Resolution :  principles and applications of science

• 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