Chapter 3: The Cell

Part B: Cell Structure and Function

This section introduces the fundamental differences between prokaryotic and eukaryotic cells, focusing on their structural and functional characteristics. Understanding these differences is essential for microbiology students, as it forms the basis for studying microbial diversity, physiology, and classification.

Comparing Prokaryotic and Eukaryotic Cells: An Overview

Definitions and Origins

• Prokaryote: Derived from Greek words meaning "prenucleus." Prokaryotic cells lack a true nucleus and membrane-bound organelles.

• Eukaryote: Derived from Greek words meaning "true nucleus." Eukaryotic cells possess a nucleus enclosed by a membrane and various membrane-bound organelles.

Classification and Examples

• Prokaryotes include Bacteria and Archaea.

• Eukaryotes include Protista, Fungi, Plantae, and Animalia.

Key Structural Differences

• Nucleus: Prokaryotes lack a membrane-bound nucleus; eukaryotes have a true nucleus.

• Chromosomes: Prokaryotes have a single, circular chromosome; eukaryotes have multiple, linear chromosomes.

• Cell Size: Prokaryotic cells are generally smaller (0.2–2.0 μm in diameter); eukaryotic cells are larger (10–100 μm in diameter).

• Organelles: Prokaryotes lack membrane-bound organelles; eukaryotes contain organelles such as mitochondria, endoplasmic reticulum, and Golgi apparatus.

• Cell Division: Prokaryotes divide by binary fission; eukaryotes divide by mitosis and meiosis.

• Cell Wall Composition: Prokaryotic cell walls contain peptidoglycan (in bacteria) or pseudomurein (in archaea); eukaryotic cell walls (if present) are made of cellulose (plants, algae) or chitin (fungi).

Table: Comparison of Prokaryotic and Eukaryotic Cells

Examples and Applications

• Example: Escherichia coli is a typical prokaryotic bacterium, while Saccharomyces cerevisiae (yeast) is a eukaryotic microorganism.

• Application: The distinction between prokaryotic and eukaryotic cells is crucial for antibiotic development, as many antibiotics target structures unique to prokaryotes (e.g., peptidoglycan cell wall).

Additional info: The images provided show representative prokaryotic and eukaryotic cells, highlighting differences in internal complexity and compartmentalization.