Prokaryotes vs. Eukaryotes: Cell Structure, Function & Differences

Posted on Feb 20, 2025 in Biology

Eukaryotes vs. Prokaryotes

  • Organelles:
    • Unique to Prokaryotes:
      • Nucleoid: Region containing genetic material (DNA), lacks a membrane. Allows for rapid gene expression.
      • Cell Wall: Provides structural support, protects against osmotic pressure changes, and helps maintain cell shape. Composition varies among bacteria (peptidoglycan in most).
      • Plasmid: Small, circular DNA molecule separate from the chromosomal DNA. Often carries accessory genes, like antibiotic resistance. Facilitates horizontal gene transfer.
    • Common in Bacteria:
      • Flagella: Long, whip-like appendages enabling movement. Rotates like a propeller, allowing bacteria to swim toward favorable environments or away from harmful ones.
      • Pilus/Fimbriae: Hair-like appendages facilitating attachment to surfaces or other cells. Important for biofilm formation and bacterial conjugation.
  • Gene Transfer:
    • Methods in Bacteria:
      • Conjugation: Direct transfer of genetic material between bacterial cells through physical contact facilitated by sex pili. Enables exchange of plasmids, contributing to genetic diversity and antibiotic resistance.
      • Transduction: Transfer of DNA from one bacterium to another by viruses (bacteriophages) that infect bacteria. Can introduce new genes into bacterial populations.
      • Transformation: Uptake of foreign DNA from the environment, integrated into the bacterial genome. Allows bacteria to acquire new traits, such as antibiotic resistance.
  • Staining and Shapes:
    • Staining helps differentiate bacteria based on cell wall composition and morphology. Shapes (cocci, bacilli, spirilla) aid in identification and classification of bacteria.
  • Antibiotics:
    • Target specific bacterial structures or functions, such as cell wall synthesis, protein synthesis, or DNA replication.
    • Exploit differences between bacterial and eukaryotic cells to minimize harm to human cells.

Unicellular vs. Multicellular

  • Unicellular (Bacteria):
    • Must perform all essential life functions independently.
    • Rapid reproduction allows for adaptation to diverse environments.
    • Exhibit a wide range of metabolic capabilities.
  • Multicellular (Eukaryotes):
    • Cells specialize in specific functions, leading to division of labor.
    • Coordination and communication between cells enable complex organismal functions.
    • Developmental processes lead to cell differentiation and tissue formation.

Gene Transformation

  • Advantages in Bacteria:
    • Asexual reproduction facilitates rapid dissemination of advantageous traits.
    • Horizontal gene transfer mechanisms (conjugation, transduction, transformation) increase genetic diversity and promote bacterial adaptation.

Prokaryotic Cell Structure and Function

  • Prokaryotic Cell Structure:
    • Cytoplasm contains ribosomes, enzymes, and nucleoid.
    • Lack membrane-bound organelles.
    • Capsule or slime layer surrounds some bacteria, aiding in protection and attachment.
    • Some possess endospores, allowing survival in harsh conditions.
  • Metabolism:
    • Diverse metabolic pathways enable adaptation to various environments.
    • Anaerobic and aerobic respiration, fermentation, and photosynthesis are common metabolic processes.
  • Bacterial Growth:
    • Binary fission is the primary mode of reproduction.
    • Generation time varies among species and environmental conditions.
  • Ecological Roles:
    • Bacteria play crucial roles in nutrient cycling, decomposition, and symbiotic relationships.

Some bacteria are pathogens, causing diseases in plants, animals, and humans.