Cells Eukaryotes and Prokaryotes

From CellBiology

Life - Eukaryotes and Prokaryotes


Bacteria - Escherichia coli

Movie - Neutrophil chasing Bacterium


This current page is the science lecture Medicine Foundations 2016 Lecture Link

This lecture introduces the cell as the unit of life. Firstly, by the methods we use to see cells and biological structures and what we consider to be "alive". Then by looking at major differences between cell types and their organisation as unicellular or multicellular organisms. Finally, the presence or absence of a nucleus which is the definition of the major 2 classes of cells.

(Greek, Karyose = kernel, as in a kernel of grain)

2017 Lecture PDF

Lecture Archive: 2016 PDF | 2014 | 2013 | 2012 | 2012 iLecture | 2009 iLecture | 2009 Cell Types | 2008 Cell Types


  • Introduction to biological molecules
  • Understand the dimensions cells
  • Understand differences between prokaryotes and eukaryotes
  • Understand differences between unicellular and multicellular organisms
  • Brief understanding of viruses and prions

About Human Body

Human Cells

  • 210+ cell types in body
  • total number of estimated cells in the body - 1013 (American Ten trillion/British Ten billion)


  • bacteria, fungi and archaea
    • fungi are eukaryotes (include yeasts and molds)
  • found on all surfaces exposed to the environment
    • skin and eyes, in the mouth, nose, small intestine
  • most bacteria live in the large intestine
  • 500 to 1000 species of bacteria live in the human gut
  • total number of estimated flora ten times as many bacteria 1014 (American One hundred trillion/British One hundred billion)

Cell Sizes

Salamander egg (oocyte)
  • frog or fish egg are the largest individual cells easily visible, approx 1+ mm diameter
  • human or sea urchin egg, approx 100 micron (µm) diameter
  • typical somatic cell, approx 20 micron diameter
  • plant cells are larger, approx 30 x 20 micron
  • bacteria are smaller, approx 2 x 1 micron

Divisions of Life

Time scale of evolution


Archaea - Halobacteria.jpg

Archaea (Halobacteria)


File:Leukocyte phagocytosis of yeast
  • animals
  • plants
  • fungi (yeast, unicellular)
  • protists (not animals, plants or fungi)

Textbook Links: The Origin and Evolution of Cells | MBoC -Divisions of Life

Unicellular and Multicellular

  • Unicellular
    • All prokaryotes and some eukaryotes
      • Yeast + budding, non-budding
      • Protozoa + classified by means of locomotion: flagellates, amoeboids, sporozoans, ciliates + often "feed" on bacteria

Amoeba feeding on a bacteria (Legionella pneumophila)

  • Multicellular
    • Eukaryotes
    • Plants and Animals
    • Allowed development of specialized cells
    • functions and tissues


Escherichia coli.jpg

Escherichia coli bacteria

Gram-positive Micrococcus luteus bacteria.jpg

Micrococcus luteus bacteria

Bacteria morphology.png

Bacteria morphology

  • evolutionarily arose first (3.5 billion years ago) Evolution of Cells
  • bacteria are smaller, approx 2 x 1 micron (1x10-6 m)
  • not all bacteria are dangerous or disease causing

(MH - the adult human in addition bacteria to the skin surface and lining of the respiratory/digestive tract, also has intestines contains trillions of bacteria made up from hundreds of species and thousands of subspecies)

  • biochemically diverse
  • simple structure, classified by shape (rod-shaped, spherical or spiral-shaped)
  • some prokaryotic cells have also been shown to have a "cytoskeleton", which is different from eukaryotic cells.
Bacterial morphologies

Bacteria morphology.png

Bacteria morphology

Prokaryote Membrane

Common to Eukaryote

  • lipid bilayer - containing protein and phospholipid (about 3:1)
  • lipid rafts - stabilised membrane regions containing flotillins
    • scaffolding proteins for processes - signalling, endo- and exocytosis, transport, protein translocation and cell division

