A2.2 Microscopy (1 of 4)

What does cell theory state?

All living things are made of one or more cells.

How did scientists decide on cell theory?

Through microscopy and inductive reasoning.

How much is a microscope magnifying?

The objective lens magnification multiplied by 10 (because the eyepiece magnifies 10X).

What is the formula for image size?

Actual size × magnification.

What is the formula for actual size?

Image size ÷ magnification.

What is the formula for magnification?

Image size ÷ actual size.

How many micrometers are in a millimeter?

1,000.

How many nanometers are in a millimeter?

1,000,000.

What are the limitations of a light microscope?

Relatively low resolution and magnification.

What is the definition of resolution?

Clarity of the image.

What are the drawbacks of electron microscopy?

Produces black-and-white images and samples are killed.

What do fluorescent stains do?

Absorb and re-emit light at a different wavelength.

What is immunofluorescence?

Uses various antibodies to bind to different structures so those structures appear in different colours.

How does freeze-fracture electron microscopy work?

Rapidly freeze a sample, fracture it with a steel blade, remove some ice, and add vapour to replicate the surface, creating a replica for study under an electron microscope.

What was freeze-fracture microscopy especially important for?

Understanding membrane structure.

What is Cryo-EM used for?

Studying protein structure.

How does Cryo-EM work?

A layer of proteins is frozen, then many images are imported into a computer that looks for patterns.

What units of matter can you see using Cryo-EM?

Atoms.

What is unique about Cryo-EM compared to other technologies?

Normal electron microscopy can only view proteins in their most stable form, while Cryo-EM allows proteins to be viewed in many different forms