Magnification, Resolution and Illumination

Cell Biology: Magnification and Illumination

Let's take a look at the secret life inside our cells...

How large are cells?Let's put things into perspective....

Size is relative….Organism Size

Prokaryotic cell 1 – 10 μmAnimal Cell 10 – 30 μmPlant Cell 10 – 100 μm

Virus < 100 ηmDNA molecule 2 ηmPhospholipid membrane

10 ηm

Is magnification all that matters?Magnification versus Resolution

Is there a limit to magnification?Does magnification improve resolution?Resolution of a microscope is its ability to separate small

objects which are cose togetherResolution is determined by light/(electron) wavelength;

the shorter the wavelength, the higher the resolutionLight microscope resolution is 0.2 μmElectron microscope resolution is 1 ηmScanning Tunnel microscope resolution is 0.01 ηm

length 0.01 ηm depth

Light microscope: Magnification

Normal maximum

magnifications of ocular and

objective lenses are 10X and

100X respectively, giving overall

maximal magnification of

X 1000

Why do modern microscope images look so beautiful?

Modern Illumination techniques used in light microscopy

These techniques modify the light path to generate improved contrast: Phase contrast micrcoscopy Cross-polarised (confocal) light microscopy Dark field microscopy Fluorescent microscopy

Phase contrast microscopy Improved contrast,

allowing identification of structures in living cells

Allowed us to understand cell division

Won its inventor, Franz Zernike, the NOBEL PRIZE in 1951

Nobel Prize link to Phase microscope:

Phase Nobel

Contrast Microscopy Fluorescence contrast

techniques Immunofluorescence

techniques Here is a whole gallery of

beautiful images: Fluorescence Gallery Cell fluorescence

Electron Microscopy! Follows the same

principles as light microscopy, but shines a beam of electrons rather than light particles

The lower ‘wavelength’ of the electron beam allows incredible resolution

Can visualise particles to the order of a few angstom (10-10m)

Transmission Electron Microscopy

Wellcome scanning microscope

Designed by Ernst Ruska (Heidelberg) in 1938

He won the Nobel Prize just before his death, in 1986

First electron microscope was built in Toronto in 1938

Scanning Electron Microscope

Scanning Electron microscope

Scanning Tunneling Microscope

Sharing a Nobel Prize Scanning tunneling micr

oscopes