🩶 3.2.1.3 Methods Of Studying Cells Flashcards
(21 cards)
What is the magnification equation?
Magnification = size of image / size of real object
How to get from cm to micrometer ?
Times 10000
How to get from micrometer to cm ?
Divide by 10000
Define magnification
How much bigger the image is than the actual object
Define resolution
The ability to distinguish between two points and it shows the detail of an object
What are the two types of microscopes?
Light (compound) and electron microscopes
How many types of electron microscopes are there and what are they?
There are two types of electro microscopes they are TEM and SEM
What does TEM stand for?
Transmission electron microscope
What does SEM stand for?
Scanning electron microscope
Compare the light and electron microscope to each other.
- light microscope has a lower magnification than an electron microscope
- light microscope has a lower resolution (longer wavelengths of light so resolution is lower) than an electron microscope
- light microscope is cheaper than an electron microscope
- light microscope is smaller than an electron microscope
- light microscope is transportable whereas an electron microscope isn’t
- you can study living things under a light microscope but not under an electron microscope (due to a vacuum which living specimen cannot survive under)
- the images produced by light microscopes are coloured however under electron microscopes they are black and white and require colour to be added to the image
- there are fewer artefacts under light microscopes so less complex to prepare than electron microscopes
Define an artefact
Artefact is something that shouldn’t be under the microscope for example dust
How do TEM microscopes work?
Electrons are accelerated towards the positive anode and are focused on it by electromagnets. The denser area of the specimen absorbs more electrons and therefore appears darker on the screen.
How do SEM microscopes work?
Similar to the TEM, the SEM electrons accelerate through an anode and are focused by electromagnets onto the specimen. The electrons are then deflected of the specimen, and are detected, and then form the image on a screen.
Compare an SEM and TEM magnification and resolution
In an SEM resolution and magnification are higher than light microscopes but lower than TEM
What kind of image is produced by an SEM and how is this done?
SEM produce a 3-D image by scanning the surface of the specimen
What kind of images is produced by a TEM and how is this done?
They scan the inside of a specimen and produce a 2-D image
What is cell fractionation?
The process of separating cell organelles from each other
During homogenisation what are the three properties of the solution that the tissue is initially placed in?
1) ice cold - to prevent enzymes hydrolysing the organelles
2) isotonic - to stop water entering or leaving, by osmosis causing the organelles to shrivel or burst
3) pH buffer - to prevent proteins from becoming denatured
What happens after the tissue is taken out of the solution?
The tissue is blended into a homogenous in order for the cell membrane to break and the organelles to be released from the cell into the homogenate solution (this happens after it’s been taken out of the solution)
What happens during filtration ?
The homogenate is filtered to remove debris e.g whole cells
What happens during ultracentrifugation ?
1) The solution is the input into a centrifuge tube and then into a centrifuge which spins round at its slowest speed.
2) After spinning, there is a pallet at the bottom of the tube with the super Natan above it. The pellet contains the densest organelles.
3) the super Natan is decanted into a second tube and then spun again. This time though faster and for a long time.
4) the pellet will now contain the second densest organelle
5) this process is repeated until the desired organelle is obtained
