• resolution is the ability of a microscope to distinguish between 2 objects that are close together

• the limiting factor of a light microscope is the wavelength of light

• the theoretical limit to resolution microscope is 20

The electron microscope

• Much better resolution

• uses a beam of electrons instead of light

• electrons have a shorter wavelength and therefore greater resolution

• resolution is 0.1m,much better than a light microscope

• there are two types of electron microscopes

• scanning electron microscope

  • produces images that are reflected from the electrons/specimen

  • also produces a 3D image /looks like a photograph

• transmission electron microscopes

  produces images from electrons that have passed through and they produce a 2D image

bacteria and blue green algae

• these type of cells are prokaryotes that are prokaryotic organisms

• cells are very small,smaller than red blood cells

• 0.1 to 10 micro meters in length

• they differ from eukaryotic cells in a number of ways

• no nucleus

• they usually have a single circular DNA molecule that acts as their chromosomes

• bacteria only have 3000 types of genes

bacteria

• in addition to the main chromosome they have much smaller loops of DNA called plasmids

• they have cell membrane and a cell wall

• they have a smaller ribosomes than eukaryotic cells (70’s rather than 80’s in eukaryotes)

• some have flagella - which differs depending on the structure of the prokaryotic cell

Eukaryotic cells

• larger than bacteria,prokaryotes

• have a nucleus with membrane

• have a membrane bound organelle within the cell

• division of labour within the cell

• each organelle has a specific function

plant cell