An enzyme is a catalyst, which is a chemical agent that changes the rate of a reaction without being consumed by the reaction.The reactant that an enzyme acts on is called its substrate.While the enzyme is bound to the substrate, the catalytic action converts the substrate to the product.Because of its shape, each enzyme catalyzes a specific reaction (molecular recognition).Only a certain region of the enzyme molecule actually binds to the substrate.This area is called the active site and is usually a groove on the surface of the enzyme.The shape of the active site and the shape of the substrate fits accordantly.When the substrate enters the active site, it induces the enzyme -in a process called induced fit- to change its shape to fit tightly around the substrate.The induced fit is very important during the catalytic cycle when the substrate enters the active site to form an enzyme-substrate complex.The enzymes emerge from the reaction, however, in their original form and are ready to function over and over again. When a reaction rearranges the atoms of molecules, the bonds in the reactants must be broken and the new bonds in the products must be formed.This requires energy.The energy required to break the bonds in the reactant molecules is known as the activation energy. The bonds only break when the molecule has absorbed enough energy (usually in the form of heat) to become unstable.Heat speeds up a reaction, but the high temperature kills cells; therefore, organisms must instead use a catalyst.Enzymes (mostly proteins) are biological catalysts.Enzymes speed up reactions by lowering the barrier of activation energy, so that the transition state is within reach at regular temperatures.A transition state occurs when reactants are in an unstable condition and are ready for the reaction to take place.An enzyme cannot changes the free energy of the reaction or the spontantinuity of the reaction.It can…

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