Methods of Studying Cells

Question 1

What are the 3 types of microscopes?

Answer 1

Optical, Transmission Electron Microscope, Scanning Electron Microscope

Question 2

What is the definition of magnification?

Answer 2

How many times larger an image is compared to an object.

Question 3

What is the definition of resolution?

Answer 3

The minimum distance between 2 objects in which they can still be viewed as separate.

Question 4

What are the differences between an optical and electron microscope?

Answer 4

Optical:
Beam of light condensed to create an image (lens)
Poorer resolution; light has longer wavelength (small organelles in a cell are not visible)
Lower magnification
Colour images
Living samples

Electron:
Beam of electrons condensed to create an image - electromagnets
Higher resolution; electrons have a shorter wavelength
Higher magnification
Black and white images
Samples in vacuum, not living

Question 5

What are the differences between a transmission electron microscope (TEM) and a scanning electron microscope (SEM)?

Answer 5

TEM:
Extremely thin specimens in vacuum
Beams of electron passes through specimen; some absrob the elctrons so become darker
2D image

SEM:
Does not need to be thin
Electrons are not passing through; beamed onto surface + scattered
3D image

Question 6

What is the magnification equation acronym and what does it stand for?

Answer 6

I AM
Image size = Actual size x Magnification

Question 7

What is the purpose of the eye piece graticule?

Answer 7

Used to measure the size of an object viewed on a microscope slide

Question 8

What is the purpose of cell fractionation?

Answer 8

It isolated different organelles so they can be studied further seperately.

Question 9

What 3 things does the solution need to be in cell fractionation and why?

Answer 9

Cold - reduces enzyme activity; no damage to organelles
Isotonic - same water potential to prevent osmosis; could cause organelles to burst
Buffered - pH buffer prevents damage to organelles

Question 10

What is homogenisation?

Answer 10

Cells being broken open using a blender - cold, isotonic, buffered solution

Question 11

What is differential centrifugation?

Answer 11

Centrifugal forces cause pellets of most dense organelles to form at the bottom of the test tube, the organelles will seperate at different speeds according to their densities.

Question 12

Describe the process of cell fractionation.

Answer 12

1. Homogenisation (cells broken up using blender to release organelles
2. Filter to remove large cell debris
3. Sample into centrifuge; at different speeds - organelles will seperate according to densities.

Question 13

What is the order in which the organelles will seperate?

Answer 13

1. Nuclei
2. Chloroplast
3. Mitochondria
4. Lysosomes
5. Endoplasmic reticulum
6. Ribosomes