Mr Exham IGCSE Biology - Enzymes

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This covers the enzyme section of Edexcel IGCSE Biology course section 1.1 Life processes

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Mr Exham IGCSE Biology - Enzymes

  1. 1. IGCSE Biology Brought to you by mrexham.com Copyright©2015HenryExham MAKING SENSE OF Topic 1.1 Life Processes Enzymes
  2. 2. Copyright © 2015 Henry Exham • Can you explain the role of enzymes as biological catalysts and how they are used in metabolic reactions? • How can enzyme function be affected by temperature? • Can you describe a simple controlled experiment to show how enzyme activity is affected by temperature? • How are enzymes affected by pH? (Separate science only) 1.1 Life Processes - Enzymes Objectives 2
  3. 3. Copyright © 2015 Henry Exham • All chemical reactions that happen in a cell are controlled by enzymes. • Enzymes are biological catalysts. • This means they speed up the reaction and do not get used up in the reaction. • They are all proteins which are coded for by genes. • The function of enzymes is to catalyse metabolic reactions. 3 1.1 Life Processes - Enzymes What are enzymes?
  4. 4. Copyright © 2015 Henry Exham 4 1.1 Life Processes - Enzymes What are enzymes? • Our body temperature is 37oC • This is quite a low temperature for reactions to take place. • Without enzymes the reactions in our bodies would occur too slowly to support our body’s needs.
  5. 5. Copyright © 2015 Henry Exham 5 1.1 Life Processes - Enzymes How do enzymes work? • Each enzyme has an active site. • The molecule that it wants to help change is called the substrate. • The active site fits the substrate like a lock and a key. SubstrateActive site
  6. 6. Copyright © 2015 Henry Exham 6 1.1 Life Processes - Enzymes How do enzymes work? Substrate enters active site1
  7. 7. Copyright © 2015 Henry Exham 7 1.1 Life Processes - Enzymes How do enzymes work? Substrate enters active site An enzyme-substrate complex forms1 2
  8. 8. Copyright © 2015 Henry Exham 8 1.1 Life Processes - Enzymes How do enzymes work? Substrate enters active site1 2 3
  9. 9. Copyright © 2015 Henry Exham 9 1.1 Life Processes - Enzymes How do enzymes work? Products form and leave active site Reaction occurs Substrate enters active site An enzyme-substrate complex forms1 2 34
  10. 10. Copyright © 2015 Henry Exham 10 1.1 Life Processes - Enzymes Factors affecting enzymes • Each enzyme has an optimum temperature at which it works best. • Above this temp the shape of the enzyme’s active site is changed by the heat. • The enzyme becomes DENATURED and stops working. 0 1 0 2 0 3 0 4 0 5 0 6 0 7 0 Temperature (oC) Rateofreaction
  11. 11. Copyright © 2015 Henry Exham 11 1.1 Life Processes - Enzymes Factors affecting enzymes • The optimum pH for most enzymes is pH 7. • Although enzymes in the stomach can work at pH 2. pH 5 6 7 8 9 Rateofreaction This slide is for separate science only
  12. 12. Copyright © 2015 Henry Exham 12 1.1 Life Processes - Enzymes Factors affecting enzymes Can you describe a simple controlled experiment to show how enzyme activity is affected by temperature? • Amylase is a good enzyme to investigate. • It is used in digestion to breakdown the starch you eat into sugar. • You can test for starch using iodine. • If there is starch present the solution will change colour from the initial brown/yellow colour to blue/black.
  13. 13. Copyright © 2015 Henry Exham 13 1.1 Life Processes - Enzymes Factors affecting enzymes
  14. 14. Copyright © 2015 Henry Exham 14 1.1 Life Processes - Enzymes Factors affecting enzymes
  15. 15. Copyright © 2015 Henry Exham 15 1.1 Life Processes - Enzymes Factors affecting enzymes • Choose five temperatures to investigate in the range of 10oC to 80oC. • Repeat the same procedure for each temperature making sure that all other variables are kept constant between each experiment. • For a control experiment you could use boiled amylase instead of normal amylase. • To make the experiment more reliable repeat each temperature 3 - 5 times and take the average time. • Plot the results as a graph of temperature on the x-axis against time on the y-axis.
  16. 16. This PowerPoint is protected under copyright. It is designed for educational use. Either personal study or to be presented to a class. It may be edited or duplicated for these purposes only. It must not be shared or distributed online in any format. Some images used are under a separate creative commons license, these are clearly marked. Copyright © 2015 Henry Exham Brought to you by MrExham.com TERMS AND CONDITIONS 16
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