A2 - Microscopy

Magnification

Magnification

M = Image Size / Actual Size

Image Size

I = Actual size x magnification

Actual size

A = Image size / magnification

Scale bar

Indicates the certain length within the image

Light Microscope

You cannot see organelles of cells

No color

Uses light

up to x2000 magnification

Examine living organisms

Easy specimen preparation

200nm resolution
Inexpensive

Electron Microscope

You can see organelles

has no color

uses electron beams

up tp x500,000 magnification

Can’t examine living organisms

• because they will be killed by low frequency of beams

Complex specimen preperation

1nm resolution

Expensive

Sizes of things in a cell (Decreasing order)

Organelles

Bacteria (some are as large as organelles

Viruses

Membranes

Molecules

Benefits of Electron Microscopy

Shorter wavelength which increases magnification

2 Types of EM

SEM (scanning)

Beam of electrons to scan surface tension

You see the surface

No inner structure

TEM

Transmission

Aim beams of electrons through thin section of specimen

Goes through the cell, inner structure

Freeze Fracture

Technique employed for viewing of electron microscopy

Freezing biological specimen and then fracturing the specimen to look at 1 specific part

Cryogenic Electron Microscopy

Enable imag to be formed with computer enhancement that shows 3D framework of proteins functioning in cells

Techniques in light microscopy: fluorescent stains

Dyes that combine with specific cellular components that create ultraviolet or violet blue color that absorb the dye

Iminofluoresence

Allows greater visibility

Involves antibodies which already have dyes

Specific antibodies with unique color dyes are recognized and combined with target molecule

Often used to detect viral proteins in infected cells

µm

micro meter

100 micro meter is the smallest thing the human eye can see

1µm in nanometer

x 1000 = 1µm = 1,000nm

1mm to µm

x1000 = 1mm= 1,000µm