What is a Eukaryotic Cell ?

Eukaryotic cells are the type of living cells that form the organisms of all of the life kingdoms except monera. Protista, fungi, plants and animals are all composed of eukaryotic cells.

What about living cells that are not eukaryotic ?
Not all cells are eukaryotic. There are also prokaryotic cells
(see prokaryotic cell structure), such as the cells of blue-green algae and many different types of bacteria.

Examples of Eukaryotic Cells

Examples of eukaryotic cells include plant cells and animal cells, but not bacteria (which are prokaryotic cells).

Examples of specific types of plant, animal and other eukaryotic cells could also be given as examples of eukaryotic cells, e.g.

• muscle fibres, leucocytes and neuroglia which are types of animal cells, and
• parenchyma cells, collenchyma cells and sclerenchyma cells, which are types of plant cells.

There are numerous specific examples of eukaryotic cells including over 200 different types of cells are identifiable in human tissue alone.

Features of a general Eukaryotic Cell

Eukaryotic cells are often described by comparision with prokaryotic cells. There are many differences between these types of cells, the simplest distinction being that as prokaryotic cells are more primative than eukaryotic cells, eukaryotic cells are generally larger and much more sophisticated than prokaryotic cells due to the presence of a complex series of membranes that divide a typical eukaryotic cell into compartments and also due to the many different types of specialized organelles present in most eukaryotic cells. These features result in most eukaryotic cells being complex structures that have many self-controlled systems, e.g. for generating energy, moving materials around, and even self-destruction in appropriate circumstances.
See compare prokaryotic vs eukaryotic cells for more about the differences between eukaryotic and prokaryotic cells.

The following short list of key features of eukaryotic cells can be used to describe eukaryotic cells without much reference to prokaryotic cells.

• Contain membranous and non-membranous organelles that have specific functions within the cell.
  For example, all eukaryotic cells have (or had*¹) a nucleus. Different eukaryotic cells contain different types and quantities of other organelles depending on the type and function of the particular cell e.g. many plant cells contain chloroplasts which are the sites of photosynthesis within those cells.
  *¹Mature red blood cells (erythrocytes) in mammals are anucleate, i.e. they have no nuclei, when they are mature. This, together with the lack of many other organelles, results in increased accomodation within red blood cells for the haemoglobin that carry oxygen to cells around the body via red blood cells inside blood vessels. However, unlike prokaryotic cells, those cells did have nuclei at earlier stages in their development.
• Contain linear DNA molecules*² that are larger than the (circular) DNA molecules in prokaryotic cells and, in association with proteins, form structures called chromosomes.
  *²As opposed to the circle of double-stranded DNA and sometimes short pieces of circular DNA called plasmids that are present in prokaryotic cells. (The DNA molecules in prokaryotic cellsare not associated with proteins , hence prokaryotic cells don't have chromosomes.)
• Cell division is usually by mitosis, although meiosis applies to some specific types of cells concerned with sexual reproduction.
• Endocytosis is possible for eukaryotic cells.
  This is a process by which small regions (sometimes called 'patches') of cell membrane leave the membrane that encloses the cell, forming instead much smaller membrane-bound vesicles that are able to deliver substances such as nutrients from the external environment to locations deep within the cell. This mechanism enables eukaryotic cells to have larger sizes than would otherwise be possible - i.e. if transport of nutrients into the cell were only possible via simple diffusion.
  (For more about the movement of substances into and out of cells see movement across membranes.)

Reminder in pictures:

See also a comparison between animal cells, plant cells and bacteria cells.