Cell Structure Flashcards
2.1.1
What are the uses of stains?
- Coloured chemicals that bind to molecules in a specimen.
- Increases contrast: different components of the cell take up different amount of stains
- Details within the cell can be seen
What are examples of stains?
- Methylene blue: stains living cells blue
- Iodine solution : stains plant cells/ starch grains blue black
- acetic orein : staining nuclei and chromosomes red
- light green : stains plant and cell walls green
What is differential staining?
When you use one or more chemical stains . Different stains bind tp specfic structures>this can be used to show contrast between organelles, tissues and organelles
What is magnification?
Factor by which the image is larder than the actual specimen
What is resolution?
- The ability to distinguish between two separate point that are very close together
- More can be seen with a higher resoltion
- resoltion gives clarity
What is a laser scanning confocal mircosopes?
- A laser that scans specimen either on or below the surface which are usually tagged with fluoresent dyes and once scanned it gives of fluoresent light
- The light is focused through a pinhole
- Laser scannung microscopes can scan specimens at different depth
- Multiple images produces can be combined by a computer to produces a 3d Image
What are the advantages of a laser scanning confocal microscope?
- Can view live specimen
- high resolution + high contrast 3d image
- view cells as well
- focus on structures at different depths
What are the uses of a laser scanning confocal microscopes?
- Observe fungal filaments within the cornea of a patient with fungal corneal infection
- Used during endoscopy
What is a Scanning electron mircosope ?
- Coated in gold and dried
- The beam moves back and forth across the specimen. Electrons knocked off the specimen is detected which produces a image.
- 3d image
- Useful for the study of sufaces of objects
What is a transmission electron microscope ?
- Sample is thinned thinly
- Coated in hardened resin
- Passed through the specimen where some are obsorbed or passed through to the other side .
- Denser parts absord more electrons * 2d black and white image
- Internal structure of objects + cells
What is the maximum magnification and resolution of a SEM?
- Magnification: x200,000
- Resolution : 2nm
What is the maximum magnification and resolution of a TEM?
- Magnification: x2,000,000
- Resolution : 0.2nm
What is the maximum magnification and resolution of a Light microscope?
- Magnification: x2000
- Resolution : 200nm
Descrine how light mircoscopes work?
- Lenses focus rays of light and magnify the view of a thin slice of specimen
- Different structure absord different amount and wavelenths of light
- Reflected light is transmitted to the observer via the onjective lens and eyepiece
Describe how a TEM works
- Pass a high energy beam of electrons through a thin slice of specimen
- More dense structures appear darker since the absorb electrons
- Focus image onto fluoresent screen or photographic plate using magnetic lenses