the microscopes

Question 1

what are the 5 cell theories ?

Answer 1

1. Cell is the basic unit of structure and function of living things
2. All living organisms made up of cell/ cells
3. Metabolic processes occurs within cells
4. New cells derived from existing cells
5. Cells have genetic materials that are passed on

Question 2

which microscope is the more high tech one

Answer 2

electon microscope

Question 3

why is the electron a very suitable source of radiation for microscopy?

Answer 3

1) Extremely short wave length
– 1nm

2) Easily focused with electromagnets
– negatively charged

Question 4

define magnification, give its formula

Answer 4

= the number of times larger an image than the real size of the object

M= I/A

I= IMAGE SIZE
A= ACTUAL SIZE

Question 5

define resolution

Answer 5

the ability to distinguish between two objects very close together.
(the greater the resolution, the greater the details can be seen)

Question 6

formula for resolution

Answer 6

(1/2)(wavelength)

Question 7

explain why it is possible to see the internal membranes of a cell in electron micrograph, but it is not possible to see then when using the light microscope

Answer 7

• EM has greater resolution
• resolution is ability to differentiate between two points
• resolution is equal to half of wavelength
• resolution of LM is 200nm while EM is 0.5nm

Question 8

sources of radiation in LM and EM?

Answer 8

LM - light

EM - electron (in vacuum condition)

Question 9

lenses in LM and EM?

Answer 9

LM - glass

EM - electromagnet

Question 10

magnification in LM and EM?

Answer 10

LM - x1500

EM - x500 000

Question 11

maximum resolution in EM and LM?

Answer 11

LM - 200nm

EM - 0.5nm

Question 12

specimens used in LM?

Answer 12

living and non-living things

microtome used

Question 13

specimens used in EM?

Answer 13

non-living cells, dehydrated, ultra thin

ultramicrotome used

Question 14

why cant you observe living things in the EM?

Answer 14

(google answer, do update)

electrons will damage the samples

Question 15

stains in LM?

Answer 15

Coloured dyes

Question 16

stains in EM?

Answer 16

Heavy metals (to reflect electrons)

Question 17

colour of image in LM and EM?

Answer 17

LM - Coloured

EM - B&W

Question 18

suggest one disadvantage of the electron microscope compared to the light microscope for the study of cells

Answer 18

• only dead specimens can be viewed
• requires more electrical power
• difficult to operate (requires technical training)
• sensitive to external magnetic fields

Question 19

state the advantages of using LM rather than EM in the studies of tissues

Answer 19

• can observe living tissue (observe processes like mitosis)
• lower cost of maintenance
• see actual colour