The prokaryotic cells are morphologicallly the most primitive cells. A prokaryotic cell is essentially a single envelope system. It is a simple type of cell in which genetic material is not organised in the form of nucleus, it lies freely in the cytoplasm whence it is known as prochromosome. Prokaryotic cells are known for their rapid multiplication. The prokaryotic cells have the following important features:-
1) Nuclear Material:- DNA is naked and lies variously coiled in the cytoplasm. It is often called genophore, nuclear body or nucleoid. Many prokaryotic also have additional small circular DNA called Plasmid.
2) Nuclear component:- Nuclear envelope, nucleoplasm, nucleolus and histone proteins of chromatin are absent.
3) Types:- Prokaryota contains organisms like blue-green algae ( Cyanobacteria, Nostoc ), bacteria, PPLO ( pleuropneumonia like organism ), archaebacteria, spirochaetes, chlamydiae.
4) Cell wall:- It is present in bacteria and cyanobacteria. Cell wall is absent in mycoplasma or PPLO.
5) Flagella and Fimbriae:- The bacterial flagella are single stranded as compared to 11 stranded in eukaryotes. In some bacteria non-motile appendges called pili or fimbriae also occur.
6) Photosynthetic Thylakoids:- Blue-green algae and some bacteria are photo-autotrophic (who can make their own food with photosynthesis). Their photosynthetic thylakoids lie freely in the cytoplasm.
7) Membrane lined cell organelles:- All double membrane layered organelles are absent like mitochondria. cholroplast, golgi bodies, lysosomes etc.
8) Ribosomes:- Ribosomes are 70s as compared to 80s.
9) One -Envelope System:- There is a single that surrounds the cell. Hence, prokaryotes have a single membrane or one-envelope system.
10) Cyclosis:- Cytoplasm does not show cyclosis or streaming movements ( autonomic vital movements that occurs in cytoplasmic matrix).
11) Spindle:- Mitotic spindle is not formed during cell division.
12) Sexual Reproduction:- It is absent. They multiply very rapidly by asexual means like binary fission, sporulation etc.
12) Transcription and Translation:- Both occurs in cytoplasm ( transcription is a synthesis of RNA over DNA strands and translation is the synthesis of proteins on ribosome)
13) Respiratory Enzymes:- They usually lie in contact with cell membrane.
14) Nitrogen Fixation:- It occurs only in some bacteria and cyanobacteria.
1) Nuclear Material:- DNA is naked and lies variously coiled in the cytoplasm. It is often called genophore, nuclear body or nucleoid. Many prokaryotic also have additional small circular DNA called Plasmid.
2) Nuclear component:- Nuclear envelope, nucleoplasm, nucleolus and histone proteins of chromatin are absent.
3) Types:- Prokaryota contains organisms like blue-green algae ( Cyanobacteria, Nostoc ), bacteria, PPLO ( pleuropneumonia like organism ), archaebacteria, spirochaetes, chlamydiae.
4) Cell wall:- It is present in bacteria and cyanobacteria. Cell wall is absent in mycoplasma or PPLO.
5) Flagella and Fimbriae:- The bacterial flagella are single stranded as compared to 11 stranded in eukaryotes. In some bacteria non-motile appendges called pili or fimbriae also occur.
6) Photosynthetic Thylakoids:- Blue-green algae and some bacteria are photo-autotrophic (who can make their own food with photosynthesis). Their photosynthetic thylakoids lie freely in the cytoplasm.
7) Membrane lined cell organelles:- All double membrane layered organelles are absent like mitochondria. cholroplast, golgi bodies, lysosomes etc.
8) Ribosomes:- Ribosomes are 70s as compared to 80s.
9) One -Envelope System:- There is a single that surrounds the cell. Hence, prokaryotes have a single membrane or one-envelope system.
10) Cyclosis:- Cytoplasm does not show cyclosis or streaming movements ( autonomic vital movements that occurs in cytoplasmic matrix).
11) Spindle:- Mitotic spindle is not formed during cell division.
12) Sexual Reproduction:- It is absent. They multiply very rapidly by asexual means like binary fission, sporulation etc.
12) Transcription and Translation:- Both occurs in cytoplasm ( transcription is a synthesis of RNA over DNA strands and translation is the synthesis of proteins on ribosome)
13) Respiratory Enzymes:- They usually lie in contact with cell membrane.
14) Nitrogen Fixation:- It occurs only in some bacteria and cyanobacteria.
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