Activation energy ( EA )

Activation energy ( E_A )

·         To understand how an enzyme speeds up a chemical reaction, it is necessary to define the activation energy of a reaction. There is usually an energy barrier to every chemical reaction which prevents the reaction from spontaneously occurring, even if the reaction is exergonic. This energy barrier is called the activation energy (E_A).

·         Activation energy ( E_A ) is the minimum energy which is needed to break the bonds in a molecule and start a reaction so that an effective reaction can occur.

·         Enzymes speed up metabolic reactions by lowering energy barriers and increasing the number of molecule with a sufficient energy content to react and form a product.

·         Enzymes lower (E_A) so that the transition state can be reached at cellular temperatures. Reactant must absorb enough energy (E_A) to reach the transition state ( uphill portion of the curve )

·         The enzymes act by forming an unstable enzyme-substrate complex with the substrates. This complex is subsequently transformed into the product with the release of the enzyme ( downhill portion of the curve )

Keyword:

Transition state : The unstable condition of reactant molecules that have absorbed sufficient free energy to react.