Which kingdom consists of unicellular prokaryotes whose cell walls do not contain peptidoglycan?

• A. Protoarchaeota
• B. Archaebacteria
• C. Eubacteria
• D. Monerans

Answer: (B)

Cell wall materials distinguish major prokaryotic groups, and this question hinges on which group lacks peptidoglycan in its walls. Archaebacteria are unicellular prokaryotes whose cell walls do not contain peptidoglycan; they use different polymers such as pseudopeptidoglycan, and their membrane lipids have distinct chemical structures. This sets them apart from true bacteria, whose cell walls do contain peptidoglycan. The older term Monerans grouped prokaryotes broadly without this specific chemical distinction, making it less precise, and Protoarchaeota isn’t the standard kingdom name used in modern taxonomy. So the best match is Archaebacteria.