File Name: lock and key model .zip
In biology , the active site is region of an enzyme where substrate molecules bind and undergo a chemical reaction.
In the Lock and Key Model, first presented by Emil Fisher, the lock represents an enzyme and the key represents a substrate. It is assumed that both the enzyme and substrate have fixed conformations that lead to an easy fit. Because the enzyme and the substrate are at a close distance with weak attraction, the substrate must need a matching shape and fit to join together. At the active sites, the enzyme has a specific geometric shape and orientation that a complementary substrate fits into perfectly. The theory behind the Lock and Key model involves the complementarity between the shapes of the enzyme and the substrate. Their complementary shapes make them fit perfectly into each other like a lock and a key. According to this theory, the enzyme and substrate shape do not influence each other because they are already in a predetermined perfectly complementary shape.
The lock and key mechanism is a metaphor to explain the specificity of the enzymes active site and the substrate. In the same way only certain keys fit a lock, only certain substrates fit an enzyme's active site. The substrate is specific to a certain active site. When the correct substrate binds to the enzyme's active site, an Enzyme substrate complex is formed. The enzyme catalyses a reaction, an Enzyme product complex is formed and the product is released.
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Mechanism of Enzyme Action. Introduction - Enzyme Characteristics:. The basic mechanism by which enzymes catalyze chemical reactions begins with the binding of the substrate or substrates to the active site on the enzyme. The active site is the specific region of the enzyme which combines with the substrate. The binding of the substrate to the enzyme causes changes in the distribution of electrons in the chemical bonds of the substrate and ultimately causes the reactions that lead to the formation of products.
Enzymes are proteins that function as biological catalysts. So, they are molecules that speed up a chemical reaction without being changed by the reaction. Enzymes are folded into complex 3D shapes that allow smaller molecules to fit into them. The place where these molecules fit is called the active site. In the lock and key hypothesis , the shape of the active site matches the shape of its substrate molecules.
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