2.1.1. Cell structure - (Microscopes)

Question 1

Definition of magnification

Answer 1

the number of times an image appears larger compared to the actual size of the object

Question 2

What formula is used to calculate Magnification?

Answer 2

The triangle is Observed size/ Actual size X Magnification

Question 3

Convert:
Centimeter (cm)
Millimeter (mm) to 
Micrometer (um)to 
Nanometer (nm)

Answer 3

Centimeter X 10 to
Milimeter X 1000 to
Micrometer X 1000 to
Nanometer

Question 4

Definition of resolution

Answer 4

the ability to distinguish between two different points

Question 5

Best resolution of a light microscope

Answer 5

0.2 micrometres

Question 6

Best magnification of a light microscope

Answer 6

x1500

Question 7

What are Light microscope mainly used to look at?

Answer 7

To look at whole cells or tissues

Question 8

How does a light microscope work?

Answer 8

> They use light and several lenses in order to magnify.

> Specimens are illuminated with light which is focused using glass lenses

Question 9

Advantages of a light microscope

Answer 9

> Cheap
Easy to use
Can examine living things

Question 10

Disadvantages of a light microscope

Answer 10

> Specimens have to be small, thin and transparent

> Have a low resolution due to light

Question 11

How does a confocal scanning microscope work?

Answer 11

> They use laser lights to scan a specimen thats usually tagged with fluorescent dyes.
The laser beam which is focused through a lens is aimed at a beam splitter
This splits the beam and some of the light to the specimen
When the laser hits the dyes it causes them to give off fluorescent light
This light is then focused through a pinhole onto a detector which is hooked up to a computer, which generates an image.

overall use laser light to scan an object point by point and assemble, by computer, the pixel information into one image

Question 12

What does a pinhole for laser scanning microscope do?

Answer 12

The pinhole means that any out-of-focus light is blocked, so these microscopes produce a much clearer image

Question 13

Advantages of a confocal scanning microscope

Answer 13

> Builds a clean 3d image
Can look at objects at different depths in thick specimens
Images are high resolution

Question 14

Disadvantages of a confocal scanning microscope

Answer 14

> Quite big

> Doesn’t always show full sample

Question 15

Best resolution of a confocal scanning microscope

Answer 15

20 nanometres

Question 16

Best magnification of a confocal scanning microscope

Answer 16

x1500

Question 17

How does a TEM Microscope work?

Answer 17

> They use elctromagnets to focus a beam of electrons which is then transmitted through the specimen to produce a 2D image.
Denser parts of the specimen absorb more elections, which makes them look darker on the image.

Question 18

Advantages of TEM

Answer 18

> Can look at small organelles

> High resolution

Question 19

Disadvantages of TEM

Answer 19

> Can only be used on thin specimens
Angles at which the specimen is cut can affect how they appear
Specimen are dead as they must be viewed in a vacuum

Question 20

Best resolution of TEM

Answer 20

0.0002 micrometres or 0.2 nm

Question 21

Best magnification of TEM

Answer 21

more than 1,000,000

Question 22

How does a SEM work?

Answer 22

They scan a beam of electrons across the specimens. This knocks off electrons from the specimen, which are gathered in a cathode ray tube to form an image.

Question 23

Advantages of a SEM

Answer 23

produces a 3D image

Question 24

Disadvantage of SEM

Answer 24

> Have a lower resolution than TEMs
Specimens are dead as they must be viewed in a vacuum
Only shows the surface of cells

Question 25

Best resolution of SEM

Answer 25

0.002 micrometres

Question 26

Best magnification of SEM

Answer 26

less than 500,000

Question 27

Similarities of SEM & TEM

Answer 27

> Both are large and very expensive

> Need a great deal of skills and trainning to use