number of molecular collisions occursAn increase in temperature causes an increase in reaction rateMore molecules = more collisionsOptimum temperature range of most human enzymes is 35-40oCExamples of optimum temperatures:Hot springs bacteria = 85oCAntarctic ice fish = 2oC
22 highest rate of chemical reactions Temperature cont…High temperatures cause enzymes to denature (change shape)Why do you think high fevers for long periods of time are dangerous?Optimal temperature =highest rate of chemical reactionsReactionrateEnzyme denatures37oCTemperature
23 Effects of pHOptimal pH for most enzymes is pH 6-8 but some operate at more extremesThe enzyme pepsin has a optimal pH of 2A pH above or below the optimal pH may cause denaturationEnzyme activity will lower because the shape of the enzyme has changed…
25 Substrate Concentration As substrate concentration increases, enzyme activity increasesAs enzyme active sites become full, if the number of substrate molecules exceed the number of enzymes molecules, then the reaction levels off.No more enzymes available =reaction rate leveling offReactionrateMore substrate for the enzymeto use = increasing reaction rateSubstrate concentration
26 Competitive Inhibitors Inhibitors have shapes very similar to the substrate and also bind to the active site of the enzymeWhen an inhibitor combines with the enzyme it prevents it from functioning properlyInhibitor must be removed for normal functioning to occurdecreases enzyme activity by filling the active site so substrates cannot join!
27 Examples of competitive inhibitors include carbon monoxide, cyanide and penicillin
28 Carbon Monoxide (CO)Many poisons and drugs act as competitive inhibitors…CO for example competes with oxygen for the active site on the hemoglobin molecule.In fact, it binds to hemoglobin 200X faster than oxygen! Once CO fits itself in, it rarely is dislodged
29 CyanideCyanide attaches to enzyme in mitochondria, preventing the breakdown of sugars for energy. Cell dies!!Without the energy needed for active transport, protein synthesis, transport of nutrients, and elimination of wastes, a cell dies almost instantly!
30 Penicillin Penicillin kills invading bacteria Blocks an enzyme necessary for the synthesis of protective walls in bacteriaNo effect on human enzymes
31 Topic 3-6: Control of Enzyme Activity Many substances in the cell are produced by a metabolic pathway (a series of many chemical reactions involving enzymes)Feedback inhibition = High levels of a substance will result in a decrease in its production