Difference between an active site and a substrate in an enzymatic reaction

Active site and substrate are terms commonly used in enzymes. The active site is an area in an enzyme wherein the molecules would bond and allow a chemical reaction to happen. The molecules that bond to the active site are called the substrate. The active sites has residues that would allow for a temporary bond between the site and the substrate. These sites are specific only for a certain substrate. So, if the  active sites and the substrate do not match no reaction would occur. The enzyme or the catalyst is of no use at all in this case. Enzymes are used as catalysts as they hasten the reaction.

The basic building blocks of dna and rna are nucleotides

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