Enzyme-controlled reaction, factors that affect the chemical structure and properties of the enzyme.

Essay by SminksterCollege, Undergraduate April 2003

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Write an explanation of how any two factors affect the rate of an enzyme-controlled reaction. How do these factors affect the chemical structure

and properties of the enzyme.

Many things can affect the rate of enzyme activity. The temperature of the enzyme, the pH of the solution, the concentration of the enzyme, substrate and the product. Also, another affector is the number of competitive and non-competitive inhibitors.

As I cannot explain them all, I have chosen to explain the effect of temperature and also the effect of inhibitors on enzyme activity.

Temperature :

As the temperature is increased the kinetic theory is applied. More energy is present and the molecules move fast. This increases the chance of collision between the enzymes and substrate and so increasing the rate of reaction. At these higher temperatures the active site of the enzyme is actually fairly flexible. The heat has broken a small number of Hydrogen bonds which hold the site to its shape.

According to the lock and key theory the enzyme's active site is specific to the substrate and so they fit together. The enzyme only catalases a single reaction. As the site is now flexible, there is an increased amount of induced fit and so the production of an enzyme-substrate complex is more likely. If the temperature is lower, the active site of the enzyme is much less flexible as there is the maximum number of bonds present holding it all together. At the optimum temperature shown on the curve, the conditions are perfect for this enzyme to work in. Different enzymes have different optimums. For example, human enzymes work at body temperature whereas there are thermophilic/stable enzymes which are optimum at much higher temperatures such as 85C. Once the enzyme-substrate complex has been formed, the activation energy is...