Cells and compartmentalization
Prokaryotic cells lack a membrane-bound nucleus; their DNA occupies a nucleoid region. Eukaryotic cells enclose most of their DNA in a nucleus and use organelles to separate incompatible reactions and concentrate reactants. Internal membranes create additional working surfaces. Ribosomes are not membrane-bound organelles and occur in both groups. Compartmentalization lets a cell maintain local conditions, such as an acidic lysosome, without exposing the entire cytosol to that environment. Cell walls provide support outside the plasma membrane in plants, fungi, and many prokaryotes, but their chemistry differs among groups.
A lysosome can contain digestive enzymes in an acidic compartment while the surrounding cytosol remains near a different pH. The membrane helps preserve distinct conditions; it does not make molecules teleport.
Prokaryotes are not empty bags without organization. They have membranes, ribosomes, DNA, and regulated biochemical processes, even though they lack the classic eukaryotic membrane-bound organelles.