Microscopy

Question 1

Magnification formula

Answer 1

Size of image / size of real object

Question 2

Magnification definition

Answer 2

How many times bigger the image is compared to object

Question 3

Resolution definition

Answer 3

Minimum distance apart two objects can be in order for them to appear as two separate objects.

Question 4

Cell fractionation solution properties and why

Answer 4

Cold - reduce enzyme activity that could break down organelles
Same water potential of tissue - prevent organelles bursting/shrinking by osmosis
Buffered - so pH does not fluctuate which can alter structure of organelles

Question 5

Cell fragmentation two steps

Answer 5

Homogenation - blending of cells to release organelles AND THEN FILTER
Ultracentrifugation - fragments in filtered homogenate are separated by spinning at high speed.

Question 6

Ultracentrifugation of animal cell steps

Answer 6

• Filtrate spun at slow speed. Nuclei forced to bottom and supernatant removed.
• Supernatant spun again but faster. Mitochondria then removed and process repeats.

Question 7

Electron microscope advantages

Answer 7

Wavelength of electron beam is smaller than wavelength of light, higher resolving power.
Beam is negatively charged so can be focused by electromagnets.

Question 8

TEM (transmission electron microscope) disadvantages

Answer 8

Must be in vacuum so living specimens cannot be viewed.
Complex staining process.
Greyscale image.
Thin specimen necessary for electron penetration.
Artefacts can be observed.

Question 9

SEM (scanning electron microscope) disadvantages

Answer 9

Must be in vacuum so living specimens cannot be viewed.
Complex staining process.
Greyscale image.
Thin specimen NOT necessary for electron penetration but lower resolving power.
Artefacts can be observed.