Paramecium is free living ciliated Protozoa, its cell body is surrounded by cilia; . The function of the cilia is to allow paramecium to move around in its freshwater habitat, they are also used to waft small bacteria and algaes into the gullet (a large invagination in the cell membrane) where they are endocytosed and assymilated into the cell. All waste excess is exctreted via the anal pore.
Paramecium lives in a freshwater environment which in the abscence of contractile vacuoles would burst this is caused by the osmotic uptake of water, by a process known as osmoregulation . Near to the cell surface membrane, contractile vacuoles have canals and these take up water from the cytoplasm and carry it to the vacuole. The pore opens and the vacuole contracts expelling the water. Within close proximity of the contractile vacuoles are many mitochondria and this is due to the face that the organelles require ATP as its source of energy.
The Paramecium cell reproduces by a process called conjugation. andasexual fission asexual fission creates two genetically identical daughter cells. Paramecium has action potentials not unlike those that occur in neurons calcium ions enter the cell through voltage gated channels and cause the rapid depolarisation of the cell and generate an action potential. The repolarising phase is due to the closing of the calcium ion channels and the opening of the potassium ion channels.
Paramecium cells are capable of regulated exocytosis when triggered by an external stimulus. This exocytosis is similar to the release of neurotransmitters by the presynaptic membrane at a synapse. However instead of using it for signalling and depolarising the postsynaptic membrane, it is used as a defence mechanism against predators. 
- ↑ Beale, Goffey and Preer, John R. Jr. (2008) Paramecium Genetics and Epigenetics CRC Press, Taylor and Francis Group.
- ↑ L.Prescott, J.Hardley and D.Klein Microbiology 6th Edition New York:McGraw-Hill
- ↑ Eckert, R. and Brehm, P. (1979) Ionic Mechanisms of Excitation in Paramecium. Annual Review of Biophysics and Bioengineering. 8, 353-383
- ↑ Brock Biology of Micro-organisms 12th Edition, Madigan Dunlap Clark, Pg 69
- ↑ Holtzman E, Novikoff A (1984) Cells &amp;amp;amp; Organelles, 3rd edition, USA, CBS College Publishing
- ↑ Genoscope (2007) Paramecium tetraurelia: Paramecium, a model ciliate