Not all cells have a nucleus. Biology breaks cell types into –
(a) Prokaryotic cell
(Pro – before + karyon – nucleus) –
Those with no defined nucleus.
- These cells are generally small, primitive and incomplete.
- These cells do not have a well organized nucleus as nuclear membrane, nucleolus are absent.
- The genetic material is a single chromosome lies in the cytoplasm. The undefined nuclear region in the cytoplasm is called nucleoid.
- Cell organelles such as mitochondria, lysosome, endoplasmic reticulum, chloroplast etc. are not present.Examples – Bacteria and Blue-green algae.
- Cell : The Fundamental Unit of Life
- Morphology of Cells – Size, Shape and Structure
- Outer membrane of Cell – Cell membrane / Plasma membrane
- Outer Membrane of The Cell – Cell wall
(b) Eukaryotic cell
(Eu – true + karyon – nucleus)
Those with a defined nucleus.
- These cells are generally large, advanced and complete.
- These cells have a well organized nucleus as DNA is enclosed by a nuclear membrane and nucleolus is also present.
- The genetic material is composed of two or more chromosomes.
- Cell organelles such as mitochondria, lysosome, endoplasmic reticulum, chloroplast etc. are present in the cytoplasm.
Examples – Fungi, protozoa, higher advanced unicellular and multicellular animal and plant cells.
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