Microscopes

Question 1

Light microscope

Answer 1

• Specimen image enlarged, inverted, and viewed using light from the light source
• 1000x mag
• Relies on visible light
• Observe living + non-living cells
• Resolution 200 nm

Question 2

Gram staining

Answer 2

• Gram pos: purple: thicker cell wall
• Gram neg: pink: thinner cell wall

Question 3

Electron microscope

Answer 3

• Electron beam focused using electromagnets replaces light in producing image
• 0.5 nm resolution due to extremely short wavelength of electron beam
• Up to 5x10^5 magnification

Question 4

Transmission Electron microscope (TEM)

Answer 4

• Uses electron beams instead of light, a type of Electron microscope. Scattering of electron particles used to detect pattern.
• Specimen treated with chemical fixatives, bombarded with heavy metal atoms, embedded into plastic and cut into thin 50-100 nm slices
• Preparation kills specimen, dead specimens only
• Resolution limit 0.05 nm
• 50 million mag

Can see inside specimen

Question 5

Scanning Electron microscope (SEM)

Answer 5

• Electron beams instead of light
• Electron beam scans surface of specimen. TV monitor records patterns arising from surface variations to produce detailed 3D view of specimen surface
• 5x10^5 mag (same as regular electron microscope)
• Resolution 0.5 nm (same as regular electron microscope)

Only sees outside of specimen

Question 6

SEM magnification and resolution

Answer 6

Magnification: 5x10^5 x
Resolution: 0.5 nm