Enzymes
What are enzymes?
Enzymes are biological catalysts, protein in nature, which can speed up a chemical reaction by lowering the activation energy without altering themselves.
Catalysts: Catalysts are substances that speed up a chemical reaction but remain chemically unchanged.
Properties of enzymes include:
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Made of Protein
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Enzymes are specific
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Enzymes are denatured at high temperatures
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Enzymes are always produced in living cells
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Small amount of energy is needed to catalyze the reaction
Lock and key hypothesis
All enzymes are protein. They have a specific 3-dimensional shape which has a dent on it known as active site. Substrate molecule having complementary shape to the active site can exactly fit into it, like a key in a lock. As a result, enzyme-substrate complex is formed and enzyme then catalyzes the reaction by lowering the activation energy without altering itself.
Enzyme effectivity
Effect of increasing temperature on a enzyme catalyzed reaction:
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As temperature increases the rate of enzyme catalyzed reaction also increases, but up to a certain temperature.
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The temperature at which the enzyme works best is known as its optimum temperature.
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At temperature above the optimum temperature, the active site gets distorted/ deformed and hence the enzyme is denatured. As a result, no new enzyme – substrate complex can be formed, i.e., the rate of reaction falls to zero.
Effect of pH on enzyme activity:
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Each enzyme can work best at a particular pH which is known as its optimum pH.
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At extreme pH, pH below or over the optimum pH, the active site gets denatured. So, no new enzyme-substrate complex is formed.
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As a result, the rate of reaction of enzyme catalyzed reaction falls to zero.