Cell Structure Revision Notes
Microscope
Magnification – how much bigger an image appears compared to the actual size of the object (e.g. 100X magnification = 100 times wider and
longer than it actually is)
Resolution – the clarity of an image: the higher the resolution the clearer the image (e.g. ability to see 2 separate organelles and not 1 blurry
object)
Optical Microscopes
-objective lens produced a magnified image which is magnified more by the eyepiece lens. Light source is often needed too.
-able to be used to study whole living specimens (Amoeba, human blood, cheek cells, animal/plant tissue)
-maximum magnification of 1500X or 2000X
-uses wavelength between 400 and 700nm (objects under 200nm will appear as one object – ribosomes cannot be seen [20nm])
-relatively cheap
-easy to use
-portable (used in the field as well as laboratories)
Laser Scanning Microscopes
-use a laser light to scan an object point to point and assemble a computer image
-high resolution and high contrast
-focus in on depths within a specimen so can be used on live specimens as well as cells
-use in medicine for swift diagnosis of fungal corneal infection
Transmission Electron Microscope
-beam of electrons pass through the specimen and focused onto a screen or photographic plate
-specimen must be dehydrated and stained with metal salts (dead)
-produces a 2D black and white image (electron micrograph)
-magnification up to X2,000,000
-uses wavelength of 0.004nm
Scanning Electron Microscope
-elections bounce off the specimen and focused onto a screen
-specimen is placed into a vacuum and stained with film of metal
-causes a 3D image which is black and white but computer programmes can add false colour
-magnification from X15 to X200 000
-uses wavelength of 0.004nm
Summary
Feature Light Microscope Transmission Electron Microscope (TEM) Scanning Electron Microscope (SEM)
Source of Image Objective lens Beam of electrons fired through specimen creating Pass a beam of electrons over the
an image. surface of the specimen forming an
image.
Maximum X1500-X2,000 X2,000,000 X15-X200,000
Magnification
Maximum resolution 200nm 0.5nm 3-10nm
Live Specimen? Yes No No
Staining Specimen Yes Dehydrated and stained with metal salts Vacuum and stained with film of metal
Cost Cheap Expensive Expensive
Microscope
Magnification – how much bigger an image appears compared to the actual size of the object (e.g. 100X magnification = 100 times wider and
longer than it actually is)
Resolution – the clarity of an image: the higher the resolution the clearer the image (e.g. ability to see 2 separate organelles and not 1 blurry
object)
Optical Microscopes
-objective lens produced a magnified image which is magnified more by the eyepiece lens. Light source is often needed too.
-able to be used to study whole living specimens (Amoeba, human blood, cheek cells, animal/plant tissue)
-maximum magnification of 1500X or 2000X
-uses wavelength between 400 and 700nm (objects under 200nm will appear as one object – ribosomes cannot be seen [20nm])
-relatively cheap
-easy to use
-portable (used in the field as well as laboratories)
Laser Scanning Microscopes
-use a laser light to scan an object point to point and assemble a computer image
-high resolution and high contrast
-focus in on depths within a specimen so can be used on live specimens as well as cells
-use in medicine for swift diagnosis of fungal corneal infection
Transmission Electron Microscope
-beam of electrons pass through the specimen and focused onto a screen or photographic plate
-specimen must be dehydrated and stained with metal salts (dead)
-produces a 2D black and white image (electron micrograph)
-magnification up to X2,000,000
-uses wavelength of 0.004nm
Scanning Electron Microscope
-elections bounce off the specimen and focused onto a screen
-specimen is placed into a vacuum and stained with film of metal
-causes a 3D image which is black and white but computer programmes can add false colour
-magnification from X15 to X200 000
-uses wavelength of 0.004nm
Summary
Feature Light Microscope Transmission Electron Microscope (TEM) Scanning Electron Microscope (SEM)
Source of Image Objective lens Beam of electrons fired through specimen creating Pass a beam of electrons over the
an image. surface of the specimen forming an
image.
Maximum X1500-X2,000 X2,000,000 X15-X200,000
Magnification
Maximum resolution 200nm 0.5nm 3-10nm
Live Specimen? Yes No No
Staining Specimen Yes Dehydrated and stained with metal salts Vacuum and stained with film of metal
Cost Cheap Expensive Expensive
