Studying Cells Flashcards
(25 cards)
What can be seen using a TEM?
Small objects
What is the resolution of a TEM?
TEM has high resolution
Why does TEM have high resolution?
Electron wavelength is shorter
Can living cells be observed with a TEM?
No, cannot look at living cells
How must specimens be cut for TEM?
Must cut section / thin specimen
Where are samples placed in TEM?
Must be in a vacuum
What is a limitation of specimen preparation for TEM?
Preparation may create artefact
Why is resolution higher in an electron microscope than in an optical microscope?
Shorter wavelength between electrons
What causes lower resolution in optical microscopes?
Longer wavelength in light (rays)
What is one advantage of TEM over SEM?
Higher resolution
What is another advantage of TEM over SEM?
Higher (maximum) magnification / higher detail (of image)
What internal details can TEM show that SEM cannot?
Allows internal details / structures within (cells) to be seen / cross section to be taken
What is one advantage of SEM over TEM?
Thin sections do not need to be prepared
What can SEM show that TEM cannot?
Shows surface of specimen / can have 3-D images
Why use an isotonic solution when isolating mitochondria?
Prevents osmosis / no (net) movement of water So organelle/named organelle does not burst/shrivel
Why use ice-cold conditions during mitochondria isolation?
Reduce/prevent enzyme activity so organelles are not digested / damaged
Why use a buffered solution when isolating mitochondria?
Maintain a constant pH so proteins do not denature
What is cell homogenisation used for?
To break open cells and release organelles
What is the purpose of filtering during cell fractionation?
Filter to remove (large) debris/whole cells
Why use isotonic solution during fractionation?
To prevent osmotic damage to mitochondria / organelles
Why keep samples cold during fractionation?
To prevent/reduce damage to organelles by enzyme
Why use a buffer during fractionation?
To maintain pH and prevent protein/enzyme denaturation
What does the first differential centrifuge at 1000 g separate?
Nuclei / cell fragments / heavy organelles
What is done to the supernatant after nuclei/pellet is removed?
Re-spin at higher speed to get mitochondria in pellet/at bottom
