Cells are the structural and functional units of all living organisms. Some organisms are unicellular and some are multicellular.Unicellular like bacteria and Multicellular such as humans. Each cell perform its particuler functions.
Cell biology or cytology is the science of studying how cells function such as their reproduction and metabolism, their internal and external anatomy.
Cell Organization
There are two general categories of cells: Prokaryotes and Eukaryotes.
Prokaryotes:
These are the simple and first evolved type of cells on the earth. Basically these organisms lack a nuclear membrane eg. Bacteria. The recent discovery of a second group of prokaryotes, called archaea, has provided evidence of a third cellular domain of life and new insights into the origin of life itself. Prokaryotes also lack intracellular organelles and structures. plasma membrane perform all organelles functions.
Prokaryotes are capable of inhabiting almost every place on the earth. Prokaryotes do not develop multicellular forms but some of the bacteria grow in cells and each cell in the colony is identical and capable of independent existence. After cell division,cells do not separate from each other, these always place adjacent to each other because of a common sheath or slime secreted by the cells which enclosed these cells.
Prokaryotic cells have three architectural regions:
1. Appendages called flagella and pili—proteins attached to the cell surface.
2. A cell envelope consisting of a capsule, a cell wall, and a plasma membrane.
3. Cytoplasmic region that contains the DNA and ribosomes and various sorts of inclusions.
Prokaryotic organelles and cell components are carboxysome, chlorosome, flagellum, magnetosome, nucleoid, plasmid, ribosome, thylakoid.
Eukaryotes:
Eukaryotic cells are organized into complex structures enclosed within membranes, that membrane bound complex structure is known as ‘NUCLUES’(eukaryotic cell’s DNA). In membrane bound structures specific metabolic activities take place. Eukaryotes also reffered as true nucleus organisms.
These include fungi, animals, and plants as well as some unicellular organisms.
Organelles are the small organs or specialized subunits of Eukaryotes with in a cell which perform particuller functions. Usually separately enclosed within its own lipid membrane.
chloroplast,endoplasmic reticulum,Golgi apparatus,mitochondrion,vacuole are some of the examples of major Eukaryotic cells organelles.
Without eukaryotes, the world would lack mammals, birds, fish, invertebrates, mushrooms, plants, and complex single-celled organisms.
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