How are enzyme activities affected by temperature and pH ?

1. How are enzyme activities affected by temperature and pH ? 1 Temperature  Enzyme activity is usually expressed in terms ofreaction rate. • the rate at whichsubstrates are used up or broken down,or the rate offormation of product(s) • increase to a maximumand thendecrease as the temperature increases

2. At low temperatures:  Enzymes may beinactiveand the reaction rate islow. As the temperature rises:  Substrate and enzyme molecules havemore kinetic energyand vibrate more rapidly. enzyme activity temperature

3.  The chance of hitting each other to forman enzyme-substrate complexincreases, thus have ahigher reaction rate.  The reaction rate is the highest at theoptimum temperature. enzyme activity temperature 0 40 ℃ This enzyme works best at 40 ℃ !

4.  When the temperature isabove the optimum, shapesof enzymemolecules begin tochange.  Denaturation of enzyme enzyme activity  Enzyme loses its function andenzyme activity drops! temperature 40 ℃

5. 2 pH  Enzymes usually work within anarrow range of pH. Enzyme activity pH 2 4 6 8 10 12 14  Becausechange in pHvalue alsochanges the shapeof an enzyme.

6.  Enzymes work best at theiroptimum pH. pepsin salivary amylase • Optimum pH for pepsin is __. 2 • Optimum pH for salivary amylase is __. Enzyme activity 7 pancreatic lipase • Optimum pH for pancreatic lipase is ___. 10 pH 2 4 6 8 10 12 14  A great change in pH can causedenaturation.

7. Applications of enzymes  Proteaseare added to some washing powders to help in cleaning. An enzyme to digestproteins. Why proteases are added ??

8. Applications of enzymes  Papain from plants like papayas are added to meat tenderizers to soften meat. What is papain?? It is an enzyme!! (Remember that?)

9. Applications of enzymes  Some contact lens cleaners contain proteases to remove proteins.

10. Applications of enzymes  Cellulase is used to produce stonewashed jeans. What is cellulase? Is it an enzyme? Cellulase is an enzyme to digest cellulose!

11. Design a fair test to compare the enzyme activities of two biological washing powders. Discuss with your group members and present your ideas on the following items: • The method used to solve the problem. (Use labelled diagrams to illustrate the procedures!). • The way by which experimental results is collected. • The independent, dependent and controlled variables of this investigation.

12. Investigation of protease activities in different fruit juices Procedures: 1Heat the end of a cork borer in a Bunsen flame and allow it to cool. 2Gentlypress the borer down into the milk-agar to make 5 wells. Replace the lid quickly. 3Make amark on the plate to indicate the arrangement of samples.

13. Investigation of protease activities in different fruit juices 4 Use a clean dropper to fill up each wells with pineapple juice, Kiwi fruit juice, papaya juice, pineapple juice and distilled water. different fruit juices distilled water 5 Replace the lid. Incubate the plate at 35 ℃ for one hour. Home Back Next

14. Investigation of protease activities in different fruit juices 6Measure the diameter of the clear zones around the wells by placing the plate on a graph paper and examining against light. Home Back Next