12.0 Enzyme as catalysts

12.1 Characteristics of Enzymes
12.2 Mechanism of enzyme catalysis
12.3 Autocatalysis
12.4 Induced catalysis

All biological reactions are catalysed by special catalysts called enzymes. Thus, enzymes are defined as bio-chemical catalysts. Chemically, all enzymes are globular proteins (which are complex nitrogeneous compounds) with high molar mass ranging from $15000$ to $1000000$ $g\;mo{l^{ - 1}}$ and form colloidal solution in water.

Every biological reaction requires a different kind of enzyme. Since there is a large number of such biological reactions, therefore, there is a large number of enzymes functioning in a living system. Enzymes are vital for biological processes. Without them, the life processes would be very slow and sluggish.