Safety precautions:- For safety during the experiment safety glasses will be worn for the protection of the eyes. Long hair will be tied back as to keep it from getting in the solutions or covering the eyes. Lab coats will be worn in order to protect clothes from spillages.
Apparatus:- Five water baths, at different temperatures
Fifteen boiling tubes/test tubes
Test tube rack
Five tit pipettes
Pitted tile
Five thermometers
Stop watch
Syringe
Five glass rods
Prediction:- From this experiment I expect to that the fastest reaction will take place at, approximately, body temperature, 37oC. As the temperature decreases I expect the rate of the enzyme reaction to decrease. As the temperature increases, above 37oC, I expect the rate of enzyme reaction to decrease.
Explanation of prediction:- I believe that I will find the above results due to my scientific knowledge. Protein has a particular shape, enzymes, therefore, have a particular shape, seeing as they are proteins. Enzymes can only work by colliding with complementary substrates. The active site of an enzyme molecule has a distinctive composition in to which specific substrate molecules will fit. The shape and position of chemical groups in it certify only the substrate molecules with the complementary shape and structure will combine with the enzyme.
As the temperature of the amylase and starch solution increases the movement of enzymes increases, therefore, increasing the frequency of collisions, hence the enzyme reaction rate increases. As the temperature decreases the movement of enzymes decreases, hence the frequency of collisions is decreased and the enzyme reaction rate decreases. It is proven that amylase works most efficiently at approximately 37oC, this is because the enzyme is specifically used in the body, which holds this approximate temperature constantly. Although when the temperature increases the rate of the enzyme increases at a certain point this will not happen, this is known as the denaturation point. At the denaturation point the enzyme’s actives sites alter in shape. This happens because with the increase in temperature the particles of the enzyme vibrate. The vibrations cause the bonds between the particles to break and they become long and fibrous. For this reason, the once complementary shape of the substrate (starch) no longer fits properly. The substrate and the active sites of the enzyme do not lock as they should, therefore the reaction rate will decrease.
Fair test:- The factor which will be varied is temperature. This factor will be varied because this is what my interests are in for this experiment. I am trying to find out how temperature affects the rate of an enzyme catalysed reaction. In order for this to be a fair test, some factors must remain the constant, these are, concentration and volume of the enzyme and the substrate, the surrounding environment and the time scales. These factors will be kept constant in order to insure the experiment is carried out in a way which the affect of temperature, rather than anything else (like concentration), can be monitored on the rate of an enzyme catalysed reaction. For this to be a completely fair test there should be a 'control', unfortunately this is impossible as the appropriate control would be a solution kept in an atmosphere with no temperature, as this is impossible the best control is a solution which contains no enzyme, this would be to prove that temperature alone does not break down starch. Due to lack of time the results for this control will be taken from a previous experiment, the model gut experiment.
Prelimary work:- Work which has been done at previous times on enzymes include the model gut experiment and the action of lipase. These experiments aided me to make predictions because of previous results. The experiment done on the action of lipase showed that without an enzyme (lipase) the substrate (fat) was not broken down. The concentrations and volumes used were decided from the previous model gut experiment.
