(3.2.1.3) methods of studying cells

Question 1

how do you measure objects using an eyepiece graticule?

Answer 1

1. use eyepiece graticule to measure the object, for example nucleus or capillary
2. calibrate eyepiece graticule against stage micrometer
3. take a number of measurements and calculate the mean

Question 2

what are some advantages and limitations of a TEM (transmission electron microscope)?

Answer 2

advantages:
1. small objects can be seen, like ribosomes
2. TEM has high resolution as wavelength of electrons shorter

limitations:
1. cannot look at living cells as cells must be in a vacuum
2. must be thin specimen
3. preparation may create artefact
4. does not produce colour image

Question 3

compare a transmission electron microscope with a optical (light) microscope?

Answer 3

1. TEM uses electrons whereas optical uses light
2. TEM allows a greater resolution so with TEM, smaller organelles can be observed
3. TEM view only dead/dehydrated specimens whereas optical (can) view live specimens
4. TEM does not show colour whereas optical (can)
5. TEM requires thinner specimens therefore requires a more complex/time consuming preparation
6. TEM focuses using magnets whereas optical uses (glass) lenses