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Effect of temperature on enzyme kinetics




        To determine effect of temperature on the reaction rate of amylase enzyme.




Enzymes are large globular proteins which act as biological catalysts. They increase the rate of reaction without being used up by themselves. They are found in and out of cells and lower the activation energy of a reaction. Amylase is the enzyme which catalyses starch hydrolysis. Alpha amylase and beta amylase are two types of amylase enzymes. The amylase which is the most commonly found in the human body is the alpha amylase. Beta amylase is mainly found in bacteria, fungi and plants. Amylase breakdown starch into maltose. During the process of hydrolysis, Amylase degrades starch by splitting the long glucose units into smaller intermediates and finally producing a complex mixture containing predominantly maltose, which is two glucose molecules bonded together. 

The effect of temperature upon enzyme systems is an interesting area since enzymes been discovered over a century ago. The effects on the activity of amylase breaking down starch are monitored by changing of the temperature of amylase and starch. The temperature ranges over which enzymes show activity is limited between the melting point (0 degree celcius) and boiling point (100 degree celcius) of water. If the temperature is too low, there can be no noticeable reaction rate since the enzyme is operating at a temperature too below its optimum. If the temperature at which the enzyme is operating at is well above 100oC, then thermal deactivation can occur. This occurs because as the high temperature produce enough thermal energy to break some of the intramolecular interactions between polar groups ( Hydrogen bonding, dipole-dipole attractions, ionic interactions) as well as the hydrophobic  forces between the non polar groups within the enzyme structure.  When these forces are disturbed, the secondary and tertiary levels of the enzyme structure changed to a random coiled form that alter the active site’s confirmation beyond its ability to bind the substrate molecule as it was proposed to catalyze. The overall phenomenon is called “Thermal deactivation or Denaturation”.






Rate of reactions including those catalyzed by enzymes are rise with increase in temperature based on the Arrhenius equation K= Ae-ΔEa/RT where K is the kinetic rate constant for the reaction, A is the Arrhenius constant also known as the frequency factor. ΔG is the standard free energy of activation (KJ) which depends on entropic and enthalpic factors, R is the universal gas constant and T is the absolute temperature. Increase in the temperature of a system results from the increase in the kinetic energy of the system. When a molecule collides, the kinetic energy of the molecules is converted in to chemical potential energy of the molecules. Thus greater K.E of the molecules in a system automatically increases the resulting chemical potential energy. As the temperature increases it is possible that more molecules per unit time will reach the activation energy. Thus rate of the reaction is may increases.  Inorder to convert substrate into product, enzymes must collide with and bind to the substrate at its active site. Increase in temperature of a system will increase the number of collisions of the enzyme and substrate per unit time. Thus within limits, the rate of the reaction will increases.



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