UNSW Cell Biology

This lecture compares the 2 major types (prokaryote, eukaryote) of cells, the differences in eukaryotes (plants, animals) and their organisation (unicellular, multicellular).

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Next Lecture: Compartments/Membranes

• 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

Bacteria - Escherichia coli (Image: CDC)

Yeast - Candida albicans (Image: CDC)

CW - cell wall, PM - plasma membrane, M - mitochondria,
V - vacuole, N - nucleus

Amoeba - Hartmannella vermiformis (Image: CDC) shows an amoeba (orange) as entrap a bacterium (green, Legionella pneumophila) with an extended pseudopod

Yeast - Candida transmission EM (Image: CDC)

Bacteria Shapes and Sizes

(MH - selected examples, note scalebars in the images below)

Escherichia coli rod-shaped, lives in the lower intestine of warm-blooded animals, most strains are harmless, but some strains cause food poisoning in humans (Image: CDC)

Micrococcus luteus spherical, Gram-positive bacteria found in environment (soil, dust, water, air) and as part of the normal flora of the mammalian skin and can colonize human mouth, mucosae, oropharynx and upper respiratory tract (Image: CDC)

Staphylococcus aureus - spherical, lives on the skin or in the nose, most common cause of staph infections(Image: CDC)

Mycobacterium tuberculosis rod-shaped,can live in the respiratory tract, slow growing bacteria which causes most cases of tuberculosis (Image: CDC)

Borrelia burgdorferi - spiral, cause of lyme disease (Image: CDC)

• plant cells are larger than mammalian cells approx 30 x 20 micron
• Additional Organelles
  • Central Vacuole
    • tonoplast maintains cell's turgor
    • storage (food, waste)
  • Plastids
    • Chloroplasts for photosynthesis
    • Amyloplasts for starch storage
    • (Mitochondria and plastids have own DNA)
• Cell Wall
  • Rigid structure outside cell membrane
  • No ability to move
  • osmotic stresses
  • cellulose, hemicellulose, pectin
• Adhesion Junctions
• plasmodesmata
• cell-cell communication pathways
• allow cell membrane and endoplasmic reticulum of adjacent cells are continuous

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

• not a cell
  • Latin, virus = toxin or poison
• 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

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

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

• 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

• 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

Next Lecture: Compartments/Membranes

Cell Membrane Model

In 2008 a new way of presenting course content online is being trialled. Please let me know of any difficulties/suggestions or things that work well.

Notice that in some slides I have added annotations in brackets with my initials (MH - )

Links: Jump-Starting a Cellular World: Investigating the Origin of Life, from Soup to Networks