Amylase Starch Maltose I2KI starch
Like most chemical reactions, the rate of an enzyme-catalyzed reaction increases as the temperature is raised. A ten degree Centigrade rise in temperature will increase the activity of most enzymes by 50 to 100%. Variations in reaction temperature as small as 1 or 2 degrees may introduce changes of 10 to 20% in the results. In the case of enzymatic reactions, this is complicated by the fact that many enzymes are adversely affected by high temperatures. As shown in Figure 13, the reaction rate increases with temperature to a maximum level, then abruptly declines with further increase of temperature. Because most animal enzymes rapidly become denatured at temperatures above 40*C, most enzyme determinations are carried out somewhat below that temperature.
Over a period of time, enzymes will be deactivated at even moderate temperatures. Storage of enzymes at 5*C or below is generally the most suitable.
Some enzymes lose their activity when frozen.
Lock and key hypothesis
This is the simplest model to represent how an enzyme works. The substrate simply fits into the active site to form a reaction intermediate.
Induced fit hypothesis
In this model the enzyme molecule changes shape as the substrate molecules gets close. The change in shape is 'induced' by the approaching substrate molecule. This more sophisticated model relies on the fact that molecules are flexible because single covalent bonds are free to rotate.
Temperature is one of the factors affecting catalytic activity of enzymes
As the temperature rises, reacting molecules have more and more kinetic energy. This increases the chances of a successful collision and so the rate increases. There is a certain temperature at which an enzyme's catalytic activity is at its greatest (see graph). This optimal temperature is usually around human body temperature (37.5 oC)...