When a snake flicks its tongue, it is gathering odor particles for transfer to two fluid-filled sacs at the roof of the mouth -- Jacobson's organs -- that lead to a second, smaller olfactory chamber. The tongue is used only to assist in this process; snakes do not have a sense of taste.
A eukaryote is a type of cell (or unicellular organism) that possesses a nucleus and membrane-bound organelles, in contrast to prokaryotes (bacteria and archaea) which don't. Eukaryote means good/true nut/kernel in Greek, referring to the nucleus, while prokaryote means before nut/kernel.
Eukaryotic cells contain a nucleus and membrane-bound organelles. All multicellular organisms consist of eukaryotic cells. Eukaryotic cells are thought to have evolved from primitive single-celled prokaryotic cells. All cells are surrounded by a cell membrane (plasma membrane). The cell membrane is semipermeable, allowing some substances to pass into the cell and blocking others. It is composed of a double layer of phospholipids and embedded proteins. Plant cells have an additional layer surrounding them called the cell wall. The cell wall is made of nonliving material called cellulose. The centrosome (also called the microtubule organizing center) is a small body located near the nucleus. The centrosome is where microtubules are made.