Microscopy Flashcards
Explain why an electron microscope would be required to see the detailed structure of organelle Y.
- Needs a higher resolution;
- In order to distinguish between very close structures;
- Due to the shorter wavelength of electron beam.
An electron microscope has a much greater resolving power than an optical microscope.
Explain the meaning of the term resolving power.
The ability to distinguish from points (close together).
An electron microscope has a much greater resolving power than an optical microscope.
Explain the reasoning for this difference.
Electrons have a shorter wavelength than light.
Explain why it is possible to see the detailed structure of a prokaryotic cell with an electron microscope but not with a light microscope.
Electron microscope has a better resolution / able to distinguish between points more clearly;
Electron beam has a shorter wavelength.
Care must be taken in interpreting electron micrographs. Some features visible in an electron micrograph may not be present in the living cell, explain why?
Processes involved in the preparation may alter / distort the cell contents.
What is the magnification equation?
Magnification = Image size / Real object size.
What is the magnification?
How much bigger the image is than the specimen.
What is the resolution?
How detailed the image is, it is how well a microscope distinguishes between two close points.
If a microscope can’t separate two objects, what will further increasing the magnification do?
It will have no effect because the resolution stays the same.
If a microscope can’t separate two objects, what will further increasing the resolution do?
It will allow you to distinguish from closer points.
What are the two main type of microscope?
Optical (light) and Electron.
Which type of microscope uses light beams?
Optical microscopes.
Which type of microscope uses electron beams?
Electron microscopes.
Which type of microscope has a higher resolution?
Electron microscopes.
Why does the electron microscope have a higher resolution?
Because the wavelength of electrons are shorter than the wavelength of light.
Which type of microscope has a lower resolution?
Optical microscopes.
Which type of microscope gives a more detailed image?
Electron microscopes.
Which microscope is often used to look at organelles within cells?
Electron microscopes.
Which microscope has a resolution of about 0.2 micrometers (um)?
Optical microscope.
Which microscope has a resolution of about 0.0002 micrometers (um)?
Electron microscope.
What is the resolution of an electron microscope?
0.0002 micrometers (um).
What is the resolution of an optical microscope?
0.2 micrometers (um).
Which microscopes can you see the nucleus through?
Both optical and electron.
How much greater is the maximum resolution of an electron microscope than an optical microscope.
1000x higher, 0.0002um instead of 0.2um.
What is the maximum useful magnification of an optical microscope?
x1,500.
What is the maximum useful magnification of an electron microscope?
x1,500,000.
Compare the maximum useful magnification of an optical microscope and an electron microscope.
Optical = x1,500. Electron = x1,500,000.
What are the two types of Electron Microscope?
Transmission electron microscope (TEMs) and Scanning electron microscope (SEMs).
Which type of microscope uses electromagnets to focus a beam of electrons?
Transmission electron microscopes (TEMs).
In TEMs, what happens to the focused beam of electrons?
It is passed through the specimen.
In TEMs, how is the electron beam focused?
Through the use of electromagnets.
In TEMs, what makes the specimen appear different colours?
Dense parts of the specimen absorb more electrons making them look darker.
Which type of microscope can only be used with thin specimens?
Transmission electron microscopes (TEMs).
Which type of electron microscope has a higher resolution?
TEMs have a higher resolution than SEMs.
What are the advantages of TEMs?
High resolution so you can see the internal structure of organelles like chloroplasts.
What are the disadvantages of TEMs?
Thin specimens.
What are the advantages of SEMs?
Can be used on thick specimens.
What are the disadvantages of SEMs?
Lower resolution than TEMs.
Which type of microscope should be used on a thick specimen?
Scanning electron microscope (SEM).
How do SEMs work?
They scan a beam of electrons across the specimen, knocking off electrons from the specimen, gathered in a cathode ray tube to form an image.
Which microscope used a cathode ray tube?
Scanning electron miscroscope (SEM).
