Functional Anatomy of Prokaryotic and Eukaryotic Cells: Comparative Study Notes

Chapter 4: Functional Anatomy of Prokaryotic and Eukaryotic Cells

Introduction

This chapter explores the structural and functional differences between prokaryotic and eukaryotic cells, which are foundational concepts in microbiology. Understanding these differences is essential for studying microbial physiology, taxonomy, and the mechanisms of disease.

Two Kinds of Cells

Classification of Cellular Life

• Prokaryotes include Bacteria and Archaea.

• Eukaryotes include Animals, Plants, Algae, Fungi, and Protozoa.

• No known multicellular organisms are prokaryotic.

	Prokaryotes	Eukaryotes
Multicellular Organisms	None Known	Eukarya: Animals, Plants
Microorganisms	Archaea, Bacteria	Eukarya: Algae, Fungi, Protozoa

Cell Structure Overview

Prokaryotic vs. Eukaryotic Cells

The term prokaryote derives from Greek for "prenucleus," while eukaryote means "true nucleus." The following diagram highlights the major internal structures of each cell type.

• Prokaryotic cells lack a membrane-bound nucleus and organelles.

• Eukaryotic cells possess a nucleus and various membrane-bound organelles.

Key Differences Between Prokaryotic and Eukaryotic Cells

Genetic Material and Organization

• Prokaryotes:

  • DNA not enclosed in a nuclear membrane.

  • Single, circular chromosome.

  • DNA not associated with histone proteins.

  • No membrane-enclosed organelles.

  • Cell wall complex (if present).

• Eukaryotes:

  • DNA enclosed in a nuclear membrane.

  • Multiple, linear chromosomes.

  • DNA associated with histones and non-histone proteins.

  • Membrane-enclosed organelles present (e.g., Golgi complex, mitochondria, lysosomes).

  • Cell wall, if present, is very simple.

Additional info:

• Histones are proteins that help package and organize DNA in eukaryotes, but are absent in prokaryotes.

• Organelles are specialized structures within eukaryotic cells that perform distinct functions (e.g., energy production, protein synthesis).

Summary Table: Prokaryotic vs. Eukaryotic Cells

Feature	Prokaryotes	Eukaryotes
Nucleus	Absent	Present
DNA Form	Circular, single chromosome	Linear, multiple chromosomes
Histones	Absent	Present
Organelles	Absent	Present
Cell Wall	Complex (if present)	Simple (if present)

Key Terms

• Prokaryote: A unicellular organism lacking a true nucleus and membrane-bound organelles.

• Eukaryote: An organism whose cells contain a nucleus and membrane-bound organelles.

• Histone: Protein associated with DNA packaging in eukaryotes.

• Organelle: Specialized subunit within a cell with a specific function.

Example

• Bacteria (e.g., Escherichia coli) are prokaryotes.

• Yeast (e.g., Saccharomyces cerevisiae) is a eukaryote.