Factors That Affect Enzyme Activity

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FACTORS THAT AFFECT ENZYME ACTIVITY

Enzymes are biological catalysts, which speed up the rate of reactions. These catalysts are essential to life as most biological reactions would take place too slowly for life to exist. For example the oxidation of glucose to CO2 and H2O is relatively quick and proceeds almost completely in the direction stated. However, without enzymes, glucose oxidation occurs too slowly at physiological temperatures that the rate is essentially immeasurable. The increase in rate of reaction achieved by the enzymes, depending on the enzyme and reaction, range from a minimum of about a million to as much as a trillion times faster than the un-catalyzed reaction at equivalent concentrations and temperatures. Another significant advantage of enzymes is the fact that they are specific, they only catalyse specific substrates, depending on their shape and the enzymes active site shape. There are substrate concentration, pH, enzyme concentration, temperature, and the presence of inhibitors.

Substrate Concentration

At very low substrate concentration, collisions between enzyme and substrate molecules are infrequent, due to the decrease in the number of substrate molecules for the enzymes to catalyse, and therefore the reaction proceeds slowly. As the substrate concentration increases, the reaction rate initially increases proportionally as collisions between enzyme molecules and substrate molecules become more frequent, due to the increased number of substrate molecules that the enzymes can break down. However, as the substrate concentration continues to rise, the increase in reaction rate gradually decreases, until there comes a point where increasing the substrate concentration has no effect, and the reaction rate does not increase. This is shown on the graph below of rate of reaction to substrate concentration, and the clear decline in increase of reaction rate at higher substrate concentration can be seen.

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The reason for the decline and eventual stoppage in reaction rate in increasing substrate concentration, is due to the fact that the enzymes have now become the main limiting factor, their numbers are constant, and they have a maximum rate at which they break down substrates, so it is inevitable, that as the enzymes reach their maximum capacity (where the number of substrate molecules is more than the enzyme can break down), the increase in rate of reaction will decrease and will eventually reach a maximum.

Temperature

As the temperature increases, the enzyme molecules and the substrate ...

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