Microscope Flashcards
How to measure objects using an eyepiece graticule
Use eyepiece graticule to measure the object.
Calibrate eyepieces graticule against stage micrometer .
Take a number of measurements and calculate the mean
Advantages and limitations of transmission electron microscope
Adv:small objects can be seen.
TEM has high resolution as wavelength of electrons shorter
Limitation : cannot look at living cells as cells must be vacuum .
Must be thin specimen.
Dos not produce colour image .
Comparison of TEM and optical microscope
TEM use electrons and optical use light .
TEM allows greater resolution
With TEM smaller organelles can be observed.
TEM view only dead specimens and optical can view live specimens .
TEM does not show colour and optical can.
TEM require thinner specimens .
TEM requires a more complex preparation.
TEM focuses using magnets and optical uses glass lenses
Advantage of electron microscope over optical microscope
High resolution.
Can see internal structure of organelles
The resolution of an image obtain using an electron microscope is higher than resolution of an image obtain using optical microscope explain why
Shorter wavelength between electrons .
Describe and explain one difference between TEM and SEM
3D image with SEM
Lower resolution with SEM
Only surface visible with SEM , internal structure visible with TEM ,because electrons deflected using SEM .
Condition require foe cell homogenisation
Ice cold -stop enzymes activity to prevent digestion of organelles .
Buffered- maintain pH so that enzymes are not denature.
Same water potential-prevent osmosis, so no shrinkage of organelles
Homogenisation and ultracentrifugation how to separate
Break open cells .
Remove larger debris by filtration.
Centrifuge highest density organelle nuclei obtained as pellet at slowest speed.
Mitochondria in 2n pellet as less dense than nucleus
Why scientist can use detergent to break open cells instead of homogenisation
Cell membrane made from phospholipid.
Detergent dissolves phospholipid belayer
