A2.2 Microscopy

resolution

The ability to form separate images of objects that are very close together

magnification

how much larger the object appears compared to its real size

Eyepiece graticule and stage micrometer

The graticule is lined up with the micrometer, the graticule stays the same size while the micrometer is magnified

electron microscope

-expensive

-can magnify up to 500,000x

-resolution of 0.1 nm

-requires cells to be killed and chemically treated before viewing

-black and white

Calculations involving Image size, Actual size, and Magnification

I AM

I/ AM

light microscope

-inexpensive

-easy to use

-used to study stained or living cells in color

-objects can be magnified 2000x

-can resolve objects 200nm apart

techniques used in microscopy

freeze fracture, cryogenic electron, immunofluorescence, fluorescent dyes

freeze fracture microscopy

involves freezing a sample and then using a specialised tool to break the sample into small pieces.

useful to observe structures that are not normally visible.

cryogenic electron microscopy

involves freezing a sample to

cryogenic temperatures (−180 °C or colder)

to fix the molecules, making them more firm or stable. The specimen is then viewed using electron microscopy.

higher resolution and lower damage from electron beam

Immunofluorescence

A technique in which a fluorescent molecule is attached to antibodies, which bind to antigens on a structure being viewed allowing visualisation of location of target molecules.

fluorescent dyes

Dyes that preferentially attach to certain structures and appear as brightly coloured spots.

structures viewed in both light and electron microscopes

membranes, mitochondria, chloroplast, flagella, vacuole, nucleus, cell wall

µm to nm

x 1000

mm to µm

x 1000

m to mm

x 1000