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Effect of Temperature on Enzyme Activity

This lesson explores the factors affecting enzyme activity and focuses on the effect of temperature. Students will learn about optimum conditions, denaturation, and conduct experiments to observe the effect of temperature on enzymes. The lesson includes graph interpretation and emphasizes the concept of enzyme denaturation at high temperatures.

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Effect of Temperature on Enzyme Activity

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  1. Unit 1: Cell Biology Key Area 1: Proteins KA1.3c: Enzymes Factors effecting enzyme activity.Part 1: Temperature National 5 Biology Mrs Smith - National 5 Biology

  2. Lesson Starter Chemically what are enzymes? Which two words summaries the function of enzymes? What part do enzymes play in reactions. How are enzymes altered by the reactions in which they take part? What are the 2 types of enzyme reactions? Mrs Smith - National 5 Biology

  3. Learning Intentions • In today’s lesson you will be learning about how temperature effects enzymes activity. • By the end of this lesson you should aim to: • By the end of this lesson you should aim to: • Understand the terms optimum, working range and denatured. • Understand what effect temp has on enzyme activity and describe experiments to show this. • Graph interpretation (numeracy outcome) Mrs Smith - National 5 Biology

  4. Enzyme activity introduction. • Enzymes and other proteins are most active when given optimum conditions. • This means that if an enzyme is given an optimal set of conditions the maximum reaction rate will occur. Mrs Smith - National 5 Biology

  5. Factors affecting enzyme activity The factors that affect enzyme activity are. • Substrate concentration • Enzyme concentration • Temperature • PH . To function efficiently an enzyme (or other proteins) require a suitable temperature and pH. There will be a working range of pH's or temperatures that the enzyme will work at. However the pH or temperatue where the enzyme is most active is called the OPTIMUM. For National 5 you only need to understand about temperature and pH Mrs Smith - National 5 Biology

  6. Effect of temperature • This graph summarises the general effect of temperature on enzyme activity. • At very low temps, enzyme molecules are inactive but undamaged. • A low temps, enzyme and substrate move around slowly in their surrounding medium. They meet only rarely, and the rate of the reaction remains low. • As the temp increases, the two type of molecule move about at a faster rate and the rate of the reaction increases. Mrs Smith - National 5 Biology

  7. Optimum temperature • This graph summarises the general effect of temperature on enzyme activity. • The temp at which most enzyme-substrates molecular activity occurs (without any damage taking place) is a value within the range of 35-40oC. • This temp at which the reaction works best is called the enzyme’s optimum temperature. Mrs Smith - National 5 Biology

  8.          The optimum value is the condition in which the enzyme is most active "Working at its maximum rate" The optimum value in the graph shown is 37oC Mrs Smith - National 5 Biology

  9. Denaturation • At temps above 40oC, an enzyme’s atoms vibrate so much that some of the chemical bonds holding its amino acids together break and the molecule begins to come apart. Mrs Smith - National 5 Biology

  10. Denaturation Because the bonds holing amono acids together are broken the shape of the active site becomes altered and the enzyme is unable to fit with its substrate. An enzymes damaged state is said to  be denatured this will affect the rate of reaction. Once denatured an enzyme is permanently inactive. Mrs Smith - National 5 Biology

  11. What happens to an egg white when cooked? • Egg white is made of a protein called albumin. • When raw egg white is heated, the albumin coagulated and changes from a colourless liquid to a white solid. • On cooling the egg white does not return to its original state. Its molecular structure has been altered irreversibly (denatured). Mrs Smith - National 5 Biology

  12. TASK: EXPERIMENT -Effect of temperature on catalase activity and egg white Teacher demo water Oxygen bubble Egg albumen (egg white) Hydrogen peroxide Liver (containing catalase) heat As the temperature increases from just above freezing the rate of bubble production increases until around 40oC - the optimum temperature for catalase. Above 40oC rate of bubble production begins to fall. Around this temperature the egg albumen which is pure protein begins to solidify showing that the protein is denatured. Mrs Smith - National 5 Biology

  13. Investigating the effect of temp on amylase activity. Mrs Smith - National 5 Biology

  14. Investigating the effect of temp on amylase activity. Mrs Smith - National 5 Biology

  15. Denaturation • This graph summarises the general effect of temperature on enzyme activity. • Beyond 40oc, as more molecules of enzyme become denatured and inactive, the rate of the reaction decreases rapidly. At temperatures of about 55-60oC. Enzyme activity has often found to have come to a complete halt. This is because ALL the enzyme molecules have become denatured. Mrs Smith - National 5 Biology

  16. Describing and explaining graphs axis labels number Top Tip - You must mention both _____ ______and a _______ each time you describe a section of graph. Part A described - As the temperature increases to 37oC the enzyme reaction rate increases rapidly. Part A explained - As temperature increases the substrate moves more quickly and is processed faster. Part B described- As the temperature increases above 37oC the enzyme reaction rate decreases rapidly. Part B explained - As the temperature increases above 37oC the enzyme structure is destroyed i.e. it is denatured. Mrs Smith - National 5 Biology

