Module 1

• Prokaryote

  A microscopic single-celled organism that lacks a nucleus and other membrane-bound organelles
• Prokaryotes

  Includes organisms in the domains:

  • Bacteria
  • Archaea
• Prokaryotic Structures

  All prokaryotes have:

  • Cell membrane
  • Cell wall (peptidoglycan)
  • Cytoplasm
  • Ribosomes
  • Nucleoid (single circular chromosome)

  Most prokaryotes also have:

  • Plasmids
  • Pilli
  • Flagellum
• Pilli (Pilus)

  Tiny hair-like structures on the surface of a cell, used for injecting plasmids into other bacteria
• Plasmids

  Tiny extra-chromosomal loops of DNA
• Flagella (Flagellum)

  Hair-like extensions, used for propelling the bacteria through a fluid
• Cell Shapes

  Bacillus - rod-shaped

  Coccus - spherical, round-shaped

  Spirillum - spiral, twisted-shaped

  Spirochaete - long spiral-shaped

  Vibrio - boomerang-shaped
• Cell Arrangement

  Some bacteria exist individually, others in pairs (diplo-), long chains (strepto-), and bunches (staphylo-)
• Chemical Composition

  Gram-positive bacterium:

  • Cytoplasm
  • Cell membrane
  • Periplasm
  • Cell wall

  Gram-negative bacterium:

  • Cytoplasm
  • Cell membrane
  • Periplasm
  • Cell wall
  • Periplasm (2nd layer)
  • Cell membrane (2nd layer)
• Eukaryote


  An organism consisting of a cell or cells in which is there is a distinct membrane-bound nucleus and organelles
• Eukaryotes

  Includes organisms in the domain:

  • Eukarya

  Examples:

  • Animals
  • Plants
  • Fungi
  • Algae
• Eukaryotic Structures

  These include:

  • Nucleus (membrane-bound)
  • Nucleolus
  • Mitochondria
  • Endoplasmic Reticulum
  • Cytoplasm
  • Ribosomes
  • Golgi appartus
  • Lysosome
• Eukaryotic Structures (Plant Cells)


  Plant cells contain:

  • Large vacuole
  • Cellulose cell wall
  • Plasmodesmata

  Many also contain:

  • Plastids (including chroloplasts)

  None of these are found in animal or fungal cells.
• Eukaryotic Structures (Fungal Cells)

  Fungal cells contain:

  • Centrioles (paired barrel-shaped organelles, organising the spindles during cell division)
  • Chitin cell wall
• Eukaryotic Structures (Animal Cells)


  Animal cells contain:

  • Centrioles (paired barrel-shaped organelles, organising the spindles during cell division)

  This feature is typically absent in plant cells. However, animal cells do not have a cell wall unlike plant and fungal cells
• Cell Variety

  Many eukaryotes are:

  • Multicellular
  • Allows for cell specialisation (large variety of cell types and structures, even within a single multicellular organism)

  Examples:

  • Nerve cells
  • Blood cells
• Microbiology

  The branch of biology dealing with the structure and function of microscopic organisms.
• Types of Microscopes

  • Light microscopes
  • Electron microscopes
• Light Microscope

  Works by passing light through the specimen. The light is then magnified by lenses (bottom stage -> objective -> subjective)
• Advantages of Light Microscope

  • Less expensive, making them more accessible to many laboratories and educational institutions
  • Easy to operate and maintain, requiring minimal training for users
  • Short time required to set up
  • Samples can be living or dead
  • Portable
• Disadvantages of Light Microscope

  • Poor resolution at high magnification
  • Depth of field can be limited
  • Maximum magnification of 1000x
  • Obtaining high contrast images can be difficult
  • Restricted to visible light spectrum
• Light Microscope

  Allows for researchers to observe samples in real-time, providing dynamic information about cellular processes and interaction
• Types of Electron Microscopes

  • Transmission Electron Microscope (TEM)
  • Scanning Electron Microscope (SEM)
• Electron Microscope

  Works by passing a beam of electrons through a specimen. The electrons are detected by a sensor, which projects an image onto a screen
• Transmission Electron Microscope (TEMs)


  Works by firing a beam of electrons through a very thinly sliced specimen, within a strong magnetic field that acts as a lens, and produces a very high definition, 2D cross-section.
• Advantages of TEMs

  • High resolution
  • Maximum magnification of 5,000,000x
  • Can produce high-contrast images
• Disadvantages of TEMs:

  
  

  • More expensive, making them less accessible to many laboratories and education institutions
  • Relatively long time required to set up
  • Samples must be dead (vacuum environment)
• Specimen Preparation (TEM)

  Dead, Fixed, Dehydration, Embedded
• Transmission Electron Microscope (TEMs)

  Allow researchers to see internal cellular structures including organelles, membranes and macromolecules in more detail.
• Scanning Electron Microscope (SEMs)

  Electrons are fired from different angles, bouncing off the surface of a specimen and produce an image that shows the topography of the surface.
• Advantages of SEMs

  • High resolution
  • Easy specimen preparation
  • Can produce detailed 3D images of samples
• Disadvantages of SEMs

  • Expensive
  • Long time required to set up
  • Samples must be dead (vacuum environment)
• Specimen Preparation (SEM)


  Dead, Fixed, Dehydration and Mounted on a Stub
• Structures (Light Microscope, TEM and SEM)

  Organelles that can be observed:

  
  

  Light Microscope

  • Chloroplasts
  • Nucleus
  • Vacuole

  Transmission Electron Microscope

  • Mitochondria
  • Endoplasmic Reticulum
  • Ribosomes

  Scanning Electron Microscope

  
  

  None, only the outline can be observed
• Biological Drawing


  A drawing made in a practical session to record first hand observations.
• Organelle


  A membrane-bound structure within an eukaryotic cell, which performs a specialised function
• Nucleus

  • Large, double membrane-bound organelle
  • Contains nuclear pores, which allows things in and out of the nucleus (most notably RNA)
  • Contains most of the cell's DNA (genetic information)

  Function: To control the activities of the cell by determining which proteins will by synthesised by ribosomes
• Nucleolus

  • Dark area observed within the nucleus

  Function: Where ribosomal RNA is synthesised, for the production of new ribosomes
• Ribosomes

  • Made up of ribosomal RNA and protein

  Function: Site of protein synthesis
• Endoplasmic Reticulum

  • Networks of membrane-bound sacs
  • Two kinds of ER: Rough and smooth
  • Rough ER has ribosomes attached to it, while smooth ER does not

  Function: Allowing materials to be transported throughout the cell. Rough ER is involved in transporting proteins, whereas smooth ER is involved in the transport of other compounds such as lipids.