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Enzymes

Optimum. Substrate. Product. Temperature. Enzymes. Specific. pH. Unchanged. Protein. Catalyst. Active site. Metabolic reactions. Chemical reactions in a living cell. PRODUCT(S). SUBSTRATE(S). reaction. Normally too slow to sustain life. Catalysts speed up reactions.

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Enzymes

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  1. Optimum Substrate Product Temperature Enzymes Specific pH Unchanged Protein Catalyst Active site

  2. Metabolic reactions Chemical reactions in a living cell PRODUCT(S) SUBSTRATE(S) reaction Normally too slow to sustain life. Catalysts speed up reactions

  3. Metabolism Catabolic reactions break down molecules eg digestion • Anabolic reactions build up molecules eg photosynthesis

  4. Enzymes Enzymes are proteins which act as biological catalysts – they speed up biological reactions which otherwise would be too slow to sustain life Enzymes are unchanged by reaction Enzymes are usually Specific for a substrate or group of substrates (the chemicals they act on) Summary

  5. SUBSTRATE Enzyme-substrate complex Enzyme brings reactive parts of substrates together for reaction to occur ENZYME PRODUCT

  6. SUBSTRATE Enzyme brings reactive parts of substrate together for reaction to occur Enzyme-substrate complex Summary ENZYME PRODUCT

  7. Lock and Key model SUBSTRATE products enzyme Enzyme-SUBSTRATE complex http://www.youtube.com/watch?v=CZD5xsOKres&feature=related Enzyme will only bind substrates that fit exactly into the active site

  8. Induced fit model SUBSTRATE Substrate causes shape change in active site products http://www.5min.com/Video/Enzyme-Action-The-Induced-Fit-Model-150616169 (12 min) Enzyme-SUBSTRATE complex

  9. Theories of enzyme action COMPARE: In both models • an enzyme-substrate complex is formed • the activation energy is lowered • enzyme remains unchanged afterwards • substrate  products CONTRAST: In lock and key model substrate must fit active site exactly in order to bind, whereas with the induced fit model the substrate can cause active site to change slightly to allow a fit. Summary

  10. Denaturing proteins • Certain conditions permanently break bonds that hold the enzyme’s 3D shape. • Active site shape destroyed enzyme high temperature cannot function Summary

  11. Activation Energy Reactions require energy to get them going A To get the ball to B, you need to give it enough energy to get over the top – even though B is lower than A B

  12. Activation Energy Enzymes lower the activation energy required to start a reaction http://www.youtube.com/watch?v=VbIaK6PLrRM&feature=related (1 min) A Summary B

  13. MENU Quick Quiz Key Words Exercises MCQ Recap Videos Extra slides

  14. Key words Back to menu • Metabolism • Substrate • Product • Reaction rate • Enzyme • Globular protein • Biological catalyst • 3D structure • Denaturation • Active site • Specificity • Enzyme-substrate complex • Lock and Key model • Induced fit model • Exergonic • Endergonic • Activation energy

  15. Quick quiz Back to menu • Chemical reactions in living cells are _____ reactions • ____ reactions build up molecules • ____ reactions break down molecules • ____ speed up reactions • ____ are biological catalysts • Enzymes are made of ____ • Enzymes are ____-shaped • Enzyme function depends on its ____ • The ____ site of the enzyme binds with the substrate • ____ model: substrate must fit exactly into the enzyme • ____ model: enzyme shape can change to fit • Enzymes lower the ____ required to initiate a reaction Answers

  16. Quick quiz Back to menu • Chemical reactions in living cells are metabolic reactions • Anabolic reactions build up molecules • Catabolic reactions break down molecules • Catalysts speed up reactions • Enzymes are biological catalysts • Enzymes are made of protein • Enzymes are globular-shaped • Enzyme function depends on its shape • The active site of the enzyme binds with the substrate • Lock and keymodel: substrate must fit exactly into the enzyme • Induced fit model: enzyme shape can change to fit • Enzymes lower the activation energyrequired to initiate a reaction

  17. Exercise Back to menu • Workbook pp 50-1, qq15-17 • Pathfinder pp44-5 (or 50-51) qq 3-6 EXTRA READING • Pathfinder p48 (or p42) Proteins and Enzymes • Excellence in Biology p114-116 • Booklet p3

  18. Videos Back to menu http://www.youtube.com/watch?v=E90D4BmaVJM&feature=related (10 min, includes biotechnology) http://www.youtube.com/watch?v=MUtfF2qnzGo&feature=related (metabolism1, 6 min) http://www.youtube.com/watch?v=AEsQxzeAry8&feature=related (digestion by enzymes, 3min)

  19. Question 1 34 Back to menu High temperatures damage proteins by (a) decomposing them (b) changing their chemical composition √ (c) changing their shape (d) making them soluble

  20. 35 Question 2 Back to menu A protein is made up of a series of (a) glucose units (b) fatty acids √ (c) amino acids (d) carbohydrates

  21. 37 Question 3 Back to menu Enzymes are √ (a) proteins (b) lipids (c) carbohydrates (d) a combination of these

  22. 38 Question 4 Back to menu An enzyme can (a) change a reaction (b) prevent a reaction (c) slow down a reaction √ (d) speed up a reaction

  23. Question 5 39 Back to menu A substrate is a substance which √ (a) an enzyme acts on (b) is produced by an enzyme reaction (c) is a particular kind of enzyme (d) is any chemical substance in a cell

  24. 40 Question 6 Back to menu An enzyme can (a) combine with different substrates (b) form different kinds of end-product (c) function at temperatures above 90oC √ (d)lower the activation energy needed for a reaction

  25. 41 Question 7 Back to menu The part of an enzyme which combines with the substrate is called: (a) the reaction centre √ (b) the active site (c) the action centre (d) the reaction site

  26. Question 8 42 Back to menu After being exposed to a high temperature an enzyme cannot function because..... (a) it has been broken down √ (b) its shape has been changed (c) its composition has been changed (d) it cannot separate from its substrate

  27. ANSWER 43 Back to menu Correct √ click arrow to return

  28. 44 ANSWER Back to menu IncorrectX click arrow to return Oooops!

  29. RECAP Back to Menu Past Papers 2006-2009 Q2 Your choice Highlight key ideas in your workbook Copy diagrams from Workbook p50 or Pathfinder p42 Summarise the notes on enzymes from workbook & pathfinder Add key words and definitions to your glossary

  30. 3-dimensional enzyme structure Globular proteins – long polypeptides held in shape by various bonds between side groups (eg hydrogen and ionic bonds) to form globules (ball-shaped) Polypeptide = chain of amino acids Back to Menu

  31. Back to Menu Lock and Key Model products SUBSTRATE enzyme enzyme Enzyme-SUBSTRATE complex

  32. Back to Menu Induced Fit Model SUBSTRATE products enzyme enzyme Enzyme-SUBSTRATE complex

  33. Exergonic reactions Back to Menu Substrates have more energy than the products ENERGY REACTION eg respiration breaks down sugar to release energy

  34. Endergonic reactions Back to Menu Substrates have less energy than the products ENERGY REACTION eg photosynthesis uses solar energy to make sugar

  35. Exergonic Energy released by reaction Endergonic Energy used by reaction Activation energy Activation energy Free energy  Free energy  Nett energy released by reaction Nett energy used by reaction Time  Time  Back to Menu

  36. Back to menu The end……………………….

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