Prokaryotes and Eukaryotes

Prokaryotes and eukaryotes are two fundamental categories of cells, distinguished primarily by their cellular structure.

Prokaryotes

1. Definition: Prokaryotic cells are simple, single-celled organisms without a nucleus or other membrane-bound organelles.
2. Examples: Bacteria and Archaea.
3. Characteristics:
   • Nucleus: They lack a true nucleus; instead, their genetic material is located in a region called the nucleoid.
   • Cell Size: Generally smaller than eukaryotic cells, usually around 0.1–5.0 µm in diameter.
   • Cell Structure: They have a simpler structure, with a cell membrane, cytoplasm, ribosomes, and often a cell wall. Some also have flagella for movement.
   • Reproduction: They reproduce asexually through binary fission.
   • Genetic Material: Circular DNA, often with additional small DNA molecules called plasmids.

Eukaryotes

1. Definition: Eukaryotic cells are more complex and can be either single-celled or multicellular organisms. They have a true nucleus and membrane-bound organelles.
2. Examples: Plants, animals, fungi, and protists.
3. Characteristics:
   • Nucleus: A well-defined nucleus containing the cell’s genetic material (DNA) enclosed by a nuclear membrane.
   • Cell Size: Generally larger than prokaryotic cells, typically 10–100 µm in diameter.
   • Cell Structure: Complex structure with various organelles like mitochondria, endoplasmic reticulum, Golgi apparatus, lysosomes, and in plant cells, chloroplasts. They also have a cytoskeleton that provides structural support.
   • Reproduction: Can reproduce both sexually (through meiosis and fertilization) and asexually (through mitosis).
   • Genetic Material: Linear DNA organized into chromosomes within the nucleus.

Key Differences

• Nucleus: Prokaryotes lack a nucleus, while eukaryotes have a true nucleus.
• Size and Complexity: Prokaryotic cells are smaller and simpler, whereas eukaryotic cells are larger and more complex.
• Organelles: Eukaryotic cells contain membrane-bound organelles; prokaryotes do not.
• Reproduction: Prokaryotes reproduce by binary fission, while eukaryotes can reproduce sexually or asexually.

These distinctions are fundamental to the classification of all living organisms.