Cells And Enzymes


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Cells And Enzymes

  1. 1. 2.1 Catalysts <ul><li>Today’s Learning Objectives: </li></ul><ul><li>Name the breakdown products of hydrogen </li></ul><ul><li>peroxide </li></ul><ul><li>Describe the effect of a catalyst on speed of </li></ul><ul><li>chemical reactions. </li></ul><ul><li>Three properties of a catalyst. </li></ul><ul><li>The general term for a biological catalyst. </li></ul><ul><li>Where enzymes are found. </li></ul><ul><li>Word equation for the reaction catalysed by the </li></ul><ul><li>enzyme catalase. </li></ul>
  2. 2. A catalyst is a substance which speeds up chemical reactions without being changed by the reaction. <ul><li>When a catalyst is present, less energy is needed to start a chemical reaction </li></ul><ul><li>When a catalyst is present, the speed of the chemical reaction is faster </li></ul><ul><li>The catalyst remains unchanged at the end of the reaction </li></ul>e.g. Hydrogen peroxide Water + Oxygen Manganese Dioxide Catalyst
  3. 3. An enzyme is a biological catalyst. Enzymes are found in all living cells. Catalase is an enzyme which causes the breakdown of hydrogen peroxide Hydrogen peroxide Water + Oxygen Catalase Enzyme
  4. 4. 2.2 Nature of Enzymes <ul><li>Today’s Learning Objectives: </li></ul><ul><li>The type of chemical enzymes are composed of. </li></ul><ul><li>Define the term substrate when thinking about </li></ul><ul><li>enzymes. </li></ul><ul><li>State the meaning of the term ‘specific’ when </li></ul><ul><li>thinking about enzymes </li></ul><ul><li>Describe the active site of an enzyme. </li></ul><ul><li>Explain the term complementary when applied to </li></ul><ul><li>active sites. </li></ul><ul><li>Explain the term specificity when describing an </li></ul><ul><li>enzyme and it’s active site. </li></ul>
  5. 5. <ul><li>There are thousands of different enzymes….why? </li></ul><ul><li>Each enzyme has it’s own unique protein structure </li></ul><ul><li>and shape which matches a specific substrate </li></ul><ul><li>Each enzyme, therefore, has it’s own substrate </li></ul><ul><li>that no other enzymes can work on </li></ul>Substrate Enzyme Product
  6. 6. Enzyme action is said to be specific. That means an enzyme can only work on one specific substrate Hydrogen peroxide Water + Oxygen Catalase Hydrogen peroxide Amylase
  7. 7. Lock and Key Idea The active site of an enzyme is the place on its surface which is complementary in shape to it’s substrate Substrate e.g. Hydrogen Peroxide Enzyme e.g. Catalase Active sites
  8. 8. Enzyme activity Animations-click to view
  9. 9. 2.3 Breakdown Reactions <ul><li>Today’s Learning Objectives: </li></ul><ul><li>Define the term breakdown reaction </li></ul><ul><li>State the reason for breakdown of starch by animals </li></ul><ul><li>Name the substrates and products of the enzyme amylase </li></ul><ul><li>Describe a test for starch </li></ul><ul><li>Describe a test for maltose sugar </li></ul><ul><li>Explain the need for a control in an investigation </li></ul>
  10. 10. A BREAKDOWN reaction is one in which an ENZYME breaks down it’s substrate into SMALLER molecules. Starch is an energy rich compound which must be broken down into smaller molecules to be absorbed into the blood stream. An enzyme called AMYLASE (found in saliva) is the first stage of this breakdown. Starch Maltose Amylase Enzyme
  11. 11. Carbohydrates G G G G G G Starch (insoluble) G G G G Maltose Amylase action
  12. 12. Iodine Testing for Starch Benedicts Testing for Maltose + - + -
  13. 13. 2.4 Synthesis Reactions <ul><li>Today’s Learning Objectives: </li></ul><ul><li>Define the term synthesis reaction </li></ul><ul><li>Name the substrate and product of the enzyme phosphorylase </li></ul><ul><li>Using the term diffusion, explain why plants store starch instead of glucose </li></ul><ul><li>Describe a phosphorylase experiment and it’s controls </li></ul><ul><li>Explain what storage molecules are and why organisms synthesise them </li></ul><ul><li>Explain what structural molecules are and why organisms synthesise them </li></ul>
  14. 14. Starch Storage in Potato Plants Glucose converted to glucose-1-phosphate Some glucose transported to roots Some glucose used for energy by shoots and young leaves or stored in fruit Glucose is made in leaves by photosynthesis An enzyme called Phosphorylase joins these molecules to produce STARCH
  15. 15. Phosphorylase is an enzyme which SYNTHESISES starch In a synthesis reaction the substrate molecules are built up into larger molecules Glucose-1-phosphate Starch Phosphorylase
  16. 16. Starch Synthesis Experiment Row A Substrate + enzyme Row B Substrate + water Row C Enzyme + Water 5 min 10 min 15 min 20 min Iodine added
  17. 17. 2.5 Enzymes and Temperature <ul><li>Today’s Learning Objectives: </li></ul><ul><li>Describe the effect of increasing temperature on enzyme-catalysed reactions </li></ul><ul><li>Draw and interpret a line graph showing the effect of temperature on enzyme activity </li></ul><ul><li>Define the term optimum temperature </li></ul><ul><li>State the optimum temperature for enzyme reactions in the human body </li></ul><ul><li>Describe the effect of high temperature on protein structure </li></ul><ul><li>Define the term denatured </li></ul>
  18. 18. The OPTIMUM temperature for an enzyme is the temperature at which it works best . The optimum temperature for most human enzymes is: 37°C = body temperature
  19. 19. Enzyme activity Denaturing-click to view A DENATURED enzyme is an enzyme that has lost its natural structure permanently and no longer works. Remember ! An enzyme is NEVER dead , dying or killed !!!!!!
  20. 20. 2.6 Enzymes and pH <ul><li>Today’s Learning Objectives: </li></ul><ul><li>Describe the pH scale </li></ul><ul><li>State the pH levels of the mouth, stomach and small intestines </li></ul><ul><li>Define the term optimum pH </li></ul><ul><li>Interpret data to identify the optimum pH for an enzyme </li></ul><ul><li>State the optimum pH for pepsin </li></ul><ul><li>State the optimum pH for trypsin </li></ul><ul><li>Describe the colour change of Clinistix when exposed to glucose </li></ul><ul><li>Name the substrate and products of the enzyme invertase </li></ul>
  21. 21. The pH Scale Neutral Acidic Alkali Stomach pH 2 Mouth pH 7 Small Intestine pH 9
  22. 22. How do changes in pH affect this breakdown reaction? Invertase G F Sucrose G F Glucose Fructose (substrate) (products)
  23. 23. The OPTIMUM pH for an enzyme is the pH at which it works best . Each enzyme of the digestive system has a different optimum pH depending on its site of action.
  24. 24. 2.7 Writing up an Investigation <ul><li>Today’s Learning Objectives: </li></ul><ul><li>Write the aim of an investigation </li></ul><ul><li>Identify the altered variable and the measured variable in an investigation </li></ul><ul><li>Identify variables which need to be controlled </li></ul><ul><li>Record the results in a suitable table </li></ul><ul><li>Draw a suitable graph of results obtained in an experiment </li></ul><ul><li>Draw an appropriate conclusion based on results </li></ul><ul><li>Identify features of an investigation which should be evaluated </li></ul>