Microscopes Flashcards
What is magnification?
How many times bigger the image is compared to the object
What is resolution?
The minimum distance apart that 2 objects can be in order for them to appear as separate items
What units are cells and cell organelles usually measured in?
μm (micrometres)
what are the conversions from micrometres to millimetres?
1mm = 1000μm
multiply the millimetres by 1000 to get to micrometres
What is the formula for total magnification?
eyepiece lens magnification x optical lens magnification
What are the equations for image size, actual size and magnification?
image size = actual size x magnification
actual size = image size/magnification
magnification = image size/actual size
What is the equation for actual size using a scale bar?
Actual size = (image length/scale bar length) x scale bar value
What is the equation for magnification using a scale bar?
Scale bar length x 1000
What does cell fractionation and ultracentrifugation allow us to do?
Study the structure and function of organelles
What is cell fractionation?
The breaking up of cells
What is ultracentrifugation?
Separating organelles
What is the process of cell fractionation?
· The cells are homogenised (broken up) by either a pestle and mortar, a blender or a homogeniser
· The fluid mixture left is called the homogenate
· The homogenate is suspended in a buffer solution
· The homogenate is filtered to remove bits of cells that have not been broken up fully
What is the process of ultracentrifugation?
- Homogenate is put in the centrifuge and span at the lowest speed
- The largest organelles are separated first and form a pellet at the bottom of the tube
- If other organelles are wanted, the liquid on top of the pellet (supernatant) can be spun at a higher speed
What are the requirements that a specimen has to be to see it in a light microscope?
- Must be cut thinly
- A stain may have to be used
What are pros and cons of a light microscope?
+ Cheaper than an electron microscope
+ Can see in colour
+ Specimens can be living or dead
- Wavelength of light limits the resolution
- Magnification is not as good as in an electron microscope
How does an electron microscope broadly work?
A beam of electrons are passed through a specimen
Focused by electromagnets onto a fluorescent screen to produce an image
What are the two types of electron microscope?
Scanning Electron Microscope (SEM)
Transmission Electron Microscope (TEM)
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