The cell wall of eukaryotes can be composed of several different types of complex carbohydrates. Above, the red alga Gelidium has a wall composed of the polysaccharide agar. This substance, also found in the red alga Chondrus (Irish Moss), is the principle substance used as a solidifying agent in microbiological media.
Plant cell walls are composed of cellulose, while those of fungi are composed of chitin and/or glucomannin, all of which are polymers of the simple sugar glucose.
The plasma membrane or plasmalemma of eukaryotic cells is composed primarily of phospholipids punctuated by proteins, very much like the prokaryotic cell membrane. Channel proteins are more common in the membrane of eukaryotes than prokaryotes and sterols used to maintain membrane fluidity are found in all. Cholesterol is found in mammal cells and ergosterol in fungal cells. This difference allows selectively toxic antifungal compounds such as amphotericin B to bind to fungal cell membranes while not affecting human cells.
Eukarytotic cells such as protozoa and animal cells lack cell walls. Some unicellular forms such as Amoeba proteus (above), as well as several forms of leukocytes and macrophages in the human body can ingest large particles through the process of endocytosis, forming pseudopodia to encircle and form vacuoles around the substance. Large particles are engulfed by a process called phagocytosis, while small amounts of extracellular fluid are ingested by a process called pinocytosis. After food particles are digested, wastes are excreted by exocytosis. All of these processes are facilitated by the action of the eukaryote cytoskeleton and are forms of active transport.