1. Enzymes

2. Guest Publication Round: Featuring guest publication “EMT”

3. Stimulation of novel thermostable extracellular lipolytic in cultures of Thermus species.

4. Stimulation of novel thermostable extracellular lipolytic enzymes in cultures of Thermus species.

5. Bacterial biofilm removal using fungal

6. Bacterial biofilm removal using fungal enzymes

7. Novel method of stabilization on crosslinked thermosensitive carriers

8. Novel method of enzyme stabilization on crosslinked thermosensitive carriers

9. Study of the effects of temperature, pH and NaCl, on the proteolytic and lipolytic activities of -related lactic acid bacteria by quadratic response surface methodology

10. Study of the effects of temperature, pH and NaCl, on the proteolytic and lipolytic activities of cheese-related lactic acid bacteria by quadratic response surface methodology

11. Lesson objectives What are enzymes? Why enzymes are important The structure of enzymes How enzymes work The effects of change in temperature, pH, substrate concentration, and competitive and non-competitive inhibition on the rate of enzyme action.

12. What are enzymes? Biological catalyst Globular protein Speeds up the rates of many chemical reactions, e.g. respiration, condensation reactions, hydrolysis reactions The thing they ‘work on’ is called the substrate

13. Why are enzymes important? Enzymes lower the activation energy of a reaction (the minimum amount of energy needed for a reaction to start) This means chemical reactions can happen in the body at low temperatures Get rid of toxic products quickly in our body

14. Structure of Enzymes

15. How enzymes work Lock and Key hypothesis: Enzyme and substrate have complementary shapes and fit together exactly Induced-fit hypothesis: Enzyme and substrate have a nearly complementary shape, and the active site changes shape to fit around the substrate

17. Effect of temperature on enzyme activity

18. Effect of pH on enzyme activity

19. Effect of substrate concentration on enzyme activity

20. Competitive inhibitors

21. Non-competitive inhibitors

22. Graph page 36

23. For your exam you need to know… Enzymes are proteins Enzymes as catalysts lowering activation energy through the formation of enzyme-substrate complexes. The lock and key and induced fit models of enzyme action. The properties of enzymes relating to their tertiary structure. Description and explanation of the effects of temperature, competitive and non-competitive inhibitors, pH and substrate concentration. Use the lock and key model to explain the properties of enzymes. They should also recognise its limitations and be able to explain why the induced fit model provides a better explanation of specific enzyme properties.

24. Urease is an enzyme which converts urea into ammonia. The effect of urea concentration on the rate of reaction of urease was investigated. Curve A on the graph shows these results. The investigation was then repeated with thiourea present. Thiourea is an inhibitor of urease. Curve B on the graph shows these results. Explain the shape of curve A. (2)

25. Increase in rate of reaction: As more collisions between enzyme and substrate / more enzyme –substrate complexes form / substrate (concentration) limits rate of reaction; No further change in rate: As all active sites occupied / saturated / enzyme limiting rate of reaction; (reject enzymes used up)

26. Explain how thiourea inhibits urease, using evidence from the graph to support your answer. (4 marks)

27. Inhibitor attaches to enzyme; Changes (shape of) enzyme / active site / 3D structure / tertiary structure or fewer active sites available; Substrate no longer able to bind / less chance of binding / less E-S complexes formed; Graph shows effect is not removed by excess substrate; 4 marks

28. The rate of reaction was determined by measuring the change in pH. The temperature was kept constant in all the reaction tubes. Give one other factor which should be kept constant. Explain your answer. Factor.............................................................................. Reason............................................................................................................................... (2 marks)

29. Urease (enzyme) / inhibitor concentration / volume / amount; If number of active sites / enzymes changes, rate of reaction / number of collisions / number of E-S complexes formed will change;

30. Explain how the shape of an enzyme molecule is related to its function. 3 marks

31. specific 3D tertiary structure/shape; substrate complementary shape; (reject same shape) substrate (can bind) to active site/ can fit into each active site;

32. Bacteria produce enzymes which cause food to decay. Explain how vinegar, which is acidic, can prevent the action of bacterial enzymes in some preserved foods. 3 marks

33. (bacterial) active site/enzymes/proteins denatured / tertiary 3D structure disrupted/changed; (ionic) bonds broken; (reject peptide bonds) (ignore other bonds) no enzyme substrate complex formed / substrate no longer fits;