PROKARYOTES (Syllabus: GS Paper 3 – Sci and Tech)
Context: Scientists have discovered that prokaryotes are exceptionally resilient to climate change and may increasingly dominate marine environments as a result. This finding highlights their adaptability and potential impact on ocean ecosystems.
Prokaryotes
- Definition: These are organisms that lack a true nucleus and membrane-bound organelles.
- Genetic Material: Typically a circular DNA molecule, is present in the cytoplasm without being enclosed within a nuclear membrane.
- Types: Bacteria and archaea.
- Features of Prokaryotic Cells:
o Shape: They come in various shapes and sizes (0.5-5 µm), with four basic shapes being rod-like (bacillus), spherical (coccus), comma-shaped (vibrio), and spiral (spirillum).
o Cell Organisation: Prokaryotic cells have a basic structural organisation, which includes a cell wall (except in mycoplasma), cytoplasm, and a plasma membrane. However, they lack a well-defined nucleus.
o Organelles: They lack membrane-bound organelles, except for ribosomes. They do have unique structures called mesosomes, which are extensions of the plasma membrane used for various functions.
o Reproduction: Prokaryotic cells reproduce primarily through binary fission, a type of asexual reproduction.
o DNA: Most prokaryotic cells have a single chromosome, which carries hereditary genes in the form of DNA.
- Eukaryote: Any cell or organism that possesses a clearly defined nucleus.
