Microscopes

Question 1

What are the 3 types of microscopes

Answer 1

Optical microscopes
Transmission electron microscope
Scanning electron microscope

Question 2

Define magnification

Answer 2

How many times larger the image is compared to the object

Question 3

Define resolution

Answer 3

The ability to distinguish between 2 objects that are close together- higher resolution means more detail

Question 4

How is the resolution of an optical microscope determined

Answer 4

By the wavelength of light

Question 5

How is the resolution of both an transmission and scanning electron microscope determined

Answer 5

The wavelength of the beam of electrons

Question 6

Why does electron microscopes have a higher resolution then optical microscopes

Answer 6

The wavelength of beam of electrons is much shorter so they have a higher resolution so the distance between the 2 objects is smaller

Question 7

What is the equation of magnification

Answer 7

Image size/actual size

Question 8

Conversation of units

Answer 8

M.
X1000 /1000
MM.
X1000 /1000
uM.
X1000 /1000
NM.

Question 9

How do u convert mm to cm

Answer 9

/10

Question 10

What is an eyepiece graticule used for

Answer 10

To measure the size of objects viewing under the microscope

Question 11

What is cell fractionation

Answer 11

To isolate organelle so they can be studied

Question 12

What do you do before the cell fractionation process

Answer 12

• separate cell organelles by cell fractionation
  -solution must be kept in a cold,isotonic,buffered solution

Question 13

In cell fractionation why does the solution have to be cold

Answer 13

To reduce enzyme activity as when cell breaks enzymes are released
This may damage organelles

Question 14

In cell fractionation why does the solution have to be isotonic

Answer 14

So there is no osmosis ad it must have the same water potential so organelles don’t shrivel shrink and burst

Question 15

In cell fractionation why does the solution have to be buffered

Answer 15

So PH is constant and dosnt denature enzymes and damage organelles

Question 16

Describe the process of cell fractionisation- 1st step homogenisation

Answer 16

Homogenisation
- the cell must be homogenised using a blender breaking open cells to release contents / organelle’s
-place in cold,buffered,isotonic solution
-filter homogenate to remove large debris

Question 17

What is the second process of cell fractionation and explain

Answer 17

Ultracentrifugation
- centrifuge homogenate in a tube at a low speed
● Remove pellet of heaviest organelle and respin supernatant
at a higher speed
● Repeat at increasing speeds until separated out, each time the
pellet is made of lighter organelles

Question 18

What is the order of density’s in centrifugation stage of ultracentrifugation in cell fractionation from most dense to least dense

Answer 18

1. Nuclei
2. Chloroplast ( if using plant tissue)
3. Mitochondria
4. Lysosomes
5. Endoplasmic reticulum
   6.ribosomes

Question 19

what are the principles of an optical microscope

Answer 19

Light focused using glass lenses
Light passes through specimen, different structures absorb different amounts & wavelengths
Generates a 2D image of a cross-section
Low resolution due to long wavelength of light
Can’t see internal structure of organelles or ribosomes
Specimen = thin
Low magnification (x 1500) Can view living oranisms
Simple preparation
Show colour

Question 20

What are the principles of a transmission electron microscope

Answer 20

Electrons focused using electromagnets
Electrons pass through specimen, denser parts absorb more and appear darker
Generates a 2D image of a cross-section
Very high resolution due to short wavelength of electrons
Can see internal structures of organelles and ribosomes
Specimen = very thin
High magnification (x 1,000,000)
Can only view dead specimens as uses a vacuum
Complex preparation so artefacts often present
Does not show colour
Expensive

Question 21

What are the principles of scanning electron microscope

Answer 21

Electrons focused using electromagnets
Electrons deflected / bounce off specimen surface
Generates a 3D image of surface
High resolution due to short wavelength of electrons
Can’t see internal structures Specimen does not need to be thin
High magnification (x 1,000,000)
Can only view dead specimens as uses a vacuum Complex preparation so artefacts often present Does not show colour