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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.