Surface Specializations

  • Flagella - flagella of motile bacteria differ in structure from eukaryotic flagella.
    • A basal body anchored in the plasma membrane and cell wall gives rise to a cylindrical protein filament (3 to 12 µm long, 12 to 30 nm in diameter).
    • The flagellum moves by whirling about its long axis.
    • The number and arrangement of flagella on the cell are clinically diagnostically useful.
  • Pili - (Fimbriae) slender, hair-like, proteinaceous appendages on the surface of many (Gram-negative) bacteria.
    • required for adhesion to host surfaces.
    • more rigid in appearance than flagella
  • Capsules - lies outside the cell wall, thick (up to 10 µm) outer capsule of high-molecular-weight, viscous polysaccharide ge
    • others have more amorphous slime layers.
    • Capsules confer resistance to phagocytosis.

Prokaryotic Motility

Some bacteria are highly motile and there are differing mechanisms of motility.

Bacterial flagella cartoon.jpg
Bacteria motility movie 1.jpg
 ‎‎Bacteria Motility
Page | Play
flagella motility spiral bacteria

Prokaryotes Cell Wall

Prokaryote cell cartoon
  • Bacterial Shape - Bacterial shapes and cell-surface structures
  • Bacterial Membranes - A small section of the double membrane of an E. coli bacterium
    • Bacterial outer membranes - outer membrane contains porins
  • Bacterial cell walls - Bacterial cell walls
    • Gram-negative bacteria surrounded by a thin cell wall beneath the outer membrane
    • Gram-positive bacteria lack outer membranes and have thick cell walls

(MH - note that some unicellular eukaryotes can also have a cell wall)

  • Antibiotics - inhibit either bacterial protein synthesis or bacterial cell wall synthesis Antibiotic targets Gram-positive and Gram-negative bacteria

Prokaryote Genetics

  • multiple copies of circular DNA within the cytoplasm
  • DNA -> RNA - ribosomes immediately can attach to RNA
  • genes have no introns
  • prokaryotic genome
  • Epigetics - DNA methylation and restriction enzymes act to protect the integrity of prokaryotic genomes. PLoS
    • restriction enzymes target foreign DNA for cleavage
    • DNA methylation protects the host genome from destruction

iBiology video: Prokaryotic Vs Eukaryotic Transcription

Prokaryote Division

E. coli FtsZ
Bacteria cell division 1.jpg
 ‎‎Bacteria Division
Page | Play
Bacteria cell division 2.jpg
 ‎‎Bacteria Division
Page | Play

Prokaryote Mycoplasmas

Mycoplasma hominis infected Hela cells
  • smallest self-replicating organisms
  • smallest genomes (approx 500 to 1000 genes)
  • spherical to filamentous cells
  • no cell walls
  • surface parasites of the human respiratory and urogenital tracts
    • Mycoplasma pneumoniae infect the upper and lower respiratory tract
    • Mycoplasma genitalium a prevalent sexually transmitted infection
    • Mycoplasma hominis associated with bacterial vaginosis and pelvic inflammatory disease
    • Mycoplasma hyorhinis found in patients with AIDS

Prokaryote "Cytoskeleton"

Prokaryotic and eukaryotic cytoskeleton 01.jpgProkaryotic and eukaryotic cytoskeleton 02.jpg

  • FtsZ - (Filamenting temperature sensitive mutant Z) homologue of tubulin
  • MreB - homologue of actin, essential for cell-shape maintenance in non-spherical bacteria PMID 14982627

Prokaryotic and Eukaryotic Cells

The following links describe the major differences between prokaryotic and eukaryotic cells, the way they divide and the way in which antibiotics have their action on prokaryotic cells.

