3.1) Methods of Studying Cells Flashcards
What is magnification?
How many times bigger an image appears compared to the actual size of the object being observed
What is magnification?
How many times bigger an image appears compared to the actual size of the object being observed
What is the magnification equation?
magnification= image size/ real size
What is resolution?
The ability to distinguish two different points in a specimen.
What is a light microscope’s resolution limit?
0.2 micrometers
Which microscope has the higher resolution: The light microscope or the electron microscope?
The electron microscope
Why do electron microscopes have a higher resolution?
Because of the shorter wavelength which allows them to distinguish between objects as close as 0.1 micrometers
What happens if we increase the magnification beyond the limit of resolution?
It doesn’t provide clearer images but makes the image larger and more blurry
What is cell fractionation?
The process by which cells are broken up and different organelles are separated out
What does steps must take place before cell fractionation can occur?
The tissue is cut up and kept in cold, buffered solution at the same water potential as the tissue.
Why is the solution before cell fractionation can occur kept cold?
To reduce enzyme activity that might break down organelles.
Why is the solution before cell fractionation kept at the same water potential as the tissue?
To prevent organelles from bursting or shrinking
Why is the solution before cell fractionation can occur buffered?
To ensure the pH doesn’t fluctuate
What could the fluctuation of pH affect in cell fractionation?
It could change the structure of organelles or affect the functioning of enzymes
What are the two stages to cell fractionation?
- Homogenisation
- Ultracentrifugation
What is meant by homogenisation?
The process by which cells are broken up by a homogeniser (blender), which releases organelles from the cell.
What is meant by the term homogenate?
It is the resultant fluid which is filtered to remove any complete cells or large pieces of debris.
What is meant by ultracentrifugation?
The process by which the fragments in the filtered homgenate are seperated in a centrifuge.
What is meant by the term centrifuge?
A machine that spins the tubes of homogenate at very high speeds in order to create a centrifugal force
What does steps take place in the process of ultracentriguation?
- The tube of filtrate is placed in the centrifuge and spun at a slow speed
- The heaviest organelles (nuclei) are forced at the bottom of the tube where they form a thin sediment or pellet
- The fluid at the top of the tube (supernatant) is removed, leaving just the sediment of nuclei.
- The supernatant is transferred to another tube and spun in the centrifuge at a faster speed than before
- The next heaviest organelles (mitochondria) are forced at the bottom
- The process is continued this way , so that at each increase in speed, the next heaviest organelle is sedimented and separated out
What is the order of the organelles that will be sedimented and separated out during the process of ultracentrifugation?
- Nuclei
- Mitochondria
- Lysosomes
What is the speed of centrifugation for nuceli?
1,000 revolutions min ^-1
What is the speed of centrifugation for mitochondria?
3,500 revolutions min ^-1
What is the speed of centrifugation for lysosomes?
16,500 revolutions min ^-1
