Microscopes Flashcards
Which microscopes can be used on living samples and a color image is obtained
Light micrscopes
What is a dry mount sample preparation
This is when thin dry slices or whole dry specimens are viewed with just the coverslip placed on top e.g hair or plant tissue
- What is a wet mount sample preparation
- What specific type of animal can be viewed this way
- This is when water or a stain is added to the specimen before lowering the coverslip with a needle to prevent air bubbles
- Aqauatic amimals
What’s a squashed slide
squash slides are wet mounts which have had the coverslip squasheed down on it to ensure the sample is thin enough for light to pass through
What are smear slides used for
There are used when examining blood cells in a blood sample
What is differential staining
differential staining is a technique which involves many chemical stains being used to stain different parts of a cell in different colors
- Which 2 stains are positively charged
- What do they do
- Crystal violet’and methylene blue
- These are attracted to and stain negatively charged material
- Which two stains are negatively charged
- What do they do
- Nigrosin and Congo red
- These cannot enter the cells as cytosine repels them therefore they create a stained background and the unstained cells then stand out
What are the four types of cell preparation
- Dry mount
- Wet mount
- Smear slide
- Squash slide
What’s a slide
Thin flat piece of glass used to hold objects for examination under a microscope (75 by 26mm)
What’s a stain
Colored chemicals that bind to molecules on or in a specimen
Gram stainingis a type of differential stain where you use two different stains
1. to identify what
2. What are the two stains
- To identify what type of bacteria is present
- Crystal violet and safranin
What is the process of adding crystal violet to the stains
- Add crystal violet
- Add iodine to fix the stain
- Alcohol added to wash any unbound stain to avoid it all looking dark
- What color do gram positive bacteria appear
- Why
- Blue/purple
- The stain is retained due to the thicker peptidoglycan cell wall absorbing the dye
- Why can’t gram negative bacteria absorb crystal violet
- What is added instead
- What color does this turn the bacteria
- Peptidoglycan cell wall is thin so they don’t retain the stain due to the thinner wall
- Safranin is used as a countertstain
- Red
1.Why must electron microscope be used in a vacuum/only dead specimen
- Electrons are absorbed by air therefore only non living specimen can be examined
Why do electron microscopes have a high wavelength
A beam of electrons have a very short wavelength therefore a high resolution
What color is the imagine produced in an em microscope and why
Black and white as the sample must be stained
Which type of electron microscope needs thin specimen and why
Transmission electron microscopes need an extremely thin specimen as the electron gun passes a beam of electrons through the specimen whereas in scanning electron microscopes the electrons are beamed onto the surface and scattered in different ways depending on the contours
- What type of microscope is the laser scanning microscope
- Fluorescent microscope
1.what type of image do laser scanning microscopes produce
2.Is the image high or low resolution
1.3D and 2D
2.high resolution
whats another word for confocal microscopes
laser scanning microscopes
WHATS A STAIN
stains are colored chemicals that bind to molecules in or on the specimen which makes it easier to see
1.what does acetic orcein bind to
2.what color does it stain chromosome
1.DNA
2.red
