Microscopes
- Created by: Simranlouise
- Created on: 19-11-17 20:40
View mindmap
- Microscopes
- Use for cell structure
- Electron Microscope
- 1. Uses electrons to form an image.
- 2. Has a higher resolution than optical microscopes to give a more detailed image (and can be used to view all organelles).
- 3. Maximum resolution of about 0.0002 micrometres (?m) - about 1000 times higher than optical.
- 4. Maximum useful magnification of an electron microscope is about x 1,500,000.
- 3. Maximum resolution of about 0.0002 micrometres (?m) - about 1000 times higher than optical.
- 2. Has a higher resolution than optical microscopes to give a more detailed image (and can be used to view all organelles).
- 1. Uses electrons to form an image.
- Optical (light) Microscope
- 1. Uses a light to form the image
- 2. Has a maximum resolution of about 0.2 micrometres (?m).
- You cannot view organelles that are smaller than 0.2?m
- Including ribosomes, the endoplasmic reticulum and lysosomes.
- Mitochondria may be visible but not clear. You can see the nucleus.
- Including ribosomes, the endoplasmic reticulum and lysosomes.
- 3. Maximum useful magnification of optical microscopes is about x1500.
- You cannot view organelles that are smaller than 0.2?m
- 2. Has a maximum resolution of about 0.2 micrometres (?m).
- 1. Uses a light to form the image
- Electron Microscope
- Basic Microscopes
- Transmission Electron Microscope (TEM)
- 1. Uses an electromagnet to focus a beam of electrons, which is transmitted through a
specimen.
- 2. The densest parts of the specimen absorb more electrons, which makes them look darker.
- 3. TEMs produce a high resolution image to see internal structure of organelles.
- 4. They can only be used on thin specimens.
- 3. TEMs produce a high resolution image to see internal structure of organelles.
- 2. The densest parts of the specimen absorb more electrons, which makes them look darker.
- 1. Uses an electromagnet to focus a beam of electrons, which is transmitted through a
specimen.
- Scanning Electron Microscope (SEM)
- 1. Scans a
beam of electrons over the specimen that knocks off electrons that are gathered
in a cathode ray tube to form an image.
- 2. The images
show the surface of the specimen and can be 3D.
- 3. Good for use on thick specimens.
- 4. SEMs give a lower resolution image than TEMs.
- 3. Good for use on thick specimens.
- 2. The images
show the surface of the specimen and can be 3D.
- 1. Scans a
beam of electrons over the specimen that knocks off electrons that are gathered
in a cathode ray tube to form an image.
- Transmission Electron Microscope (TEM)
- Temporary slide mounting
- 1. Pipette a
drop of water onto the slide and use tweezers to place a thin section of the specimen
on the drop.
- 2. Add a drop of stain to highlight objects in the cell (e.g. eosin for cytoplasm, iodine in potassium iodine solution for starch grains in plant cells).
- 1. Pipette a
drop of water onto the slide and use tweezers to place a thin section of the specimen
on the drop.
- Fixing Samples
- 1.
Heat-fixation by using a slide warmer.
- 2. Heat-fixation by holding a specimen a slide with a smear over a micro incinerator.
- 3. Chemical fixation by using chemical agents like acetic acid, ethanol, methanol and formaldehyde (formalin), which denature proteins, stop biochemical reactions, and stabilise cell structures in tissue samples.
- 2. Heat-fixation by holding a specimen a slide with a smear over a micro incinerator.
- 1.
Heat-fixation by using a slide warmer.
- Magnification
- Magnification is how much bigger the image appears than the specimen sample is. It’s calculated using this formula: magnification = size of image/ size of real object
- If no scale bar is given, use the formula actual size = image ÷ size magnification.
- If you are given the size of the image and the size of the sample in different units in your exam you will need to convert them into the same units before using the formula.
- You also need to be able to rearrange the formula and look for the units required in the answer.
- Resolution
- The resolution is how detailed the image is. The better the resolution, the better the microscope is able to distinguish between two points that are close together. If a microscope cannot separate two objects, more magnification will not help to see them.
- Outputs of a microscope
- Light microscopy as well as electron microscopy produce images, which can be deciphered to the construction of the cellular level. Images produced by each of these vary and can be used as needed.
- Use for cell structure
Comments
No comments have yet been made