Their mechanisms are simpler than later-evolved eukaryotes, which contain a nucleus that envelops the cell's DNA and some organelles.Both have plasma membranes and ribosomes (structures that synthesize proteins[clarification needed] and float free in cytoplasm).Two unique characteristics of prokaryotes are fimbriae (finger-like projections on the surface of a cell) and flagella (threadlike structures that aid movement).The nucleus, the feature of a eukaryote that distinguishes it from a prokaryote, contains a nuclear envelope, nucleolus and chromatin.In cytoplasm, endoplasmic reticulum (ER) synthesizes[clarification needed] membranes and performs other metabolic activities.The Golgi apparatus consists of multiple membranous sacs, responsible for manufacturing and shipping out materials such as proteins.[3] Endocytosis is a form of active transport where a cell takes in molecules, using the plasma membrane, and packages them into vesicles.