2 What are enzymes?enzymes are proteins that function as biological catalystsa catalysts is a substance that usually speeds up the rate of a chemical reaction and is not changed by the reactionthus enzymes speed up the rate of metabolic reactions in the cells
3 Enzymes workenzymes lower the minimum amount of energy required for chemical reaction to occur (activation energy)this allows biochemical reactions to take place at a faster rate in the cells of living organisms at body temperature which is usually lowenzymes catalyse metabolic reactions (i.e. chemical reactions that sustain life) in a cellsmetabolic reactions are either breakdown reactions - catabolism or build up reactions - anabolism
4 Naming of EnzymesEnzyme are named according to the reaction they catalyseA suffix – ase is usually added to the name of the substrate of the reaction catalysed by the enzymeSometimes they are given special names such as catalase & amylaseCatalase is the fastest acting enzyme
6 “Lock and Key” ModelEach enzyme has a shape that allows it to catalyse one reactionReactant(s) in an enzyme – catalysed reaction is/are called substrate(s)Enzyme’s molecule has a specific shape which is complementary to that of a substrate –this is called active siteThe substrate fits into the active site of the enzyme the same way a ‘key fits into a lock’ - this is called “ lock and key” modelThe substrate (the ‘key’) fits exactly into the active site (the ‘key hole’) of the enzyme (the ‘lock’)An enzyme-substrate complex is formed.The substrate undergoes a chemical change – a new substance, the product, is formedThe product is released from the active site.The free unaltered active site is ready to receive fresh substrate.
8 General Properties of Enzymes enzymes are all Proteinsenzymes are Specific in reaction they catalyseenzymes are not changed by the reaction they catalyse i.e. they can be used again and againenzymes are influenced by change in temperatureenzymes are influenced by change in pHenzymes work best at particular temperature (37 oC in humans)and pH (pH 2 for pepsin & pH 7 for most enzymes)
9 Factors Affecting Enzyme Activity Enzyme activity is determined by measuring the rate of reaction that the enzyme catalysesThis is usually measured by measuring the products formed per unit timeEnzyme activity is affected by;temperature,pH &substrate concentration
10 Effect of Temperature on Enzymes at low temperature (e.g. 0°C) enzyme activity is low because the movement of molecules is slow due to low kinetic energythe collision frequency between enzyme and substrate is therefore lowincreasing the temperature, increases kinetic energy of molecules thus speeding up their movement, collision frequency between the substrates and the enzymes increases therefore enzyme activity increasesmaximum enzyme activity is at 40°C – due to maximum collision frequency between enzymes and substrates molecules – this is called optimum temperature (i.e. the temperature at which the enzyme works fastest)enzyme action decreases above 40°C because the enzymes are denatured by excess temperature (i.e. the shape of active site is altered & substrates molecules can no longer fit into it)when all the enzymes are denatured, at 60°C, enzyme activity stops
11 Effect of pH on Enzymesenzyme activity is greatest within a narrow range of pH, since all the enzymes are functioning normally because their active sites have the correct shapethis is called the optimum pHchange in pH from the optimum, alters the shape of active site thus affecting the ability of the substrates to bind to the active site & so enzyme activity decreasesa major change in pH from the optimum denatures the enzymes so enzyme action stopsWhat is the optimum pH for;enzyme X?enzyme Y?
12 Use of enzymes in: germination of seeds, biological washing products & food industry Enzymes are widely used in industry because;they work at lower temperature than other catalysts thus reducing cost of fuelthey are not destroyed by the reaction the catalyse, thus they can be used over and over againApplications of enzymes in day – to – day life include;Hydrolysis of stored food during seed germinationsUse of enzymes in food industry such as juice extraction, brewing industry to make beerMaking of biological washing powdersProducing antibiotic penicillin
13 Use of enzymes in: germination of seeds enzymes in seeds breakdown stored food substance into soluble end products which can be translocated to growing regionsstarch is broken down to maltose by the enzyme amylasefats/oils are broken down by lipase to fatty acids and glycerolmaltose & fatty acids are respired to provide energy for germination
14 Production of apple juice enzyme pectinase is added to crushed apple fruit pulpthe enzyme breaks down pectin in plant cell walls releasing more juice from the crushed apples
15 Use of enzymes in biological washing powders presence of enzymes in biological washing powders increase the efficiency of the washing powder in removing stains from clothes because:stains may be protein or fat which are not removable with detergent onlypresence of lipase breaks down fat stain into fatty acids & glycerolpresence of protease breaks down protein stain into amino acidsfatty acids, glycerol & amino acids are soluble in water thus easily washed away
16 Controlling the temperature of the wash temperature of the wash needs to be carefully controlled because:high temperature denatures enzymes , so enzymes will not workat low temperature, enzymes are inactive thus they work slowlyconstant optimum temperature such as 37 oC maintains optimum conditions for enzyme activity
17 Use of microorganisms & industrial fermenters to manufacture the antibiotic industrial fermenters are large metal tanks that uses microorganisms to produce useful products such as antibiotics such as penicillinthe organism involved, fungus Penicillium is added to the tank together with nutrients such as sugar & ammonium salts (or amino acids)Penicillium produce enzymes which converts the substrate into penicillin, antibiotic used to cure bacterial infectionssugar provide energy for respiration while ammonium salt is used to produce proteins & nucleic acids
18 Maintaining suitable conditions in the industrial fermenters suitable conditions such as optimum pH, optimum temperature and supply of oxygen & nutrients are requiredair is bubbled through to provide oxygen for respirationstirring using paddles keeps microorganism suspended so they always have access to nutrients & O2 and rolls the fungus into little pellets making it easy to separate liquid from the culturewater -cooled jacket maintains a constant temperature of 24 oCprobes monitor the temperature & pH in the tank. pH is maintained at 6.5 by adding alkalis where necessaryafter 6 days, fermentation is complete & the mixture is drained & filteredpenicillin is then extracted
19 Role of the fungus Penicillium in the production of antibiotic penicillin fungus penicillium produces enzymes that converts the substrate into penicillin, antibiotic used to cure bacterial infections
20 Revision activityAfter reading pages of your biology textbook and your lesson notes, attempt Revision Questions on page 48.