Unit 2 Cells Microscopy Flashcards
How does the radiation travel in a Transmission Electron microscope?
The radiation pass throught the sample then into the objective lenses.
How does the radiation travel in a Scanning Electron microscope?
The radiation passes through the sample then into the objective lenses.
What is the radiation source in the electron microscope?
The radiation source is an electron beam.
What is the radiation source in the light microscope?
The radiation source is light
If there is higher resolution then what is the knock on effect?
Higher magnification
If there is higher magnification then what happens to the image?
The image appears to be larger
What instrument does the TEM use to detect the electrons?
Fluorescent screens
What instrument does the SEM use to detect the electrons?
Computer programme
What can help to focus the electron beam in a TEM?
Electromagnets
What can help to focus the electron beam in a light microscope?
Glass lenses
What is used to detect the light emitted by the light microscope?
The eyes
What is the definition of resolution?
Resolution is the smallest distance between two separate objects that can be distinguished
What is the difference in wavelengths between light and electrons?
Light has a larger wavelength whereas electrons have a smaller wavelength
How do the samples have to be when the light microscopes are used?
They can be either dead or alive
How do the samples have to be when the electron microscopes are used?
They have to be dead
What is the area around the sample must be within an electron microscope called?
The vacuum
If a sample within an electron microscope not surrounded by a vacuum what happens?
When the electron beam is fired from the electron gun it hits the air particles around which can ionise the particles so it produces random spurs of images.
What is the formula for magnification?
Magnification = Image size / Actual Size
How many mm in a cm?
10
How many mm in a metre?
1000
How many micrometres in a mm?
1000
How many nanometres in a micrometre?
1000
What is the standard form formula for 1 nm?
1 x 10^-9
What is the standard form formula for 1 micrometre?
1 x 10^-6
What is the maximum resolution for a light microscope?
0.2 micrometres apart
What is the maximum resolution of electron microscopes?
0.1 nanometres apart
What is the maximum magnification for light microscopes?
2000x
What is the maximum magnification for electron microscopes?
Over 500,000x
What are the limitations for electron microscopes?
Expensive, stored at specific temp and difficult to use
What are the pros of electron microscopes?
Have high magnifications and higher resolutions so give more detail
What are the limitations of light microscopes?
Have low resolution and low magnification so less detail than the electron microscopes
What are the pros of light microscopes?
Easy to use, cheap and don’t require a specific temp to be stored in
What is the formula for calculating the magnification of an object?
Magnification = image size / actual size
What is cell fractionation?
Cells are broken up and different organelles within the cell are separated out
What are 3 things that a solution must be like in order to undergo cell fractionation?
Cold isotonic and be a buffered solution
Why is a cell put in a cold area?
To reduce enyme activity that might break down organelles.
Why is a cell put in an isotonic surrounding?
To prevent the organelles from shrinking or becoming swollen as a result of osmotic gain or loss
Why is a cell placed in a buffered solution?
So that the pH doesn’t fluctuate this could lead to enzyme activity being decreased due to denaturation
What are the 2 stages of cell fractionation?
Homogenation and ultracentrifugation
How does homogentaion work?
Homogentaion is when the cells are broken by a homogeniser releasing the organelles.
What are the products of homogenation?
The homogenate - resultant fluid
The pallet - large pieces of debris and cell
What happens to the homogenate after homogenation?
The homogenate is filtered so that it removes any large pieces of debris or any unbroken cells
What is the process of Ultracentrifugation?
Fragments in the filtered homogenate are separated in a machine called the centrifuge
What does the centrifuge do?
The centrifuge spins tubes of the homogenate at very high speeds in order to create a centripetal force.
What happens to the components of the cells within the homogenate after ultracentrifugation?
The heaviest organelles such as the nuclei are the densest and so lay at the bottom of the tube forming a pellet.
The rest of the organelles are less dense and so they form the fluid called the supernatant
What happens to the supernatant after ultracentrifugation?
It is filtered and then put into another tube and spun at even faster speeds than before
What are the top 3 heaviest organelles within the human cell?
Nucleus then mitochindria then lysosymes
What is the heaviest organelle after the nucleus in the plant cell?
Chloroplast
What is a photomicrograph?
An image produced on the screen and then photographed
Using a light microscope how is the size of the objects measured?
Using a eyepiece granule
How is the eyepiece graticule calibrated? Using what instrument?
Using a stage micrometer
What is the lowest magnification on light microscope?
x4
What is the total magnification ?
eyepiece lens x objective lens
How is the eyepiece graticule calibrated?
The EPG and the stage micrometer scale are aligned
