Prokaryotic cell 17022025 Lecture 3_f268a6f4d1fd9db35adeb568fec0eecd

Recommended Books

• Editors: Steven R. Goodman, C.L. Lundell (The University of Texas at Dallas)

• Professor of Life Sciences and Cell Biology

Course Information

• Duration: 45 Minutes

• Subject: Cell Biology (Prokaryotic Cell)

• Instructor: Dr. Nompumelelo Mkhwanazi, PhD (Virology)

Content Overview

Key Concepts

• Differences:

  • Prokaryotic vs. Eukaryotic Cells

  • Archaebacteria vs. Eubacteria

  • Gram-positive vs. Gram-negative Bacteria

• Prokaryotic Cell Structure:

  • Organelles

  • Respiration

  • Genetic Material

  • Mesosomes

• Review Questions:

  • Bacterial cell wall structure

  • Components of prokaryotic cell wall

  • Types of archaebacteria

  • Differences between Gram-positive and Gram-negative bacteria

  • Prokaryotic genetic material

Historical Overview

• First observed by Robert Hooke (1665)

• Cells are the fundamental units of life

• New cells arise from division of existing cells

Prokaryotic Cell Structure

Definition

• Prokaryotes: Unicellular organisms lacking membrane-bound nuclei and organelles.

Size

• Ranges from 0.05 µm to 600 x 80 µm.

• Smaller cells have an increased surface area relative to volume, enhancing transport rates and growth.

Cell Morphology

Shapes of Prokaryotes

• Cocci: Spherical

• Bacilli: Rod-shaped

• Filamentous: Multinucleate filaments

• Spirilla: Rigid spirals

• Spirochetes: Flexible spirals

• Pleomorphic: Variable shapes

Cell Organization

• Components:

  • Cytoplasm

  • Plasma Membrane

  • Periplasmic Space

  • Cell Wall

  • Slime Layer/Capsule

  • Flagella/Pili

Cytoplasm

• Contains:

  • Water and various components

  • Ribosomes (protein synthesis)

  • Inclusion bodies (organic/inorganic granules)

Plasma Membrane

Structure

• Phospholipid bilayer with proteins.

Functions

• Retains cytoplasm, selective permeability, nutrient and waste transport, energy generation, and receptor proteins for signaling.

Archaebacteria and Eubacteria

Characteristics

• Archaebacteria:

  • Ancient, thrive in extreme environments (acidic, high heat).

  • Different cellular components compared to Eubacteria.

  • Major groups: Methanogens, Halophiles, Thermophiles.

• Eubacteria: Common bacteria in neutral conditions.

Scientific Differences

• Archaeal membranes use isoprenoids, ether linkages, and sometimes monolayers.

• No complex internal membranes; presence of mesosomes (membrane invaginations).

Cell Wall Structure

General Info

• Provides shape and protection from osmotic lysis.

• Virulence factors may include LPS in Gram-negative bacteria.

Differences between Gram-Positive and Gram-Negative

• Gram-positive: Thick peptidoglycan, teichoic acids.

• Gram-negative: Thin peptidoglycan, outer membrane, periplasmic space, LPS.

Nucleoid and Plasmids

Nucleoid

• Contains a circular double-stranded DNA, without a nuclear membrane.

Plasmids

• Circular, double-stranded DNA, often used in genetic manipulation.

Ribosomes

• Present in all cells, serve as protein synthesis sites.

• Prokaryotic ribosomes (70S) differ from eukaryotic ribosomes (80S).

Fimbriae/Pili

Structure and Functions

• Projections aiding in surface attachment.

• Types: Ordinary pili (host adherence) and sex pili (bacterial conjugation).

Flagella

Functionality

• Enables bacterial motility.

• Composed of flagellin protein subunits.

Conclusion

• Invitation for questions and further discussion.