Prokaryotic cells occurs in pplo,cyanobacteria,bacteria
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The following points highlight the eighteen important characteristics of prokaryotic cells.
Characteristic # 1. Nuclear Material:
DNA is naked and lies variously coiled in the cytoplasm. It is often called gonophore, nuclear body or nucleoid. It is equivalent to a single naked chromosome and is, therefore, also called prochromosome. Many prokaryotes also have additional small circular DNA entities called plasmids. Plasmids carry additional specific factors like nitrogen fixation, resistance, fertility, etc.
Characteristic # 2. Nuclear Components:
Nuclear envelope, nucleoplasm, nucleolus and histone covering of chromatin are absent. In eukaryote (= eukaryotic) cells, a typical nucleus is found.
Characteristic # 3. Types:
Prokaryote contains organisms like blue-green algae (BGA = cyanobacteria, e.g., Nostoc), bacteria, pleuropneumonia-like organisms or PPLO (e.g., Mycoplasma), archaebacteria, spirochaetes, rickettsiae and chlamydiae. PPLOs are the smallest free living organisms.
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Characteristic # 4. Cell wall:
It is present in bacteria and cyanobacteria. A cell wall is absent in mycoplasma or PPLO.
Characteristic # 5. Flagella and Fimbriae:
Flagella are present in some bacteria only (Fig. 8.6). The bacterial flagella are single-stranded as compared to 11-stranded flagella of eukaryotes. In some bacteria, non-motile appendages called pili or fimbriae also occur. They take part in attachment (e.g., Neisseria gonorrhoeae) and conjugation (e.g. Escherichia coli).
Characteristic # 1. Nuclear Material:
DNA is naked and lies variously coiled in the cytoplasm. It is often called gonophore, nuclear body or nucleoid. It is equivalent to a single naked chromosome and is, therefore, also called prochromosome. Many prokaryotes also have additional small circular DNA entities called plasmids. Plasmids carry additional specific factors like nitrogen fixation, resistance, fertility, etc.
Characteristic # 2. Nuclear Components:
Nuclear envelope, nucleoplasm, nucleolus and histone covering of chromatin are absent. In eukaryote (= eukaryotic) cells, a typical nucleus is found.
Characteristic # 3. Types:
Prokaryote contains organisms like blue-green algae (BGA = cyanobacteria, e.g., Nostoc), bacteria, pleuropneumonia-like organisms or PPLO (e.g., Mycoplasma), archaebacteria, spirochaetes, rickettsiae and chlamydiae. PPLOs are the smallest free living organisms.
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Characteristic # 4. Cell wall:
It is present in bacteria and cyanobacteria. A cell wall is absent in mycoplasma or PPLO.
Characteristic # 5. Flagella and Fimbriae:
Flagella are present in some bacteria only (Fig. 8.6). The bacterial flagella are single-stranded as compared to 11-stranded flagella of eukaryotes. In some bacteria, non-motile appendages called pili or fimbriae also occur. They take part in attachment (e.g., Neisseria gonorrhoeae) and conjugation (e.g. Escherichia coli).
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