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All living organisms are categorized into two fundamental types of cells: prokaryotic and eukaryotic.
This distinction is based on cellular structure and complexity. Prokaryotes include bacteria and archaea, while eukaryotes encompass a broad range of organisms including animals, plants, fungi, and protists.
Prokaryotes
Prokaryotes are unicellular organisms that lack a defined nucleus and membrane-bound organelles. They are simpler and smaller than eukaryotic cells.
Characteristics of Prokaryotes
Cell Structure
Nucleus: No true nucleus; instead, they have a nucleoid region where the DNA is located.
DNA: Single, circular chromosome. Plasmids (small circular DNA molecules) may also be present.
Cell Membrane: Surrounded by a plasma membrane and often a rigid cell wall.
Ribosomes: Smaller (70S) than those in eukaryotic cells.
Organelles: Lack membrane-bound organelles. Functions are carried out in the cytoplasm or at the cell membrane.
Size: Smaller, typically 0.1-5.0 µm in diameter.
Reproduction
Binary Fission: Asexual reproduction where the cell divides into two genetically identical cells.
Examples
Bacteria (e.g., Escherichia coli, Streptococcus)
Archaea (e.g., Methanogens, Halophiles)
Eukaryotes
Eukaryotes are organisms whose cells contain a true nucleus and membrane-bound organelles.
They can be unicellular or multicellular, and they exhibit a higher level of complexity than prokaryotic cells.
Characteristics of Eukaryotes
1) Cell Structure
Nucleus: Defined, membrane-bound nucleus containing the cell's genetic material.
DNA: Linear chromosomes within the nucleus.
Cell Membrane: Plasma membrane encloses the cell. In plants, fungi, and some protists, there is also a rigid cell wall.
Ribosomes: Larger (80S) than those in prokaryotic cells.
Organelles: Presence of membrane-bound organelles such as mitochondria, endoplasmic reticulum, Golgi apparatus, lysosomes, and (in plants and some protists) chloroplasts.
Size: Larger, typically 10-100 µm in diameter.
2) Reproduction
Mitosis and Meiosis: Mitosis for asexual reproduction and growth; meiosis for sexual reproduction leading to genetic diversity.
3) Examples
Animals (e.g., Humans, Insects)
Plants (e.g., Trees, Flowers)
Fungi (e.g., Yeasts, Mushrooms)
Protists (e.g., Amoeba, Algae)
Key Differences Between Prokaryotes and Eukaryotes
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