Prokaryote and Eukaryote: Study Notes

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Prokaryotes and Eukaryotes

• Nucleus:
  • Prokaryotic Cells: Absent; instead, there is a nucleoid region.
  • Eukaryotic Cells: Present, with a well-defined nuclear membrane.
• DNA Structure:
  • Prokaryotic Cells: Circular, not enclosed in a membrane.
  • Eukaryotic Cells: Linear, enclosed within the nucleus.
• Cell Size:
  • Prokaryotic Cells: Generally small (0.1–5.0 µm).
  • Eukaryotic Cells: Larger (10–100 µm).
• Cell Membrane:
  • Prokaryotic Cells: Present, phospholipid bilayer.
  • Eukaryotic Cells: Present, phospholipid bilayer.
• Organelles:
  • Prokaryotic Cells: Lack membrane-bound organelles.
  • Eukaryotic Cells: Contains membrane-bound organelles (e.g., mitochondria, endoplasmic reticulum, Golgi apparatus).
• Ribosomes:
  • Prokaryotic Cells: Smaller (70S).
  • Eukaryotic Cells: Larger (80S).
• Cell Wall:
  • Prokaryotic Cells: Present in most, such as bacteria (made of peptidoglycan).
  • Eukaryotic Cells: Present in plants (cellulose) and fungi (chitin), but absent in animal cells.
• Reproduction:
  • Prokaryotic Cells: Asexual (binary fission).
  • Eukaryotic Cells: Both sexual (meiosis) and asexual (mitosis).
• Plasmids:
  • Prokaryotic Cells: Often present, carrying additional genetic information.
  • Eukaryotic Cells: Rarely present.
• Cytoskeleton:
  • Prokaryotic Cells: Absent or very rudimentary.
  • Eukaryotic Cells: Well-developed, with microtubules, microfilaments, and intermediate filaments.
• Flagella:
  • Prokaryotic Cells: Simple structure, made of protein flagellin.
  • Eukaryotic Cells: Complex structure, made of tubulin.
• Metabolism:
  • Prokaryotic Cells: Can be anaerobic or aerobic.
  • Eukaryotic Cells: Primarily aerobic, but some eukaryotes can be anaerobic.
• Examples:
  • Prokaryotic Cells: Bacteria, Archaea.
  • Eukaryotic Cells: Plants, Animals, Fungi, Protists.

Cell Membrane (Plasma Membrane)

• Composition: Composed of a phospholipid bilayer with embedded proteins, cholesterol, and carbohydrates.
• Structure: A semi-permeable membrane that controls the movement of substances in and out of the cell.
• Function: Regulates the passage of materials, communicates with other cells, and provides a boundary between the cell's internal environment and the external environment.
• Occurrence: Present in all cell types (prokaryotic and eukaryotic).

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