Organisms that must eat or consume other organisms to obtain energy are: O autotrophs
chemotrophs
o heterotrophs
xylotrophs
A AUTOTROPHS. B Chemotrophs C HETEROTROPHS. D XYLOTROPHS

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.