H L B I O L O G Y

C E L L S & B I O M O L E C U L E S

ELECTRON MICROSCOPY

LIMITATIONS OF THE LIGHT

MICROSCOPE

• Light microscopes rely on visible light being refracted to

magnify the image.

• Scientists were unable to study organelles without the

invention of a new, higher powered microscope.

Was invented in

the 1950s.

THE ELECTRON

MICROSCOPE

THE ELECTRON MICROSCOPE

• Rather than light, an electron microscope focuses a

beam of electrons onto or through the specimen.

• Modern electron microscopes are capable of obtaining

resolutions up to 100 times that of standard light

microscopes.

THE ELECTRON MICROSCOPE

• Electron microscopes come in 2 varieties:

• Scanning electron microscopes (SEM)

• Transmission electron microscopes (TEM)

Both are used in Biology for today, but for

different purposes.

SCANNING ELECTRON MICROSCOPES

• Are used to to study

the topography, or

outside surface of the

specimen. In an

SEM, the electron

beam scans the

surface of the

specimen

SEM image of a

midge (a small fly)

SCANNING

ELECTRON

MICROSCOPE

TRANSMISSION ELECTRON

MICROSCOPES (TEM)

• Are used to study the

internal structure of

cells

• TEM aim an electron

beam through a very

thin section of the

specimen, similar to

the way a light

microscope transmits

light through a slide.

TRANSMISSION ELECTRON

MICROSCOPES (TEM)

ROUGH ENDOPLASMIC RETICULUM

http://images.wellcome.ac.uk/

Rough Endoplasmic Reticulum

Smooth Endoplasmic Reticulum

Spot the

difference?

The ‘spots’ are the

difference!

The Rough

Endoplasmic Reticulum

is peppered with

ribosomes that give it

the rough appearance

It is where protein

synthesis occurs

GOLGI APPARATUS

PLANT CELL VACUOLE

MITOCHONDRIA

CHLOROPLASTS

What can you

see?