Cell Structure and Function: Prokaryotic vs. Eukaryotic Cells

Chapter 3: The Cell

Introduction to Cell Structure and Function

This chapter explores the fundamental differences and similarities between prokaryotic and eukaryotic cells, focusing on their structure and function. Understanding these distinctions is essential for microbiology, as it underpins the classification, physiology, and behavior of microorganisms.

Comparing Prokaryotic and Eukaryotic Cells

Definitions and Origins

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

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

Classification Overview

• Prokaryotes include Bacteria and Archaea.

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

Key Differences Between Prokaryotic and Eukaryotic Cells

• 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); eukaryotic cells are larger (10–100 μm).

• Organelles: Prokaryotes do not have membrane-bound organelles; eukaryotes possess 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); eukaryotic cell walls (in plants and fungi) contain cellulose or chitin.

Similarities Between Prokaryotic and Eukaryotic Cells

• Both contain DNA as genetic material.

• Both have ribosomes for protein synthesis (though differing in size and complexity).

• Both possess cytoplasm and a plasma membrane.

Examples and Applications

• Prokaryotes: Escherichia coli (bacterium), Halobacterium (archaeon).

• Eukaryotes: Saccharomyces cerevisiae (yeast), Paramecium (protist), Arabidopsis thaliana (plant).

Table: Comparison of Prokaryotic and Eukaryotic Cells

Feature	Prokaryotic Cells	Eukaryotic Cells
Nucleus	No (nucleoid region)	Yes (membrane-bound)
Chromosomes	Single, circular	Multiple, linear
Cell Size	0.2–2.0 μm	10–100 μm
Organelles	Absent	Present
Cell Wall	Peptidoglycan (bacteria)	Cellulose (plants), chitin (fungi)
Division	Binary fission	Mitosis/meiosis

Additional info: The images provided show typical prokaryotic and eukaryotic cell ultrastructure, highlighting differences in internal organization and complexity. These visual aids are useful for understanding the spatial arrangement of cellular components.