An enzyme is a highly specialized protein molecule that acts as a biological catalyst, accelerating various biochemical reactions within living organisms.

Substrates are the specific molecules on which enzymes act. Enzymes recognize and bind to their substrates, facilitating and speeding up the conversion of substrates into products.

The active site refers to the region on an enzyme where substrates bind and undergo chemical reactions. It possesses a unique three-dimensional shape that is complementary to the structure of the substrate.

Activation energy is the minimum amount of energy required for a chemical reaction to occur. Enzymes reduce the activation energy necessary for a reaction, enabling it to proceed at a faster rate.

Catalysis refers to the process by which enzymes facilitate and accelerate chemical reactions without being consumed or permanently altered. Enzymes increase the reaction rate by providing an optimal environment for the reaction to occur.

Enzymes exhibit substrate specificity, meaning they can only catalyze particular reactions involving specific substrates due to the precise fit between the active site and the substrate molecules.