Microscopes

Question 1

What is the equation that links image size, magnification and real size?

Answer 1

Magnification= image size/ real size

Question 2

Define magnification

Answer 2

how many times bigger the image is when compared to the object

Question 3

Define resolution

Answer 3

minimum distance apart 2 objects can be to appear as separate items

Question 4

What is the link between light and resolution

Answer 4

Longer wavelength than electrons so limited resolution

Question 5

What is the limit of a light and electron microscope?

Answer 5

light= 0.2 micrometres

electron=0.1 nanomentres

Question 6

What is the equation of the mitotic index?

Answer 6

number of dividing cells in field of view/ number of cells in total

Question 7

Define cell fractionation

Answer 7

process where cells are broken up and the different organelles they contain are separated out

Question 8

Describe homogenation

Answer 8

homogeniser breaks up cells to release the organelles
resultant fluid= homogenate
filter to remove debris and large cell chunks

Question 9

Define ultracentrifugation

Answer 9

process by which the fragments in the filtered homogenate are separated in a machine called a centrifuge.

Question 10

What speed are \_\_\_\_\_\_ spun at?
Nuclei 
Lysosomes
Chloroplast
Mitochondria
Ribosomes

Answer 10

nuclei= 1000
mitochondria= 3500
lysosomes= 16500
ribosomes=100,000

Question 11

Name the two types of electron microscopes

Answer 11

Transmission electron microscope

Scanning electron microscope

Question 12

What is the resolving power of the TEM and why is this not often achieved in practise?

Answer 12

0.1 nm
higher electron beam required which can destroy the specimen
difficulty in preparing the specimen

Question 13

What are the main limitations of the TEM

Answer 13

specimen must be extremely thin
whole system must be in a vacuum hence the specimen must be dead
complex staining process is required but image is not in colour
image may contain artefacts

Question 14

What are the main limitations of the TEM

Answer 14

specimen must be extremely thin
Image is 2D ( can build 3D via many images which is slow and complicated)
whole system must be in a vacuum hence the specimen must be dead
complex staining process is required but image is not in colour
image may contain artefacts

Question 15

What are the limitations of the SEM?

Answer 15

whole system must be in a vacuum hence the specimen must be dead
complex staining process is required but image is not in colour
image may contain artefacts

Question 16

Name the resolution power of the SEM

Answer 16

20nm

Question 17

Compare the optical and TEM microscope

Answer 17

1. TEM use electrons and optical use light;
2. TEM allows a greater resolution;
3. (So with TEM) smaller organelles/named cell
   structure can be observed
   OR
   greater detail in organelles/named cell structure
   can be observed;
4. TEM view only dead/dehydrated specimens and
   optical (can) view live specimens;
5. TEM does not show colour and optical (can);
6. TEM requires thinner specimens;
7. TEM requires a more complex/time consuming
   preparation;
8. TEM focuses using magnets and optical uses
   (glass) lenses;