sentence2_structure: Prokaryotes<>are<>unicellular organisms that lack organelles$$$unicellular organisms<>lack<>organelles surrounded by membranes$$$organelles<>surrounded<>
sentence1: In contrast, a prokaryotic cell (right) does not have membrane-bound DNA and also lacks other membrane-bound organelles as well.
sentence2: Prokaryotes are unicellular organisms that lack organelles surrounded by membranes.
question: Prokaryotes are unicellular organisms that lack organelles surrounded by what?