Microscopy

Maurice WetherallUniversity Senior College

“This material has been developed as a part of the Australian School Innovation in Science, Technology and Mathematics Project funded by the Australian Government Department of Education, Science and Training as a part of the Boosting Innovation in Science, Technology and Mathematics Teaching (BISTMT) Programme.”

Microscopy

Microscopes

• Our knowledge and understanding of the structure of cells has only been possible as a result of the use of microscopes.

• Light microscopes were first used in the 16th century.

• The electron microscope was developed in the 1930’s.

Anton Van Leeuwenhoek’s Simple Microscope - 1670

An English Tripod Microscope from around

1680

A 19th

CenturyMicroscope

A Current Compound

(Light) Microscope

Image From Light Microscope:

Onion Root Cells X1000

Compound Light Microscope

• Light from a light source is directed through the specimen.

• A combination of lenses is used to increase the resolving power of the human eye up to 500 times.

• Resolving power (or resolution) refers to the ability to distinguish fine detail.

• The magnifying power is calculated by multiplying the individual powers of the eye-piece (ocular) and objective lenses.

• e.g. 10x eye-piece, 40x objective = 400x

• Field diameter is the actual distance across the field of view.

• As magnifying power increases the field diameter decreases proportionally.

Compound Light Microscope

• The amount of light passing through the specimen can be adjusted using the iris diaphragm. This changes the contrast.

• The condenser lens is used to concentrate light on the specimen.

Compound Light Microscope

• The following is a short movie of a living amoeba magnified 1000X through a compound light microscope

• An amoeba is a microscopic unicellular animal that lives in water

• Note the cytoplasmic movement, and also the way the whole cell moves.

Amoeba X1000

Amoeba X1000

• This is a special type of light microscope, which provides greater contrast.

• Structures, which could not usually be seen without staining, show up.

• Staining cells kills the cells.• Phase contrast microscopes can be used to

observe living cells.• e.g. movement of chromosomes during

mitosis can be viewed.

Phase Contrast Microscope

• In an electron microscope, beams of electrons are focussed using magnetic lenses.

• The resolving power produced is up to 500,000 times greater than the human eye.

• Because a vacuum is needed, tissue has to be specially prepared, and so living cells cannot be examined.

Transmission Electron Microscope (TEM)

Transmission Electron Microscope (TEM)

Mitochondria

• The following slide shows mitochondria viewed through a transmission EM

• The internal structures of the mitochondria are visible. They are not visible through Light Microscopes.

Rough Endoplasmic Reticulum

• The following slide shows a section of rough endoplasmic reticulum.

• These flattened membranes are involved in synthesis and transport of proteins in cells.

• The small, dark dots are ribosomes.

Smooth Endoplasmic Reticulum

Electron Micrograph of Golgi Body

Scanning Electron Microscope

• An electron beam scans the surface of the specimen,

• Electrons are reflected off, and collected by a special electron detector.

• This provides an image, which appears on a computer screen and gives an impression of the outer shape of the specimen.

Scanning Electron Microscope at Adelaide Microscopy

• The following slide shows Year 11 students using one of the scanning EMs at Adelaide Microscopy.

Human Hair in a Scanning Electron

Microscope• The following specimens show human

hair, the first one is hair in good condition and is from a person using shampoo and conditioner that are free of Sodium Laurel Sulfate and Propylene Glycol

• The second is of poor quality hair from a person using shampoo and conditioner containing Sodium Laurel Sulfate and Propylene Glycol

The End