2.1.1 Cell Structure – Microscopes

Question 1

How do you calculate the total magnification of a light microscope?

Answer 1

Total magnification = magnification of objective lens x magnification of eye piece lens

Question 2

What are the 4 different types of microscopes?

Answer 2

1. Light (optical) microscope
2. Transmission electron microscope (TEM)
3. Scanning electron microscope (SEM)
4. Laser scanning (confocal) microscope

Question 3

What is differential staining?

Answer 3

• Stain only binds to specific cell structures
• Different structures have different colours to be identified

Question 4

Why are stains needed to view a specimen?

Answer 4

1. Stains increase contrast
2. To distinguish (what your looking for) clearly

Question 5

By what type of transport are stains taken up by a specimen?

Answer 5

Active transport

Question 6

Which stain is known as an all-purpose stain?

Answer 6

Methylene blue

Question 7

Which stain stains DNA dark red?

Answer 7

Acetic orcein

Question 8

Which stain stains plant cell walls yellow/orange?

Answer 8

Iodine

Question 9

What is the maximum magnification of a light microscope?

Answer 9

x1500

Question 10

What is the maximum resolution of a light microscope?

Answer 10

200nm

Question 11

What is the maximum magnification of a TEM?

Answer 11

x500,000

Question 12

What is the maximum resolution of a TEM

Answer 12

0.5nm

Question 13

What is the maximum magnification of a SEM?

Answer 13

x200,000

Question 14

What is the maximum resolution of a SEM

Answer 14

5nm

Question 15

Give two advantages of working with light microscopes.

Answer 15

• Cheap
• Can view an organism live/dead
• Portable – can be used in the field
• Simple sample preparation

Question 16

Give two disadvantages of working with light microscopes.

Answer 16

• Poor magnification x1500
• Poor resolution 200nm
• Long wavelength of light

Question 17

Give two advantages of working with TEM

Answer 17

• 2D image
• use a beam of electrons with short wavelength
• High magnification x500,000
• High resolution 0.5nm

Question 18

Give two disadvantages of working with TEM

Answer 18

• expensive
• only view specimen dead
• specimen must be thin
• need a vacuum to see
• complex staining process
• may contain artefacts

Question 19

What is an artefact?

Answer 19

• An artefact is a structure which may appear in the specimen during the preparation
  e.g. air bubble
• This will then change the ultrastructure of a cell

Question 20

Give two advantages of working with TEM

Answer 20

• 3D image
• specimen does not have to be thin
• use a beam of electrons with short wavelength
• High magnification x200,000
• High resolution 5nm

Question 21

Give two disadvantages of working with TEM

Answer 21

• expensive
• only view specimen dead
• need a vacuum to see
• complex staining process
• may contain artefacts