Bt toxin is:
(1) Intracellular lipids
(2) Intracellular crystalline protein
(3) Extracellular crystalline protein
(4) Intracellular polysaccharide
(2) Crystals of Bt toxin are protein crystals formed during sporulation in some Bt strains. Bt produces proteins that aggregate to form a crystal. These crystal proteins are toxic to very specific species of insects yet harmless to humans and the natural enemies of many crop pests.