  17. TASK: Factors affecting enzymes -Temperature At low temperature enzymes areinactive. As the temperature increases enzyme activity increases. The temperature at which an enzyme is most active is known as its _________ temperature.   optimum Amylase (an enzyme) found in humans and has an optimum temperature of 37°C - the same as the human body temp. At high temperature (above 45°C) enzymes are __________ – this means they are permanently damaged and will no longer work. denatured Mrs Smith - National 5 Biology

  18. Unit 1: Cell Biology Key Area 1: Proteins KA1.3c: Enzymes Factors effecting enzyme activity.Part 2: pH National 5 Biology Mrs Smith - National 5 Biology

  19. Learning Intentions • In today’s lesson you will be learning about how pH effects enzymes activity. • By the end of this lesson you should aim to: • Describe the effect of pH on enzymes • Complete a problem-solving exercise to determine the above effect (numeracy outcome) • Finish your catalase write-up/ practise questions Mrs Smith - National 5 Biology

  20. Lesson Starter [WITHOUT LOOKING BACK!] Describe the meaning of optimum and denatured(with reference to enzymes) Describe the effect of temperature on enzymes Mrs Smith - National 5 Biology

  21. Factors affecting enzymes - pH pH is a measure of how acid or alkaline a solution is • All enzymes are affected by pH. • Each enzyme has a specific pH • Each enzyme has a pH range where they work -outside of this range it will not work at all. Mrs Smith - National 5 Biology

  22. Optimum pH • Each enzyme is found to work best at a particular pH (its optimum pH). • Most enzymes function within a working pH range of about 5-9 with an optimum pH of around pH 7. • However there are exceptions. • Pepsin works best in strongly acidic conditions of pH 2.5 • Phosphatase  (plays a role in bone formation) works best at pH 10. Mrs Smith - National 5 Biology

  23. Experiment 1 : Demonstrating pH affects Pepsin activity – showing optimum pH Use the results on the handout of the egg albumen/ pepsin experiment to fill in the table below and draw a line graph to be able to work out the effect of pH on the enzyme Pepsin. What is the optimum pH for pepsin action? Why is this an advantage? Mrs Smith - National 5 Biology

  24. Experiment 2 : Demonstrating pH affects Pepsin activity Mrs Smith - National 5 Biology

  25. Experiment 3 : Demonstrating the effect of pH on catalase activity – showing optimum pH Each tube contains hydrogen peroxide with its pH adjusted from  6 to 12. Mrs Smith - National 5 Biology

  26. Questions in your groups discuss. • What would we expect to happen when the liver is added to hydrogen peroxide? (Think we have done this before). • What is our VARIABLE factor? • Why is it important to have the liver pieces of equal size? • Washing up liquid is also added to each cylinder – why would we use this? • How could we measure which pH was the best for the enzyme? Mrs Smith - National 5 Biology

  27. Task 5 minutes. Answers on SMB’s!! Mrs Smith - National 5 Biology

  28. Results: Tabulate and Graph! Mrs Smith - National 5 Biology

  29. Discussion & ConclusionEffect of pH on enzymes (Catalyse). • Remember liver contains the enzyme catalyse which promotes the breakdown of hydrogen peroxide to water + oxygen. • As oxygen is released froth is produced. • The height of the froth indicates the activity of the enzyme at each pH. From the results it can be seen that catalase is more active at around pH9 but works fairly well over a range of ph 7-11 (WORKING RANGE). Catalase does not work well outside this range. Mrs Smith - National 5 Biology

  30. Extreme pH’s can denature proteins too! • Egg white is made of a protein called albumin. • When raw egg white is added to strong acid the albumin coagulated and changes from a colourless liquid to a white solid. • When the pH is returned to neutral the egg white does not return to its original state. • Its molecular structure has been altered irreversibly (denatured). Mrs Smith - National 5 Biology

  31. TASK: Copy & complete the table below using information from the graph. Mrs Smith - National 5 Biology

  32. http://www.youtube.com/watch?v=D2j2KGwJXJc#t=29

  33. Have we achieved our Learning Intentions? • Check off your Learning Outcomes for today’s lesson: • The conditions under which an enzyme is most active is known as the optimumconditionsfor that enzyme. • Enzymes are denatured by high temperatures or high or low pHs. • When an enzyme is denatured its shape is changed so that it can no longer lock on to its substrate and catalyse its specific reaction. Mrs Smith - National 5 Biology

  34. Enzyme Bingo 8 catalase synthesis 2 substrate product specific optimum biological catalyst degradation phosphorylase lock and key range denatured pH

  35. http://www.youtube.com/watch?v=smtCH5HX44o

  36. Try this tutorial at home • http://highered.mheducation.com/sites/dl/free/0072495855/291136/enzymes.swf • Does need adobe flash Mrs Smith - National 5 Biology

  37. Mr W’s Enzyme song https://www.youtube.com/watch?v=NdMVRL4oaUo Mrs Smith - National 5 Biology

  38. TYK2 :Qu’s 1-4Torrance 1st edition pg42Torrance 2nd edition pg30 Mrs Smith - National 5 Biology

  39. TYK:How did you do? Mrs Smith - National 5 Biology

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