Plant Cell

Plant Cell cartoon
Plant Plastid types
  • plant cells are larger than mammalian cells approx 30 x 20 micron
  • Additional Organelles
  • Central Vacuole
    • tonoplast maintains cell's turgor
    • storage (water, ions, and nutrients such as sucrose and amino acids, and waste products)
  • Plastids
    • organelles found in plants and algae
    • chloroplasts for photosynthesis
    • Amyloplasts for starch storage
    • Chromoplasts for pigment synthesis and storage
    • Leucoplasts - can differentiate into more specialized plastids (Amyloplasts - starch storage, Elaioplasts - storing fat, Proteinoplasts - storing and modifying protein)
    • (MH - plastids and mitochondria and have own DNA)
  • Cell Wall
    • Rigid structure outside cell membrane
    • No ability to move
    • Resist osmotic stresses
    • Structure - cellulose, hemicellulose, pectin
  • Specialized Adhesion Junctions
    • plasmodesmata
    • cell-cell communication pathways
    • allow cell membrane and endoplasmic reticulum of adjacent cells are continuous Plasmodesmata


  • disk-shaped and about 5-8 µm in diameter and 2-4 µm thick. A typical plant cell has 20-40 of them.
Plant organelles

Animal and Plant Cell

Plant Cell Structure.jpg


Dengue virus Herpes virus Zika virus
Dengue virus Herpes virus - CDC electron micrograph Zika virus TEM02.jpg
  • not a cell Latin, virus = toxin or poison
  • not alive
  • infects living cells
  • unable to grow or reproduce outside a host cell
  • Infect different hosts (animal, plant and bacterial)
  • Classified
    • RNA or DNA viruses
    • double or single stranded


  • contains the genetic material, DNA or RNA
  • within a protective protein coat (capsid)


  • A virus that infects bacteria


VCJD brain
  • not alive
  • an infectious prion protein
  • misfolded normal protein (three-dimensional structure)
  • can form aggregates
  • Types
    • Creutzfeldt-Jacob disease (CJD) and Kuru a human neural prion disease
    • Bovine spongiform encephalopathyvery (BSE) in cattle, "mad cow disease"
    • Scrapie in sheep

Biological Levels

  • Whole cell
  • Organelles (nucleus, mitochondria, ER, Golgi)
  • Components
  • Biological polymers (chains of molecules, consisting of monomer subunits)
    • DNA, RNA, Protein, sugars, cellulose
  • Organic molecules (monomer subunits)
    • nucleotides, amino acids, carbohydrate

Eukaryotic Cell Organelles

  • Fundamental concept - all cells
    • Specialized exceptions
  • Organelle
  • specialized part of a cell that has its own particular function
  • Membrane bound (enclosed)
  • forms "compartments" within the cell

Next Lecture

  • Cell Compartments and Membranes
    • Metabolic and biochemical “specialization”
    • Localization of function
    • Import and export
    • Regulation of transport
    • Detection of signals
    • Cell-cell communication
    • Cell Identity
    • Cell membrane - plasma membrane, plasmalemma
    • Organelle membranes - basic structure similar



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External Links

2017 Course Content


Lectures: Cell Biology Introduction | Cells Eukaryotes and Prokaryotes | Cell Membranes and Compartments | Cell Nucleus | Cell Export - Exocytosis | Cell Import - Endocytosis | Cytoskeleton Introduction | Cytoskeleton - Microfilaments | Cytoskeleton - Microtubules | Cytoskeleton - Intermediate Filaments | Cell Mitochondria | Cell Junctions | Extracellular Matrix 1 | Extracellular Matrix 2 | Cell Cycle | Cell Division | Cell Death 1 | Cell Death 2 | Signal 1 | Signal 2 | Stem Cells 1 | Stem Cells 2 | Development | 2017 Revision

2017 Laboratories: Introduction to Lab | Fixation and Staining |

2017 Projects: Group 1 - Delta | Group 2 - Duct | Group 3 - Beta | Group 4 - Alpha

Dr Mark Hill 2015, UNSW Cell Biology - UNSW CRICOS Provider Code No. 00098G