By virtue of the structural differences, there are basically two different types of cells that can be considered, namely prokaryotic and eukaryotic.The pro -karyon (or the cell without the karyon or nucleus in Greek) are the bacteria and the cyanobacteria (according to the five kingdom classification by Whittaker(1969) .On the contrary, the eukaryotes demonstrated many developed characteristics than the prokaryotes.
BASIC CHARACTERS OF PROKARYOTES
- Simple organization, smaller size (0.1– 0.25 mm),found in land ,air and water
- A true nucleus with nuclear membrane absent, and is called nucleoid, nucleolus and centrioles absent,no meiotic reduction
- All well defines cytoplasmic organelles like mitochoindria, Golgi bodies, lysosomes,
- Ribosomes remain scattered in the cytoplasm,but DNA is without histones and is a double stranded DNA
- Ribosomes are 50S and 30 S. Jointly 70S
- Cell wall composed of carbohydrate, muramic acid and amino acid, may extend into cytoplasm as mesosome with respiratory enzymes.
- Absence of cytoplasmic movement, locomotion is by flagella that is not multistranded and made of flagellin
- Absence of splicing mechanism as post transcriptional modification, nickase enzyme is absent
- High genetic flexibility and biochemical adaptability.
- Prokaryotes are usually spherical, or comma shaped, or rod or spiral in shape
Besides, the prokaryotes (Bacteria ) are very important for the maintenance of the ecosystem, they not only act as saprophytes but also help in digestion as well as clean oil spills at sea.