Fundamentals And Microscopy Flashcards
(19 cards)
What are the oldest known fossils?
Stromatolites - accumulation of sedimentary layers of bacterial mats - 3.5 billion years old.
How long time ago the life on Earth only consisted from prokaryotes?
3.5-2.1 billion years ago.
Do all organisms have the common ancestry?
Yes, it was an ancestral prokaryote called LUCA. All living organisms have very similar basic biochemistry.
Plants, animals and fungi are more related to archaea. Eukaryotic ancestor got mitochondria from an ingested bacteria more than 1.5 billion years ago.
Plant ancestor engulfed photosynthetic bacteria in addition to mitochondria much later.
What are cells essentially?
Self-replicating collection of catalysts.
What organisms are the most diverse and numerous?
Prokaryotes (bacteria and archaea).
They colonised every habitat on the planet.
Can prokaryotes form multicellular organisms?
Yes, for example Anabaena cylindrica forms simple long chains of multiple prokaryotic cells. Cells already have some specialisation (some to capture nitrogen, some to capture carbon dioxide, some to make spores).
Can prokaryotes have intracellular membranes?
Yes, for example, in Phormidium laminosum to increase surface area for photosynthesis.
Who used microscopy for the very first time?
Hooke at 1665; he discovered cells.
Leeuwenhoek at 1674; discovered protozoa and bacteria 9 years later.
Who did discover nucleus and mitochondria?
Brown at 1833; discovered nucleus at orchids.
Kolliker at 1857; discovered mitochondria in muscle cells.
What is the biggest resolution possible for a light microscope?
200 nm (0.2 microns); up to 1000X magnification. This is due to light wavelength.
How does light travel through light microscope?
1) Light source
2) Condenser lens
3) Specimen on glass slide
4) objective lens
5) tube lens
6) eyepiece
What are the 3 types of settings in light microscopy?
- bright-field (normal, simplest, plain)
- phase-contrast (different densities correspond to different shading)
- interference-contrast (to make it look more 3D)
What is fluorescence microscopy?
Type of light microscopy, where the light from the light source is filtered to obtain a narrower range of wavelength (corresponding to a fluorescent dye).
How the light passes:
1) Filter #1 near light source
2) beam-splitting mirror
3) objective lens
4) specimen
5) filter #2 blocks the rest of light which is not emitted by dye itself.
Result: bright object at dark background.
What is the most common dye in fluorescent microscopy?
Green fluorescent protein (GFP).
What is light sheet fluorescence microscopy?
Very thin beam of laser light (“sheet”) to illuminate only a thin slice of a specimen from its side. Gives much detailed images than conventional light microscopy.
What is super resolution fluorescence microscopy?
Uses 2 lasers of the different wavelength, one of them (central) excites fluorescent dye on certain spot, another (surrounding central) switches off dye in the rest of the area.
Can reach unbelievable for light microscopy maximum resolution of 20 nm (10 times different from the normal 200 nm).
How does scanning electron microscopy work?
How the beam of electrons pass (all lens are magnetic coils):
1) Electron gun
2) Condenser lens
3) Beam deflector from scan generator
4) objective lens
5) electrons hit specimen and scatter away from it
6) this is caught by detector, connected to the video screen.
This produces a 3D image with resolutions 3-20 nm.
How does transmission electron microscopy work?
How electron beam travels:
1) electron gun
2) condenser lens
3) specimen
4) objective lens
5) projector lens
6) viewing screen
This produces 2D image, with 1 nm resolution (million times magnification).
What is the difference in preparation of specimens for the scanning and transmission electron microscopy?
For scanning: specimen is coated with a very thin layer of a heavy metal.
For transmission: specimen in cut into ultrathin samples and they are stained with heavy metals. The sample is shrunk and placed in vacuum.
