Enzymes

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Enzymes

  1. 1. EnzymesT- 1-855-694-8886Email- info@iTutor.comBy iTutor.com
  2. 2. What is an enzyme? A biological catalyst that promotes and speeds upa chemical reaction without itself being altered inthe process. Lowers the activation energies of a substance© iTutor. 2000-2013. All Rights Reserved
  3. 3. Properties of enzymes1) Enzymes are proteins, thus activity easily affected bytemperature & pH.2) Enzymes increases the rate of reaction by lowering theactivation energy barrier, thus allowing reactions to proceedwithout an input of energy.3) Mechanism: forms enzyme-substrate complex to facilitate theirinteraction and reaction.© iTutor. 2000-2013. All Rights Reserved4) An enzyme only changes the rate at which equilibrium isreached; it does not affect the position of the equilibrium.5) A small quantity of the enzyme is needed for the reactionbecause they are unchanged at the end of the reaction.6) Enzymes catalyze reactions which are specify to themselves.
  4. 4. Structure of EnzymesEnzymes are Proteins that: Increase the rate of reaction by lowering the energy of activation. Catalyze nearly all the chemical reaction taking place in the cellsof the body. Have a unique three dimensional shapes that fit the shapes ofreactants.© iTutor. 2000-2013. All Rights Reserved Increasing the temperature make molecules move faster. Biological systems are very sensitive to temperature changes. Enzymes can increase the rate of reactions without increasingthe temperature. They do this by lowering the activation energy. They create a new reaction pathway “a short cut”
  5. 5. An enzyme controlledpathway Enzyme controlled reactions proceed 108 to 1011 times faster thancorresponding non- enzymic reactions.© iTutor. 2000-2013. All Rights Reserved
  6. 6. Specificity All enzymes operate only on specific substrate: some enzymes will act only on one particular substrate; others act on similar molecules; many will break a particular linkage, e.g. hydrogen bondsProperties of enzymes© iTutor. 2000-2013. All Rights ReservedReversibility Enzymes do not alter the equilibrium of a reaction but thespeed at which it is reached, e.g. carbonic anhydraseCO2 + H2O ———— H2CO3————carbonicanhydrase
  7. 7. Factors affecting Enzymes Substrate concentration pH Température Inhibitors© iTutor. 2000-2013. All Rights Reserved
  8. 8. Substrate concentration: Enzymicreactions Faster reaction but it reaches a saturation point when all the enzymemolecules are occupied. If you alter the concentration of the enzyme then Vmax will changetoo.ReactionvelocitySubstrate concentrationVmax© iTutor. 2000-2013. All Rights Reserved
  9. 9. The effect of pHOptimum pH valuesEnzymeactivity TrypsinPepsinpH1 3 5 7 9 11© iTutor. 2000-2013. All Rights Reserved
  10. 10. The effect of pH Extreme pH levels will produce denaturation. The structure of the enzyme is changed The active site is distorted and the substrate molecules will nolonger fit in it At pH values slightly different from the enzyme’s optimumvalue, small changes in the charges of the enzyme and it’ssubstrate molecules will occur This change in ionisation will affect the binding of thesubstrate with the active site.© iTutor. 2000-2013. All Rights Reserved
  11. 11. The effect of temperature For most enzymes theoptimum temperature is about30°C Many are a lot lower; coldwater fish will die at 30°Cbecause their enzymesdenature A few bacteria have enzymesthat can withstand very hightemperatures up to 100°C Most enzymes however arefully denatured at 70°C© iTutor. 2000-2013. All Rights ReservedTemperature / °CEnzymeactivity0 10 20 30 40 50TemperaturecoefficientDenaturation
  12. 12.  Irreversible inhibitors: Combine with the functional groups of theamino acids in the active site, irreversibly. Examples: nerve gases and pesticides, containing organphosphorus, combine with serine residues in the enzymeacetylcholine esterase.© iTutor. 2000-2013. All Rights ReservedThe effect of enzyme inhibition Reversible inhibitors: These can be washed out of thesolution of enzyme by dialysis.There are two categories.Competitive: These compete with the substrate molecules for the activesite. The inhibitor’s action is proportional to its concentration. Resembles the substrate’s structure closely.
  13. 13. Succinate Fumarate + 2H++ 2e-Succinate dehydrogenaseCH2COOHCH2COOH CHCOOHCHCOOHCOOHCOOHCH2Malonate© iTutor. 2000-2013. All Rights Reserved Non-competitive: These are not influenced by the concentration of thesubstrate. It inhibits by binding irreversibly to the enzyme but not at theactive site. Examples : Cyanide combines with the Iron in the enzymes cytochrome oxidase. Heavy metals, Ag or Hg, combine with –SH groups. These can be removed by using a chelating agent such as EDTA.
  14. 14. Enzymatic ReactionsEnzyme combines with a specific substrate to a form anenzyme-substrate complex in a lock and key conceptbefore forming new products.© iTutor. 2000-2013. All Rights Reservedenzymesubstrateproducts
  15. 15. Applications in food industry Carbohydrases: Production of corn syrups from starch (glucoamylase);conversion of cereal starches into fermentable sugars inmalting, brewing, distillery, baking industry (amylase). Proteases: Meat tenderizers (bromelin, papain, ficin) Lipases: Flavor production in chocolate and cheese Glucose Oxidase: Desugaring of eggs, flour and potatoes; preparation ofsalad dressings. Pectinases: Clarification of fruit juices; increase of yield of juice from grapesand other products; removal of excess pectin from juices beforeconcentration. Lipoxygenase: Bleaching of flours. Phosphatase: Quality testing of food products. Phenol oxidase: Imparts the characteristic. dark hue to tea, cocoa, coffeeand raisins. Renin (chymosin): Cheese production.© iTutor. 2000-2013. All Rights Reserved
  16. 16. ENDCall us for moreInformation:www.iTutor.com1-855-694-8886Visit

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