2.1.1 Cell Structure - Microscopy

Question 1

Who designed the early microscope?

Answer 1

Robert Hooke (1660s)

Question 2

Magnification Definition

Answer 2

the number of times
larger
an image is compared to the
object itself

Question 3

Resolution

Answer 3

the ability to distinguish 
clearly
between 2 points 
that are 
very close together

Question 4

Fluorescent Dye

Answer 4

put on a thin section

to make a 3D image

Question 5

Light Microscope:
wavelength
resolution
max magnification
staining
image
specimens
ease of use
expense

Answer 5

400nm - [wavelength]
Low, 200nm - [resolution]
x1500 - [max magnification]
coloured chemicals or fluorescent dyes - [staining]
natural colour of objects - [image]
living or non living - [specimen]
easy to use - [ease of use]
relatively cheap - [expense]

Question 6

Electron Microscope:
wavelength
resolution
max magnification
staining
image 
specimens
ease of use
expense

Answer 6

Electron beam, 0.4nm - [wavelength]
high, (TEM) 0.2nm (SEM) 3 - 10nm - [resolution]
(TEM) x500 000 (SEM) x100 000 - [max magnification]
salts of heavy metal ions - [staining]
black and white - [image]
non living as specimen is put in a vacuum - [specimen]
difficult - [ease of use]
very expensive - [expense]

Question 7

SEM:
resolution
magnification
electron beam
image

Answer 7

3 - 10nm - [resolution]
x100 000 - [magnification]
BOUNCES off the surface of the sample - [electron beam]
black and white 3D image - [image]

Question 8

TEM:
resolution
magnification
electron beam
image

Answer 8

0.2nm - [resolution]
x500 000 - [magnification]
passes THROUGH the sample - [electron beam]
2D image - [image]

Question 9

Preparing permanent sections for viewing:

• Fixing
• Sectioning
• Staining
• Mounting

Answer 9

1. Fixing - chemicals used to preserve specimens (formaldehyde)
2. Sectioning - dehydrated (alcohols), put in mould with wax or resin(hard block), sliced thinly with knife
3. Staining - coloured chemicals / fluorescent dyes to make specimens visible
4. Mounting - on an angle to prevent air bubbles (mount needs to be wet)

Question 10

Differential Staining

Answer 10

distinguish between 2 types of organisms

OR

different organelles within an organism
(gram staining)

Question 11

Formaldehyde

Answer 11

preserves all cells

Question 12

Acetic Orcein

Answer 12

stains
DNA
dark red

Question 13

Methylne Blue

Answer 13

stains nucleus

Question 14

Why must specimens be thin?

Answer 14

so light can get through

Question 15

Why is resolution limited in light microscopy?

Answer 15

light has a certain wavelength

light is the limiting factor

Question 16

Eyepiece Graticule

Answer 16

fitted onto the eyepiece
like a transparent ruler
when you look through
you see a scale

Question 17

Stage Micrometer

Answer 17

placed on the stage
this is the microscope slide with an
accurate scale

Question 18

How do you find the scale?

eyepiece graticule and stage micrometer

Answer 18

scale = stage micrometre scale / the amount of divisions in the eye piece graticule

Question 19

Magnification Equation

Answer 19

magnification = image size / actual size
M = I / A

THINK:
MIA
1mm = 1000um (micrometre)