Role of Nitrogen

Bacteriochlorophyll, like chlorophyll, has a porphyrin ring made of four pyrrole rings, each containing nitrogen.
Invertase and pepsin are enzymes, i.e. proteins, built of amino acids, which contain nitrogen.
An idioblast is not a molecule but a type of cell: an isolated cell that differs from the surrounding cells in shape, size or content (e.g. cells containing crystals of calcium oxalate, tannins or oil).
So idioblast is the item in which nitrogen is not listed as a constituent (it is a cell, not a nitrogen-containing compound).