3. What is an enzyme? Enzyme actions Lock and key hypothesis Effect of temperature on enzyme action Effect of pH on enzyme action Uses of enzymes in daily life

4. protein a catalyst: speeds up chemical reactions in the body no change after a reaction a little amount is enough specific works within a narrow range of pH and temperature What is an enzyme? can be reused

5. Enzyme action: catabolic action enzyme-substrate complex products enzyme can be reused again substrate

6. Enzyme action: anabolic action enzyme can be reused again substrates productenzyme-substrate complex

7. Lock and key hypothesis specificityExplains the specificity of enzyme actions Each key opens only one lock Each enzyme acts on one or a few substrates that fits into its active site

8. Lock and key hypothesis key = enzyme lock = substrate lock and key = enzyme-substrate complex key has no change lock is open

9. Effect of temperature on enzyme action Works slowly at low temperature (inactive) Does not work at high temperature (denatured) Works best at a narrow range of temperature (optimum temperature)

10. Enzyme activity increases with a rise in temperature It then decreases with a further increase in temperature. Effect of temperature on enzyme action Temperature ( o C) Rate ofenzymeaction(arbitraryunit) The optimum temperature is about 40 o C for most enzymes in human body. until it reaches a maximum (the optimum temperature).

11. Enzyme activity increases with pH until a maximum (the optimum pH), then decreases as pH increases. pH Rate ofenzymeaction(arbitraryunit) Different enzymes have their own optimum pH. Effect of pH on enzyme action

12. washing powder cleaning solution of contact lens meat tenderizers Uses of enzymes in daily life

13. Enzymes are special proteins that speed up chemical reactions inside organisms (a biological catalyst) take part in both catabolic and anabolic reactions are specific whose specificity explained by lock and key hypothesis whose activity changes with temperature and pH Summary