Why does an Enzyme-Substrate Complex have slightly less energy than the substrate alone?
The formation of an enzyme-substrate complex involves the binding of a substrate molecule to the active site of an enzyme. This binding is driven by multiple interactions including hydrogen bonds, electrostatic interactions, and hydrophobic interactions.
The reason why the enzyme-substrate complex has slightly less energy than the substrate alone can be explained by the concept of the transition state. In any chemical reaction, there is an intermediate stage during which the bonds in the reactants are partially broken and new bonds start to form. This intermediate state is known as the transition state
Enzymes facilitate chemical reactions by lowering the activation energy required for the reactants to reach the transition state. Activation energy is the energy required to break the existing bonds and initiate the reaction. Enzymes accomplish this by stabilizing the transition state, making it easier for the reactants to overcome the energy barrier and proceed with the reaction
When a substrate molecule binds to the active site of an enzyme, the enzyme undergoes a conformational change forming an enzyme-substrate complex. This conformational change facilitates the transition state formation by bringing the substrate into the optimal orientation for the reaction to occur. The active site of the enzyme provides an environment that allows the substrate to overcome the energy barrier more easily
Additionally, enzymes can use different mechanisms to promote the reaction. For example, enzymes can provide a microenvironment with a specific pH or specific chemical groups that can participate in the reaction. These mechanisms further lower the energy required for the reaction to take place
Overall, the formation of an enzyme-substrate complex decreases the energy required for a chemical reaction to occur, resulting in a lower energy state compared to the substrate alone. This is primarily achieved through the stabilization of the transition state by the enzyme, making it more favorable for the reaction to proceed
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