In biology, cells that perform a specific function within the organism are summarized as a cell type or type of cell .
Due to their function, they often have a shape corresponding to this function. There are different cell types, especially in multicellular organisms . Cells of the same cell type or from different, closely functionally related cell types, form a tissue , and different tissues that support each other in their function form an organ . When a cell changes from one cell type to another, this process is known as differentiation . The appearance often changes. The genetic information, the genome , remains unchanged in most cases, but the proteome and the epigenetic code change. During the development of multicellular organisms, some differentiation steps are irreversible, so that a fully differentiated cell is not able to change into any other cell. Only stem cells or meristem cells can do this . Immortalized cell types are called cell lines in cell culture .
Differentiation of cell types
The fundamental distinction is that between the eucyte (cell of the eukaryotes and thus of all higher organisms) and the protocyte (cell of the prokaryotes ). The names for the individual cell types have become established over time. In plants, tissues are primarily differentiated and most cell types are named after them, e.g. B. parenchymal cell or epidermal cell . The different cell types arise due to different cell origins and have characteristic cell type markers .
The simplest feature to distinguish the different cell types is their shape and size. A human egg cell , for example, has a diameter of about 0.1 mm, so it is just visible to the naked eye. It can microscopically z. B. two different forms of fat cells can be distinguished. The shape of the fat cells in white adipose tissue differs significantly from the shape of the fat cells in brown adipose tissue . The shape also offers a clear possibility of differentiation.
Since differentiated cells fulfill different tasks, the cell organelles are different in the different cell types. These can be stained differently using histological staining . A comparison of red blood cells and nerve cells , for example, shows in the microscopic magnification that nerve cells have a “grainy” appearance with a special color, but the red blood cells look different.
Certain cell types e.g. B. the immune system cannot be distinguished by the shape or the chemical color. A special type of staining ( immunostaining ) can be used here by differentiating and classifying the different surface proteins. One division for this is the cluster of differentiation . The T lymphocyte is an example . One possibility to differentiate immune cells according to their size and granularity as well as their surface molecules is a measurement in a flow cytometer . The B lymphocytes can be distinguished from the plasma cells by their differentiated form using the CD 20 . The CD 20 is expressed on the surface of the B lymphocytes. It is positive for all B lymphocytes, the detection of CD 20 is always negative for plasma cells.
Examples of animal cell types
- B lymphocyte
- Egg cell
- Nerve cell
- Sperm (sperm cell)
- Stem cell
- T lymphocyte
Examples of plant cell types
- Meristem cell
- Apex cell
- Parenchymal cell
- Sieve cell
- Sclerchymal fiber
- Stone cell
- Epidermal cell
- Guard cell
- Jonathan Bard et al .: An ontology for cell types , Genome Biology 2005, 6: R21 doi : 10.1186 / gb-2005-6-2-r21
- Stephen M. Schwartz : The Definition of Cell Type
- M. Gremse, A. Chang et al. a .: The BRENDA Tissue Ontology (BTO): the first all-integrating ontology of all organisms for enzyme sources ; In: Nucleic acids research , Volume 39, Database issue January 2011, pp. D507 – D513, ISSN 1362-4962 , doi : 10.1093 / nar / gkq968 , PMID 21030441 , PMC 3013802 (free full text).