microscopy

Question 1

what are microscopes used for

Answer 1

observe and investigate cell structure

Question 2

what are the 2 different types of microscopes

Answer 2

light microscope + electron microscope

Question 3

how do light microscopes work

Answer 3

using light rays
light is directed through the thin layer (finish this)

Question 4

what are the disadvantages of light microscopes

Answer 4

• low resolution - maximum resolution = 0.2 micrometers
• low magnification - maximum useful magnification = x1500
• can only be used to observe larger structures eg. entire cells, nuclei, mitochondria + chloroplasts

Question 5

what are the advantages of light microscopes

Answer 5

• small, portable + relatively cheap
• specimen preparation can be straightforward = doesn’t use harsh chemicals + easy to set up + use
• produces colour images
• allow the observation of living specimens

Question 6

how do electron microscopes form an image

Answer 6

by using electrons

Question 7

what are the 2 types of electron microscope

Answer 7

transmission electron microscopes
scanning electron microscopes

Question 8

how do transmission electron microscopes work

Answer 8

use electromagnets to transmit a beam of electrons through a specimen, stained with metal salts.
denser parts of the specimen absorb more electrons, meaning that denser parts appear darker on the final image

Question 9

what are the advantages of a transmission electro microscope

Answer 9

• high magnification of up to x2 million
• new generation being developed that magnifies up to x50 million
• allow internal structures to be seen

Question 10

what are the disadvantages of the transmission electron microscope

Answer 10

• the specimen has to be chemically fixed, dehydrated + stained - may be hazardous for the user = specimens have to be dead, as they are viewed in a vacuum.
• large + very expensive
• need a great deal of skill + training to use
• produces a black + white image

Question 11

transmission electron microscopes produces images that are:

Answer 11

high-resolution
2-dimensional
shows the internal structures
black + white image

Question 12

how do scanning electron microscopes work

Answer 12

pass a beam of electrons across the surface of a specimen and then detect the rate at which the electrons bounce back, reflecting off the tissues.

Question 13

scanning electron microscopes produces images that:

Answer 13

are 3-dimensional
show the surface of specimens
black + white image

Question 14

what are the advantages of scanning electron microscopes

Answer 14

• high magnification = up to x5 million
• high resolution
• can see details of the surfaces of structures

Question 15

what are the disadvantages of a scanning electron microscope

Answer 15

• the specimen has to be chemically fixed, dehydrated + stained - may be hazardous to the user = specimens have to be dead, as they are viewed in a vacuum.
• large + very expensive
• need a great deal of skill + training to use
  -black + white image

Question 16

how does a laser scanning confocal microscope work

Answer 16

uses a laser beam of light to illuminate chemical stains within the specimen

Question 17

what are the advantages of a laser scanning confocal microscope

Answer 17

• can see living cells
• can observe cell processes by tracking molecules
• higher resolution than light microscopes

Question 18

what are the disadvantages of a laser scanning confocal microscope

Answer 18

• more expensive + complex than a light microscope