Enzymes are organic or biological catalyst which are protein in nature and are secreted or produce by living organism or cells, which speedup the rate of a chemical reaction but remain unchanged at the end of the reaction.
Characteristics of enzymes
- Enzymes are soluble in water
- All enzymes are proteins
- Enzymes are specific that is each enzymes act on a particular substrate.
- Enzymes are organic catalyst that is they have the ability to speedup a chemical reaction in the body.
- Enzymes are sensitive to temperature the higher the temperature the higher the rate of reaction lower temperature deactivate the enzyme while extremely high temperature above optimum denature or destroy enzymes.
- The best temperature range is between 35-40° and this is called the optimum temperature.
- Enzymes are sensitive to PH (the degree of acidity or alkalinity)
- Certain chemical substances in the body called inhibitors can deactivate enzymes eg cyanids compound of lead and mecury.
- Many enzymes bring about reversible reaction
- Many enzymes need to be activated by other substances before it can catalise a reaction.
EXPERIMENT TO SHOW THE EFFECTS OF ENZYMES
Aims: TO TEST ENZYMES ACTIVITY
Phyalin: saliva contains the enzyme
A starch solution can be made by adding a little powdered starch to water and boiling the mixture. After cooling the mixture; a little of it( about 5cm3) is poured into each of 5 test tube labelled A,B,C,D and E. A drop of starch solution from each test tube is placed on a white tile and tested with iodine solution. In each case a blue-black colour is formed. Next a solution of saliva is made by collecting some saliva from the mouth and diluting it to double its volume with distilled water. A little of the solution of saliva is then poured in 3 of the test tube in turn( test tubes B,C and D).Test tube A is left without saliva.This will as a control experiment. In the case of test tube E 2cm3 of the solution is first boiled and then added to the starch solution.This is done so as to destroy the enzyme.
A few drops of dilute sodium carbonate as added to the mixture in test tube C and E in turn. This provides an alkaline medium. On the other hand, a few drops of dilute hydrochloric acid are added to the content of the test tube D to provide an acid medium. The solution in the test tube D to provide an acid medium. The solution in the test tube must be stired thoroughly. The content of the test tube A-E are as follows.
A= starch solution only
B=Starch solution and saliva
C=starch solution, saliva and dilute sodium carbonate solution.
D= starch solution, saliva, dilute hydrochloric acid.
E= starched solution, tolled saliva and dilute sodium carbonate solution.
The 5 test tube are placed in water bath and maintained at a temperature of about 36°C which is closed to the body temperature of a mammal. At interval of about 30s a drop of liquid from each of the test tube is extracted with clean pipette, placed on a white tile and tested with iodine solution. In the case of test tube B the tube A produce a blue- black color each time indicating the presence of starch.
