Cell Structure:microscopes

Question 1

outline how a student could prepare a temporary mount of tissue for a light microscope

Answer 1

1. use thin section of tissue
2. place plant tissue in a drop of water
3. stain tissue on a slide so structures visible
4. add coverslip at 45 degrees to stop air bubbles

Question 2

describe how light microscopes work

Answer 2

lenses focus rays of light and magnify the thin slice
different structures absorb different amounts of light and wavelengths
reflected light is transmitted to the observer via the objective lens and eyepiece

Question 3

describe how TEM works

Answer 3

pass a high energy beam of electrons through a thin slice of specimen more dense structures appear darker as absorb more electrons focus image onto fluorescent screen

Question 4

describe how a scanning electron microscope works

Answer 4

focus a beam of electrons using electromagnetic lenses
reflected electrons hit collecting device and are amplified to produce an image

Question 5

describe how a laser scanning confocal microscope works

Answer 5

focus laser beam onto sample using objective lens
fluorophores emit photons
photomultiplier tube amplifies signal onto a detector

Question 6

define magnification

Answer 6

factor by which the image is larger than the specimen

Question 7

define resolution

Answer 7

smallest separation distance at which 2 structures can be distinguished

Question 8

why do samples need to be stained for light microscopes

Answer 8

coloured dye binds to the structure
facilitates absorption of wavelengths of light to produce image and allows distinguishable between structures

Question 9

what is the magnification and resolution of compound optical microscope

Answer 9

magnification= x2000
resolution= 200nm

Question 10

state the magnification and resolution of TEM

Answer 10

magnification= x500,000
resolution=0.5nm

Question 11

state the magnification and resolution of scanning electron microscope

Answer 11

magnification= x500,000
resolution= 3-10nm