Lecture 1- cell theory and methods to study cells

Question 1

Magnification

Answer 1

A larger version of a image

Question 2

Resolution

Answer 2

The ability to tell apart different parts of an image

Question 3

Light microscopy: bright field

Answer 3

Absorption of visable light
Light basorbing stains on thin specimen
Live cells:no
Fixed cells: yes

Question 4

Light microscopy: Phase contrast

Answer 4

Variations of thickness and refractive index in specimen
Requires relatively flat cells
Live cells: yes
Fixed cells: yes

Question 5

Light microscopy: differential interference contrast (DIC)

Answer 5

Gradient of refractive index
No specific requirements
Live cells:yes
Fixed cells: yes

Question 6

Light microscopy: Fluorescence microscopy

Answer 6

Emmision of light by fluorescent molecule
Cellular molecules labelled with fluorecent dyes
Live cells: yes
Fixed cells: yes

Question 7

Producing sections for microscopy

Answer 7

Approx10 micrometers depth
prepared by fixation, embedding, sectioning and staining

Question 8

Light microscopy: confocal scanning microscopy

Answer 8

Allows examination of thicker specimens approx 300 micrometers
Laser beam scans successive single points
Treated with fluorscent stain
Then reconstruct 3D images
Good for living cells

Question 9

Freeze fracture

Answer 9

Requires heavy metals
Revals internal structure

Question 10

Electron microscopy: Transmission electrom microscopy (TEM)

Answer 10

Electrons pass through very thin specimens
Differential absoption of electrom beams
Magnification up to 1,000,000x
Specimens fixed, sectioned, dehydrated and stained with heavy metals
Reveqals internal cell surfaces
Done under vacuum

Question 11

Electron microscopy: Scanning electron microscopy (SEM)

Answer 11

Electron beam scanned over specimen
Back scatter strikes a detector
Produces 3D image
Resolution 10nm
Samples fixed, dehydrated and coated with a thin layer of metal

Question 12

Cryo-electron microscopy

Answer 12

Less harsh
Deepfrozen molecules
Gentle electrom beams

Question 13

Super-resolution microscopy

Answer 13

Fuorescence based
allows resolution 100nm

Question 14

Atomic Force Microscopy (AFM)

Answer 14

Visualise surfaces at molecular scale
Fine pointed tip linked t cantilever arm
Moves across surface
Movement detected by laser beam

Question 15

Size of a typical cell

Answer 15

2-200 micrometers

Question 16

3 parts of cell theory

Answer 16

1. All organisms composed of 1 or more cells
2. Cells are smallest unis of life
3. Cells arise by division of a pre-existing cell