Which microscope creates a 3-D image?
Scanning electron microscope (SEMs) produce 3-D images of the surface of a specimen.
How do you prepare a ‘temporary mount’ of a specimen on a slide?
- Pipetting a small drop of water onto the slide.
- Add a drop of stain.
- Add a cover slip making sure there are no air bubbles.
What are slides? (In an optical microscope)
Strips of clear glass or plastic.
What are stains used for? (In an optical microscope)
They are used to highlight objects in a cell.
What is the function of an eosin stain? (In an optical microscope)
To make the cytoplasm show up.
What is the function of an iodine stain? (In an optical microscope)
To stain starch grains in plant cells.
What is the function of the eyepiece? (In an optical microscope)
You look down it.
What is the function of the coarse adjustment knob? (In an optical microscope)
To bring the specimen roughly into focus.
What is the function of the fine adjustment knob? (In an optical microscope)
To finely tune the focus.
What is the function of the stage? (In an optical microscope)
Where the microscope slide is placed.
What is the function of the light? (In an optical microscope)
To allow you to see through the specimen.
What are the high and low power objective lenses? (In an optical microscope)
They are used to magnify the objective.
The detailed ultrastructure of cells was revealed in the 1950’s, what caused this discovery?
The introduction of electron microscopes.
What is the name for the image created by the electron microscopes?
Electron micrographs.
What does a microscope do?
Produce a magnified image of an object or specimen.
Who created the first microscope powerful enough to explore microbes?
Anton van Leeuwenhoek (1632-1723).
How does a compound light microscope work?
Light passes through the specimen and then through two sets of glass lenses, the objective lens and ocular or eyepiece lens, they refract the light to give a magnified image of the object.
If the image in an optical microscope is projected onto a photographic film, what is the name given to the result?
A photomicrograph or a light micrograph.
What is a photomicrograph?
A photograph taken inside an optical microscope.
What is resolving power?
The limit of effective magnification, where a microscope can show two objects as seperate.
Which microscopes can be used to see mitochondrion?
Light and Electron microscopes.
Which microscopes can be used to see a virus?
Electron microscopes.
Which microscopes can be used to see plant and animal cells?
Light and Electron microscopes.
Which microscopes can be used to see ribosomes?
Electron microscopes.
Which microscopes can be used to see protein molecules?
Electron microscopes.
Which microscopes can be used to see lipid microscopes?
Electron microscopes.
Which microscopes can be used to see most bacterium?
Light and Electron microscopes.
Compare the wavelengths of light beams and electron beams?
Electron beams have much shorter wavelengths.
Which type of microscope would you use for performing a count of white blood cells from the blood of a person with an infection?
Compound light microscope.
Which type of microscope would you use for resolving the ultrastructure of a chloroplast?
Transmission electron microscope (TEM).
Which type of microscope would you use for distinguishing extinct plant species on the basis of pollen surface features?
Scanning electron microscope (SEM).
Which type of microscope would you use for counting the heart rate and rate of limb beating in a water flea?
Dissecting microscope.
Which microscopes can be used for living specimens?
Compound light microscopes.
How is the specimen prepared for a SEM microscope?
It must be non-living and supported on a metal disc in a vacuum.
How is the specimen prepared for a TEM microscope?
It must be non-living and supported on a small copper grid in a vacuum.
How is the specimen prepared for a light microscope?
It can be living or dead, supported on a glass slide.
Which has a higher maximal resolution, TEM or SEM?
TEM.
What stains are used in an optical microscope?
Coloured dye, a surface or section.
What stains are used in a transmission electron microscope?
impregnated with heavy metals.
What stains are used in a scanning electron microscope?
Coated with carbon or gold.
The book micrographia contained details of the first compound microscope, who created this?
Robert Hooke (1660’s).
What are the cost differences between an optical microscope and an electron microscope?
Optical is low cost and electron is high cost.
