1. Measurement & Microscopes

2. Sizes of Things
Size relative
Prefix Meaning to a meter Length
Kilo- thousand kilometer (km)
Centi- hundredth centimeter (cm)
Milli- thousandth millimeter (mm)
Micro- millionth micrometer (µm)
Nano- billionth nanometer (nm)
4 mm
2 mm
200 µm
With the unaided eye, you can see down to about 200 µm (that’s 0.2 mm).
With a quality light microscope, you can see something as small as 200 nm clearly (that’s mm).
With an electron microscope, you can visualize something as small as 0.2 nm clearly (that’s mm or otherwise stated, 2x10-7 mm).
200 nm
Check out:

3. Sizes of Things & Photomicrography
Check out:
How Big?
Scale of the Universe
Olympus Bioscapes Competition winners
Nikon Small World Competition (photo & video)

4. Microscopes: Tools of Biologists
Different microscopes have different advantages and disadvantages. Biologists use different microscopes depending upon what they want to look at / observe.
________________________: also called a stereo microscope
2 eyepieces
2 lenses, __________ and ___________ (in the eyepiece)
2 lamps, one above and one below the specimen
Advantages:
Specimen can be alive
No special preparation of specimen needed
Easy to use!
Relatively inexpensive
Disadvantages:
Low magnifying power (up to 60x usually)
Dissecting
Microscope
objective
ocular lens

5. Compound Light Microscope ______________________________
2 lenses, __________ and ___________ (aka eyepiece)
On student ‘scope, usually have 10x ocular lens & several objective lenses: 2x (scanning), 10x (low power), & 40x (high power)
Sample often placed in _______ on a slide
Some specimens are stained or “fixed” with dyes -- this enhances contrast & helps preserve specimen (but kills it too)
Light passes _________ sample and is “bent” by lenses to produce a magnified image
Advantages:
Specimen can be alive
Easy specimen preparation
Relatively easy to use
Fairly inexpensive for a basic ‘scope
Can magnify up to _______ clearly
Disadvantages:
Cannot see anything smaller than ______________
(note: a small cell is about 10 µm across)
objective
ocular lens
water
through
1000x
0.2 µm (200 nm)

6. Modern Optical Microscopes with Digital Camera attachments

7. Transmission Electron Microscopy

8. TEM Specimen Preparation
In TEM, the specimen must be thin enough to allow electrons to travel through the tissue.
You can cut very thin slices of your specimen either by fixing it in plastic or freezing it. The specimen is cut into thin sections by a diamond knife in an instrument called ultramicrotome. Each section is only nm thick. A thin section of your sample is placed on a copper grid and stained with a heavy metal, like uranium & lead, which scatters electrons well and improves the contrast in the microscope. The slice of tissue can now be studied under the electron beam.
Alternately, a solution of isolated material (can be a solution with bacteria or a solution with isolated molecules) is spread on a support grid coated with plastic. A solution of heavy metal salt is added. The metal salt solution does not bind to the material but forms a "shadow" around it on the grid. The specimen will appear as a negative picture when viewing it in the TEM.
An ultra-microtome slices samples as fine as 70 nm thin so they can be viewed in a transmission EM.

9. Scanning Electron Microscopy

10. • Electron Microscopes
Sends beam of _________ over or through specimen
This beam is bent by large _______________ to produce a magnified image
There are two main types of electron microscopes:
_____________ Electron Microscope (TEM)
Beam of electrons passes ________ an ultra-thin section of a specimen and onto a fluorescent screen or photographic film
Images produced are ________________ of specimens
__________ Electron Microscope (SEM)
Beam of electrons passes over the _______of a specimen, electrons bounce off at different angles & are “read” to produce image
Images are ____ pictures of the ________ of samples (no inside views)
electrons
electromagnets
Transmission
through
cross-sections
Scanning
surface 3D
surface

11. TEM ____ Micrographs Pancreatic cell Golgi body Herpes virus
Bacillus subtilis bacterium
Herpes virus
Nucleus surrounded by rER
Mitochondria (in lung cells)

12. ____ Micrographs SEM Hair shaft Can you guess what this is?
____ Micrographs
SEM
Hair shaft
Can you guess what this is?
Ebola Viruses (one w/ false color)
The fossilized shell of a microscopic ocean animal, magnified 392 times its actual size. The ancient creature, called Radiolarian, lived in the waters off Antarctica and is now used to study such things as climate and ocean circulation.

13. What is this?

14. White blood cell (B-cell) with viruses budding out of it.

15. TEM (above) and SEM (below) of viruses budding from a mammalian cell

16. • Electron Microscopes
Advantages:
Can be used to view smaller things like ________ and _____________________ that cannot be seen with light ‘scopes
Can magnify over 100,000x and allows you to see objects as small as _______
Disadvantages:
Preparation of specimen can be _________
Ex)
Cannot view living organisms
Much more complex & difficult to use/operate than light ‘scope
Extremely expensive to buy and maintain
Only produces ______________ images (any color electron micrographs have false color added afterwards by computer)
viruses
sub-cellular organelles
0.2 nm
difficult
Freezing or embedding in resin, slicing ultra-thin sections
black & white

17. Virtual Electron Microscopy