2.1 - Cell Structure Flashcards
What is magnification?
It is how many times bigger an image is compares to its actual size
What is resolution?
It is the ability to differentiate between two points
What are the pros of a (optical)light microscope?
- Relatively cheap
- Easy to use
- Portable, can be used in the field
- Can study living specimen or dead specimen
- Clearly see some of the larger structures in cells
What are the cons of a (optical) light microscope?
- Low resolution so they are unable to look at small organelles clearly eg. Ribosomes
How does a light microscope produce an image?
It uses a glass lenses to focus the light to produce an image on the retina
How does an electron microscope work?
An electron beam is fired at a specimen and they are focussed by electromagnets, this happens in a vacuum.
Why is an electron microscope in a vacuum?
It is in a vacuum so that the electrons don’t collide with air particles.
What is used to stain specimen for an electron microscope?
Heavy metals like uranium or lead.
What is an electron microscope used to look at?
Small organelles and internal structures in dead specimen
What are the two types of electron microscopes?
-Transmission electron microscopes(TEM)
-Scanning electron microscopes(SEM)
What is the difference between a TEM and an SEM?
TEM:
-Electrons pass through the specimen
-Magnification is up to x500,000
-Resolution is up to 0.5nm
SEM:
-Electrons reflected off of the surface of the specimen
-Magnification is up to x100,000
-Resolution is between 3-10nm
What is a dry mount?
When the specimen is just covered by the cover slip
What is a wet mount?
When the specimen has water or a stain added to it before the cover slip is put on
What is a squash mount?
A wet mount that is the pushed down so there is only a thin layer for the light to pass through
What is a smear mount?
When the edge of another slide is used to smear the sample to create a thin and even layer, a cover slide is then added(usually blood).
What are an eyepiece graticule and a stage micrometer used for?
Calibrating a microscope
How do you calibrate a microscope?
1) Line up the stage micrometer and the eyepiece graticule whilst looking through the eyepiece
2) Count how many divisions on the eyepiece graticule fit into one division on the micrometer
3) This can be used to work out what one division on the eyepiece graticule is worth on the current magnification
What is the magnification calculation?
Size of image / Actual size
I.
A. M.
What are crystal violet and methylene blue?
Chemical stains that are positively charged, so are attracted to any negatively charged materials
What is gram staining?
-It is where you use crystal violet and saffron.
-Crystal violet turns gram positive bacteria blue/purple
-Saffron turns gram-negative bacteria red
Why is gram staining important?
It helps medics know what antibiotics to prescribe
What is a laser scanning microscope?
A microscope that uses a fine laser to illuminate the specimen
What is used to stain specimen for a laser microscope?
Fluorescent dye
What are the pros of laser scanning microscopes?
-High resolution
-Depth selectivity
-View sections of tiny structures
-Creates a 3D image
