2 Enzymes are Biological Catalysts What are enzymes?Biological catalysts made up of protein which alter rate of chemical reaction without themselves beingchemically changed at the end of reactionsCatalysts : Substance that increase rate of reaction without being used up.
3 Enzymes are Biological Catalysts Enzymes are made up of proteinDenatures (enzyme loses it shape and function) if exposed to high temperature or extreme changes in pHSpeeds up reaction without the need to increase temperature.
4 Mode of actions of enzymes Breaking down of fatsHeat at high temperatureUsing enzymesBody cannot withstand high temperaturesEnergy is required to start breaking down fats – activation energyEnzymes lower activation energy > Required to start chemical reaction.
5 Enzymes-catalysed Reactions DigestionProcess whereby large insoluble food substances are broken down into small soluble moleculesCarbohydrates MonosaccharidesProtein Amino AcidsFats Fatty Acids + Glycerol
6 Enzymes-catalysed Reactions 2. Synthesis of complex substances from simpler ones.Synthesis of proteinsSynthesis of glycogen for storage in the bodySynthesis of fats
7 Enzymes-catalysed Reactions 3. Oxidation of GlucoseRelease of Energy to do workInvolves a series of enzyme catalysed reactions4. Breakdown of toxic materialsHydrogen peroxide to water and oxygen catalysed by catalase.Enzymes catalyse almost all reactions in body.There are many different types of enzymes and eachis specific and will be produced only when required.
8 Classifying Enzyme According to chemical reaction they catalyse Usually ends up with –aseExample:Breaking down of starch = amylaseBreaking down of Protein = ProteaseBreaking down of Lipids/Fats = LipaseEnzyme combine with molecules it acts upon (substrate) to form an enzyme-substrate complex.Enzyme controlled reaction can be eitherAnabolic : building up larger moleculesCatabolic: breaking down large molecules into smaller molecule
9 Characteristics of Enzymes Speeds up rate of chemical reactionsRequired in minute amount (small) – (itself not breakdown)Specific (Lock & Key hypothesis)
10 Lock & Key HypothesisSubstrate which the enzyme acts on is called substrateExample: Breaking down of starch, amylase is the enzyme and starch is substrate. End-product = MaltoseEnzyme molecules are usually larger than substrateSmall part of enzyme, called active site comes into contact with substrateEnzyme (lock) and substrate(key)Enzyme(lock)Substrate (Key)ProductAmylaseStarchMaltoseLipaseLipidFatty acids + glycerolProteaseProteinAmino acids
11 Active siteEnzyme substrate complexamylasestarch2 maltose unitsamylase
12 Enzyme are affected by temperature Enzyme and substrate in constant motionIncrease temperature results in increased kinetic energyMolecules move fasterRate of enzyme colliding with substrate is higherRate of enzyme-substrate complex formed higherOnly up to an optimum temperatureLow temperature = enzymes are inactive
13 Enzyme are affected by temperature Around 37 ℃ in mammalsToo high a temperature will result in protein being denaturedActive sites change shape and activity gradually declineDifferent enzymes can withstand different temperature rangeMost enzymes will be completely denatured above 60 ℃Molecules move slower and rate of collision lower
14 Q: How does temperature affect Enzyme activity What happens at low temperature?Enzyme are inactive at low temperatureWhat happens as temperature increase?As temperature increase, enzymes gain more kinetic energy causing them to move faster. When they move faster, chances of colliding into a substrate is higher. Hence, rate of forming enzyme-substrate complex is higher. Rate of reaction increasesWhat happens at optimum temperature?At optimum temperature, enzyme are most activeWhat happens above optimum temperature?Enzymes loses active sites, denatured.
15 Enzymes are affected by temperature: Activeness of enzymes0 ℃50 ℃100 ℃
16 Enzyme are affected by pH Enzyme usually work efficiently within a narrow pH range.Some enzymes works best in slightly acidic conditions (pepsin and rennin) while others in slightly alkaline conditions.Extreme pH will result in denaturation of enzymesLowHighTemperatureInactiveDenaturedpH valuedenatured
17 Enzymes are affected by pH: Activeness of enzymespH 1pH 7pH 14
18 Enzyme are affected by Enzyme concentration Increase enzyme concentration, increased rate of reactionTemperature and pH are at optimum valuesSubstrate level must be high.
19 Enzyme are affected by substrate concentration Concentration of enzyme remains the sameIncreased substrate concentration doesn’t necessarily increase rate of reactionActive sites become saturated, therefore could not work any faster
20 For example, you are making burgers with buns and the number of patties you have is limited.Buns = Substrate, Patties = Rate of reaction5No. of patties(Rate ofReaction)4321Number of buns(substrate)246810
21 Enzyme are affected by substrate concentration How do you know that substance is not enough?When I increase number of substance, I can produce more burgers (Also: When I increase number of that substance, there is an increase of rate of reaction)
22 Limiting FactorsAny factor that directly affects the rate of reaction if its quantity is changedValue of this factor has to be increased in order to increase rate of reaction
23 D C A B Reversible Reactions Most reactions in living cells are reversible.Enzyme can catalyse reversible reactionsUsually not allowed as products formed are used up or transported away.REACTANTS PRODUCTSDCBAPRODUCTS REACTANTS