Final answer:
An enzyme only catalyzes a specific chemical reaction under specific conditions due to the unique shape and chemical environment of its active site, which matches only certain substrates. This specificity is essential for efficient and precise control of biological reactions. Models describing this interaction include lock and key and induced fit.
Step-by-step explanation:
An enzyme catalyzes a specific chemical reaction under specific conditions because of the precise interaction between the enzyme's active site and the substrate it is designed to bind with. The specificity of an enzyme is attributed to the unique three-dimensional shape and chemical environment of its active site, which often only allows a particular substrate or a group of structurally related substrates to bind. This fitting is sometimes described by the lock and key model, or more accurately, the induced fit model, where the active site undergoes a slight change in shape to achieve the optimal binding and catalysis of the substrate, similar to how a glove molds to the shape of a hand.
Also, enzymes function as highly specific catalysts because they contain unique sequences of amino acids that determine their shape and chemical properties. The enzyme's action includes the substrate binding to the active site, undergoing a chemical reaction, and then being released as the product, all while the enzyme remains unchanged and ready to catalyze another reaction.
Without enzymes, biological processes would be extremely slow or nonfunctional. The efficiency and specificity of enzymes allow cells to control chemical reactions precisely, ensuring that necessary processes happen correctly and at a speed that supports life.