Enzymes

1. Enzymes And how they work

2. Enzymes • Enzymes are proteins – they are biological catalysts.

3. Enzymes • Enzymes are proteins – they are biological catalysts. • This means they can speed up a reaction that would otherwise take months to occur while the enzyme itself is NOT CHANGED in the process.

4. Enzymes • Enzymes are proteins – they are biological catalysts. • This means they can speed up a reaction that would otherwise take months to occur while the enzyme itself is NOT CHANGED in the process. • Enzymes can therefore be used over and over again.

5. Enzymes • Enzymes are proteins – they are biological catalysts. • This means they can speed up a reaction that would otherwise take months to occur while the enzyme itself is NOT CHANGED in the process. • Enzymes can therefore be used over and over again.

6. Lock & Key model • Two enzymes of different shapes working together to fit into a reactive site.

7. Lock & Key model • Two enzymes of different shapes working together to fit into a reactive site. • When they fit together, an enzyme-substrate complex is formed and the two chemicals react.

8. Lock & Key model • Two enzymes of different shapes working together to fit into a reactive site. • When they fit together, an enzyme-substrate complex is formed and the two chemicals react joining together. • The enzyme then detaches itself and is ready to catalyse another two chemicals that fit. • ** Catalysts must be specific – eg they can only fit together, not to other ones… • http://www.youtube.com/watch?v=EiMBsgNZh-M

9. Induced fit model • Substrate binds to the enzyme, may induce a change in the shape of the enzyme molecules.

10. Induced fit model • Substrate binds to the enzyme, may induce a change in the shape of the enzyme molecules. • The change puts strain on the chemical bonds between the substrate molecules and causes them to react. • http://www.youtube.com/watch?v=z8lG8X9ZvxQ&feature=related

11. Induced fit model • Substrate binds to the enzyme, may induce a change in the shape of the enzyme molecules. • The change puts strain on the chemical bonds between the substrate molecules and causes them to react. • When the product is released, the enzyme returns to its original shape.

12. Activation energy barrier • Energy is needed to get the reaction going – this is activation energy barrier.

13. Activation energy barrier • Energy is needed to get the reaction going – this is activation energy barrier. • In a lab, you could use heat to speed up the reaction, but in your body, you can’t heat it up = enzymes.

14. Activation energy barrier • Energy is needed to get the reaction going – this is activation energy barrier. • In a lab, you could use heat to speed up the reaction, but in your body, you can’t heat it up = enzymes. • Enzymes are used to lower the activation energy barrier which allows molecules of relatively low energy to react.

15. Types of enzymes • Pepsin – breaks down protein in the stomach and works well in acidic conditions.

16. Types of enzymes • Pepsin – breaks down protein in the stomach and works well in acidic conditions. • Amylase – saliva enzyme which breaks down starch.

17. Factors affecting enzymes • Heat – ezymes catalyse a reaction faster if the temperature is up to 40-45 degrees. Above that, the enzyme denatures and can no longer cause a reaction.

18. Factors affecting enzymes • Heat – ezymes catalyse a reaction faster if the temperature is up to 40-45 degrees. Above that, the enzyme denatures and can no longer cause a reaction. • pH (acidity) – Each enzyme has a range of pH which is it’s optimal pH level = works the fastest.

19. Factors affecting enzymes • Heat – ezymes catalyse a reaction faster if the temperature is up to 40-45 degrees. Above that, the enzyme denatures and can no longer cause a reaction. • pH (acidity) – Each enzyme has a range of pH which is it’s optimal pH level = works the fastest. • Concentration – enzymes act faster if the substrate or the enzyme is increased.

20. Factors affecting enzymes • Heat – ezymes catalyse a reaction faster if the temperature is up to 40-45 degrees. Above that, the enzyme denatures and can no longer cause a reaction. • pH (acidity) – Each enzyme has a range of pH which is it’s optimal pH level = works the fastest. • Concentration – enzymes act faster if the substrate or the enzyme is increased. • Chemicals – heavy metal ions such as lead and mercury can slow down or even stop enzyme activity.

21. Factors affecting enzymes • Heat – ezymes catalyse a reaction faster if the temperature is up to 40-45 degrees. Above that, the enzyme denatures and can no longer cause a reaction. • pH (acidity) – Each enzyme has a range of pH which is it’s optimal pH level = works the fastest. • Concentration – enzymes act faster if the substrate or the enzyme is increased. • Chemicals – heavy metal ions such as lead and mercury can slow down or even stop enzyme activity.

22. Questions • Explain why enzymes are not destroyed by the reactions they catalyse. • The production of C02 by yeast cells during fermentation increases as the temp of the yeast culture is raised from 30 – 40 degrees C. Explain why this increase in production could not continue if the temperature were raised further. • Suggest a reason why life would be impossible without enzymes. • A piece of fish flesh was placed in a sample of liquid in a test tube taken from a cat’s stomach. It was incubated at 37 degrees. What effect would shaking the test tube sample have on the piece of fish flesh?