The absence of membrane-bound cell organelles is the defining characteristic of prokaryotic cells. Among the five kingdoms, only Monera consists of prokaryotes (bacteria and cyanobacteria). Protista, Fungi, and Animalia are all eukaryotic kingdoms with membrane-bound organelles like nucleus, mitochondria, Golgi apparatus, etc. Therefore, Monera is the correct answer to this question about which kingdom lacks membrane-bound organelles.