2009 Lecture 2

From CellBiology
Bacteria - Escherichia coli

Life - Eukaryotes and Prokaryotes


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.

Dr Mark Hill (2009)

Lecture Audio

The University has a system for automated recording of lectures called Lectopia. Lectopia requires login using your student number and unipass. I will be adding the link to each iLecture Audio following the Lecture. Due to the automated recording method, most lectures begin 4-5 minutes into MP3 recordings and occasionally stop before the end of the lecture. 2009 All Audio Files

Lecture 2: Cells Eukaryotes and Prokaryotes Lecture Date: 11-03-2009 Lecture Time: 10:00 Venue: BioMed E Speaker: Mark Hill

Next Lecture: Cell Membranes and Compartments


MH - note that content listed below will not match exactly current lecture structure but has been selected as having similar content.


  • 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


Last year's lecture 2008 Lecture 2

Cell Sizes

  • frog or fish egg are the largest individual cells easily visible, approx 1mm 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

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


Prokaryote cell cartoon
  • evolutionarily arose first (3.5 billion years ago)
  • 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)

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

Prokaryotes Cell Wall

  • 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
  • Bacterial Replication - DNA replication and cell division in a prokaryote

Prokaryote Mycoplasmas

  • 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

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

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


Herpes virus - CDC electron micrograph
  • 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)


  • 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,
  • 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



Search Online Textbooks


  • CellsBenjamin Lewin, Lynne Cassimeris, Vishwanath R. Lingappa, M.D., George Plopper Jones & Bartlett Publishers, 2007
  • Plant Cell Vacuoles By Deepesh Narayan De, CSIRO (Australia)



Internal Links

External Links

2009 Course Content


Cell Biology Introduction | Cells Eukaryotes and Prokaryotes | Cell Membranes and Compartments | Cell Nucleus | Cell Export - Exocytosis | Cell Import - Endocytosis | Cell Mitochondria | Cell Junctions | Cytoskeleton Introduction | Cytoskeleton 1 Intermediate Filaments | Cytoskeleton 2 Microtubules | Cytoskeleton 3 Microfilaments | Extracellular Matrix 1 | Extracellular Matrix 2 | Cell Cycle | Cell Division | Cell Death 1 | Cell Death 2 | Signal 1 | Signal 2 | Stem Cells | Stem Cells | Development | Revision


Introduction to Lab | Microscopy Methods | Preparation/Fixation | Immunochemistry | Cell Knockout Methods | Cytoskeleton Exercise | Confocal Microscopy | Tissue Culture 1 | Tissue Culture 2 | Microarray Lab visit

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