A2.2 Microscopy

Cell theory

all living things are made of one or more cells

I AM

Image over actual and magnification

Microscopy units

In microscopy, common units for measuring small distances include millimeters (mm), micrometers (µm), and nanometers (nm). These units are used to measure the size of objects and structures viewed through a microscope. 

Here's a breakdown of the units and how they relate to each other:

• Millimeter (mm): 1 meter (m) = 1000 millimeters. 

• Micrometer (µm): 1 millimeter (mm) = 1000 micrometers. 1 micrometer is also one millionth of a meter. 

• Nanometer (nm): 1 micrometer (µm) = 1000 nanometers. 

Conversions:

• mm to µm: Multiply by 1000.

• µm to nm: Multiply by 1000.

• mm to nm: Multiply by 1,000,000 (or 10^6). 

Example:

8.5 mm = 8,500 µm = 8,500,000 nm. 

Light microscopes

limitations of magnification and resolution

Electron microscopes

use electrons instead of light, has a better magnification and resolution

drawbacks: Black and white, kills the cells

Fluorescent stains

absorb and then re-emit light at a different wavelength (brightening)

Immunofluorescence

uses antibodies to bind to different structures. Different fluorescent stains bind to different antibodies, creating different colored images

Freeze-fracture electron microscopy

Freeze-fracture electron microscopy (FFEM) is a technique used to study the internal structure of biological membranes by rapidly freezing a sample, fracturing it at a low temperature, and then creating a replica of the fractured surface for viewing under a transmission electron microscope. This allows researchers to examine the arrangement of proteins and lipids within the membrane bilayer. 

Cryogenic electron microscopy (cryo-EM)

Cryogenic electron microscopy (cryo-EM) is a powerful technique that allows researchers to visualize biological molecules in their near-native state at near-atomic resolution. It involves rapidly freezing biological samples in vitrified ice, then using an electron beam to image them at extremely low temperatures. This technique is crucial for understanding the structure and function of proteins, viruses, and other biomolecules