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Enzymes
- 1. Enzymes
- 2. Learning Objectives At the end of the lessons, students should be able to: • Define what is an enzyme • Explain enzyme action in terms of the ‘lock and key’ hypothesis. • Explain the mode of action of enzymes in terms of an active site, enzyme-substrate complex, lowering of activation energy and enzyme specificity. (PURE) • Investigate and explain the effects of temperature, pH on the rate of enzyme catalysed reactions.
- 3. What are Enzymes?? *Take note of what are enzymes and their functions
- 4. What are Enzymes? •Biological catalyst made of protein •Speed up chemical reactions in living organisms without themselves being chemically changed at the end of the reactions
- 5. Some important Terminologies Substrates (Reactants) • Substances on which enzymes act on • Eg: Starch (substrate) which salivary amylase acts on Active Site • Depressions on the surface of an enzyme molecule where the substrate can fit
- 6. Some important Terminologies Products • Substance obtained after an enzymatic reaction
- 7. How does Enzymes work? Picture this… Enzymes Complex molecules Simpler molecules
- 8. How does Enzymes work? Picture this… Enzymes Simple molecules Complex molecules What is needed for the a chemical reaction to take place?
- 9. •To start a chemical reaction, a certain amount of energy is needed. •This amount of energy is called activation energy How does Enzymes work? Pg 7
- 10. •Enzymes work by lowering the activation energy required to start the reaction. • In this way, the reaction is sped up How does Enzymes work? Pg 7
- 11. Enzymes lowers the activation energy of chemical reactions
- 12. What are the types of Enzyme Reactions? Break down complex substances Build up complex substances
- 13. Types of Enzyme Reactions Break down complex molecules into simpler molecules • E.g. digestion of maltose to glucose maltase
- 14. Types of Enzyme Reactions Build up complex molecules from simpler molecules • E.g. Glucose Glycogen Glycogen synthase GlycogenGlucose molecules
- 15. Classification of Enzymes Type of Enzyme Carbohydrase Protease Lipase Type of Substrate Fats/ Lipids Protein Carbohydrates Example of Enzyme Maltase Pepsin Intestinal Lipase
- 16. Properties of Enzymes 1. Speeds up chemical reaction 2. Required in small amounts 3. Specific in action 4. Affected by temperature 5. Affected by pH 6. Catalyse reversible reactions
- 17. 1. Enzymes speed up chemical reaction Properties of Enzymes • By lowering the activation energy needed to start the reaction
- 18. 2. Enzymes are required in minute amounts Properties of Enzymes • Enzymes remain chemically unchanged after a chemical reaction • Can be reused again & again
- 19. 3. Enzymes are specific in action Properties of Enzymes • One kind of enzyme will catalyse only one kind of chemical reaction • Substrate specific (Lock & Key hypothesis)
- 20. 4. Enzymes are affected by temperature Properties of Enzymes • Enzymes are made up of proteins • Enzymes denatures at high temperatures • Enzymes are inactive at low temperatures
- 21. Effect of Temperature on Enzyme Reaction
- 22. Effect of Temperature on Enzyme Reaction A • Enzymes are inactive at very low temperatures • Low rate of reaction Enzymes are not destroyed at very low temperatures
- 23. Effect of Temperature on Enzyme Reaction B • Enzyme activity increases as temperature rises • Rate of reaction increases Molecules moves faster in higher temperatures, substrate & enzyme will collide more often
- 24. Effect of Temperature on Enzyme Reaction C • Enzyme activity reaches its maximum rate • At the optimum temperature Most enzymes have an optimum temp of 40 oC
- 25. Effect of Temperature on Enzyme Reaction D • Enzyme rate of reaction decreases ZERO • The enzymes denatures The structure of the active site changes substrate cannot bind rxn decreases
- 27. Virtual Lab Experiment • http://www.mhhe.com/biosci/genbio/virtual_labs/BL_11/BL_11.html
- 28. 5. Enzymes are affected by pH Properties of Enzymes • Enzymes are made up of proteins • Enzymes denatures at extreme pH • Acidic / Alkaline
- 29. Effect of pH on Enzyme Reaction • Optimum pH: • The pH value at which the rate of enzyme reaction is the highest • Extreme pH: • Denatures enzymes • Changes the structure of the active site
- 30. Effect of pH on Enzyme Reaction Rateofreaction
- 31. 6. Enzymes catalyse reversible reactions Properties of Enzymes • Reactions can proceed in forward and backward direction • Eg: CO2 H2CO3H2O+ carbonic anhydrase WaterCarbon dioxide Carbonic acid
- 32. The enzyme & substrate molecules will combine to form a temporary structure called enzyme-substrate complex Some important Terminologies
- 33. Action of Enzyme (Build Up Reaction) enzyme substrate enzyme product enzyme- substrate complex Pure
- 34. Action of Enzyme (Break Down Reaction) enzyme product enzyme substrate enzyme- substrate complex Pure
- 35. Which statement is true of all enzymes? Micro Ques 1 ( D ) A They are denatured at temperatures above 60 oC. B They are inhibited at low pH values. C They catalyse the breakdown of large molecules into smaller ones. D They are required in small amounts.
- 36. 2 ml of amylase solution is added to 5ml of starch solution which is kept in a water bath maintained at 70 oC. Then the mixture is cooled down from 70 oC to 10oC. Which of the following shows the change in the reaction rate of this mixture ? Micro Ques 2 ( D )
- 37. An enzyme may be inactivated by ___________. Micro Ques 3 ( B ) A removing the products of the reaction as they appear B blocking its active site C halving the concentration of the enzyme D adding another metal as co-enzyme
- 38. MicroQuestion • Qn1: Enzymes speed up rate of reaction, Highly specific in their reaction. Remain chemically unchanged at end of reaction, hence they are required in small amount. The enzymes reaction can be affected by temperature and pH. • Qn2: It refers to the depression in the enzyme that substrate can fit it. • Qn3: Breakdown of complex molecules and build up of complex molecules from simples molecules.
- 39. !! Activity Time !! Each of you should get either a KEY or a LOCK
- 40. You have 5 mins to look for the key that opens your lock!
- 41. Lets Reflect! • What does the lock represent? • Enzyme • What does the key represent? • Substrate • Where is the active site? • In the lock
- 42. Issues with the Lock & Key Hypothesis The lock (enzyme) changes shape after the reaction *Enzymes are unchanged after the reaction The key (substrate) does not give rise to any new products *Substrates give rise to new products with the help of enzymes
- 43. Enzymes In conclusion, enzyme action is specific due to the shape of the substrate and active site being complementary to each other.
Editor's Notes
- http://glencoe.mheducation.com/sites/0078802849/student_view0/unit2/chapter6/virtual_labs.html# http://www.abpischools.org.uk/page/modules/enzymes/enzymes3.cfm?coSiteNavigation_allTopic=1 http://www.bbc.co.uk/schools/gcsebitesize/science/add_ocr_21c/life_processes/reactionsact.shtml
- An exothermic reaction is a chemical or physical reaction that releases heat. It gives out energy to its surroundings. The energy needed for the reaction to occur is less than the total energy released.
- An exothermic reaction is a chemical or physical reaction that releases heat. It gives out energy to its surroundings. The energy needed for the reaction to occur is less than the total energy released.