Structure and Functions of Prokaryotic and Eukaryotic cells | Structure and Functions of Prokaryotic Cells | Structure and Functions of Eukaryotic Cells | University Notes | Physics Notes | B.Sc. Zoology Notes by Study Buddy Notes

Structure and Functions of Prokaryotic and Eukaryotic cells

Cells are the basic units of life, and they can be broadly classified into two categories: prokaryotic and eukaryotic cells. Prokaryotic cells are simple, unicellular organisms that lack a nucleus and membrane-bound organelles, while eukaryotic cells are more complex and can be unicellular or multicellular, containing a defined nucleus and various organelles. Understanding the structure and functions of these cells is essential for studying biological processes and the diversity of life on Earth.

Structure and Functions of Prokaryotic Cells

Structure and Functions of Prokaryotic Cells

Prokaryotic cells are typically 0.1 to 5 micrometers in size and consist of several key components:

• Cell Membrane: A phospholipid bilayer that regulates the movement of substances in and out of the cell.
• Cytoplasm: A gel-like substance where metabolic processes occur, containing enzymes, nutrients, and ribosomes.
• Nucleoid Region: Contains a single, circular chromosome of DNA that is not enclosed by a membrane.
• Ribosomes: Smaller (70S) than eukaryotic ribosomes, involved in protein synthesis.
• Cell Wall: A rigid structure composed mainly of peptidoglycan (in bacteria), providing shape and protection.
• Capsule: A protective outer layer found in some bacteria, aiding in adherence and evasion of the immune response.
• Flagella and Pili: Structures that facilitate movement (flagella) and attachment to surfaces (pili).

Functions of prokaryotic cells include reproduction through binary fission, diverse metabolic processes (e.g., photosynthesis, nitrogen fixation), and genetic exchange via horizontal gene transfer.

Structure and Functions of Eukaryotic Cells

Structure and Functions of Eukaryotic Cells

Eukaryotic cells are larger (10 to 100 micrometers) and have a more complex structure, including:

• Nucleus: A membrane-bound organelle that houses linear DNA organized into chromosomes, controlling cellular functions.
• Nuclear Envelope: A double membrane with nuclear pores for transporting molecules in and out of the nucleus.
• Cytoplasm: The area between the cell membrane and nucleus containing organelles.
• Organelles:
  • Ribosomes (80S): Sites of protein synthesis.
  • Endoplasmic Reticulum (ER): Rough ER (with ribosomes) synthesizes proteins, while Smooth ER synthesizes lipids.
  • Golgi Apparatus: Modifies and packages proteins and lipids for transport.
  • Mitochondria: The powerhouse of the cell, generating ATP through cellular respiration.
  • Chloroplasts: Present in plants, involved in photosynthesis.
  • Lysosomes: Contain digestive enzymes for waste breakdown.
  • Peroxisomes: Involved in lipid metabolism and detoxification.
• Cell Membrane: Similar to prokaryotic cells, composed of a phospholipid bilayer.
• Cytoskeleton: A network of protein filaments providing structural support and aiding in intracellular transport.

Functions of eukaryotic cells include reproduction through mitosis and meiosis, specialized functions depending on cell type, and compartmentalization of cellular processes through organelles.

Differences Between Prokaryotic and Eukaryotic Cells

The primary differences between prokaryotic and eukaryotic cells can be summarized as follows:

Feature	Prokaryotic Cells	Eukaryotic Cells
Nucleus	No true nucleus (nucleoid region)	True nucleus with nuclear membrane
Size	Smaller (0.1 - 5 µm)	Larger (10 - 100 µm)
Organelles	Lack membrane-bound organelles	Membrane-bound organelles present
DNA Structure	Circular DNA	Linear DNA organized into chromosomes
Ribosomes	Smaller (70S)	Larger (80S)
Cell Wall	Peptidoglycan in bacteria	Cellulose in plants, chitin in fungi
Reproduction	Asexual (binary fission)	Asexual (mitosis) and sexual (meiosis)
Cytoskeleton	Absent or rudimentary	Well-developed cytoskeleton
Examples	Bacteria and Archaea	Plants, animals, fungi, and protists

Conclusion

In conclusion, prokaryotic and eukaryotic cells exhibit distinct structural features and functions that reflect their complexity and roles in the ecosystem. Prokaryotic cells are simpler and primarily unicellular, while eukaryotic cells are more complex, capable of forming multicellular organisms with specialized functions. Understanding these differences is fundamental to the study of biology, as they highlight the diversity of life and the evolutionary processes that have shaped living organisms.