Explain the factors that affect enzyme activity - KCSE Biology Essays

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Temperature; enzymes are protein in nature; and hence sensitive to temperature changes; as temperature increases, enzyme activity also increases until optimum/maximum; above this optimum the reaction decreases sharply; due to the destruction of the enzyme structure/become denatured; making the enzyme ineffective/non-functional; most enzymes have optimum temperature of between 35oC and 40oC; when temperature decreases, the rate of enzyme reaction decreases as the enzyme becomes inactivated;

pH/acidity or alkalinity; most enzymes have optimum pH of close to 7/neutral which is the intracellular pH; however some enzymes work best in an alkaline medium while others work best in an acidic medium/condition; as the pH exceeds optimum, the enzyme activity decreases; extreme acidity or alkalinity denatures most enzymes;

Substrate concentration and enzyme concentration; enzyme reaction increases with increase in substrate concentration; up to a certain level where further increase in
substrate concentration does not increase the rate of enzyme reaction; this is because when substrate concentration is increased, all the active sites of the enzyme are occupied; however, when the enzyme molecules are increased, there is a proportional increase in the maximum rate of enzyme action; enzymes are however required in small amounts hence; they speed up the rate of biochemical reactions without altering the equilibrium;

Enzyme cofactors/coenzymes; these are non-proteinous substances which activate the enzymes; most enzymes will not work without them; examples of cofactors are metallic ions such as iron, magnesium, zinc, copper and also vitamins as enzyme coenzymes; these substances are required in small amounts and are used repeatedly/can be recycled;

Enzyme inhibitors; these are substances that inhibit enzyme action by competing with the normal substrate for the active sites; there are two types: competitive and non-competitive; competitive inhibitors have no permanent effect on the enzyme action; while non-competitive inhibitors combine permanently with the enzyme molecules thus distorting or blocking the active sites permanently; examples of these inhibitors include cyanides, mercury, silver; inhibition can be reduced by reducing the concentration of the inhibitors; or by increasing the substrate concentration;

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