Both ways of inducing active immunity (vaccines and direct environmental exposure to an antigen) will ultimately result in the production of antibodies. which of the five classes of antibodies is the first to be secreted during the primary response after the initial exposure to the antigen?

Lactase is essential for digesting lactose in milk. this enzyme is specific for this sugar. why? molecules and active sites vary in size; only properly sized molecules can fit. there is a precise compatibility between the active site and the lactose molecule. specificity refers to the action of the enzyme, such as hydrolysis, and relatively few molecules can be hydrolyzed. reaction-specific enzymes assume a fit by folding around the most numerous substrate molecules.