1 Cell theory & microscopy Flashcards
Size of typical cell?
2-200um in diameter.
Cell theory states: point 1
1 All organsims composed of one or more cells
Cell theory states: point 2
2 Cells are the smallest units of life, basis of ogansization of all living organsims.
Cell theory states: point 3
3 Cells arise only by division of pre-existing cell.
Cells are the ________ units of life.
Smallest
What does microscopy do?
Produces enlarged image through magnification.
Difference betwee magnification and resolution?
Magnification refers to the increase in size of an object.
Resolution refers to distinguish two points at seperate.
What’s light microscopy?
Beam of light, focused by condensor.
Light microscopy - resolution.
0.2um
Light microscopy - magnification.
1000x
Label a microscope
xxx
5 types of light microscopy:
Bright field. Phase contrast. DIC. Fluorescene. Confocal.
What’s Brightfield? (4 points)
Classic. Poor contast. Staining of killed cells often required. Cells are fixed.
What’s Phase contast? (3 points)
Uses differences in RI of cell components to imprive contrast. Good for living cells. Cells are live and fixed.
What’s DIC? (4 points)
Utilises rate of chnage in RI. Produces apparent 3D images. Can be thick & unstained. Cells are live and fixed.
What’s Fluorescene microscopy? (4 points)
Specimen stained with fluorescent dye/protein and excite with UV light. Produces high contrast against dark background. GFP from jellyfish. Cells are alive and fixed.
GFP
Green fluorescent protein.
What’s Confocal scanning light microscopy?
Thick. No sectioned. 300um in depth. Laser beam scans planes with fluorescene. Constructed to 3D. Cells are alive.
3 steps for preparing sections of specimen.
Thin slices (10um) by fixation, embedding, sectioning and staining.
What can a light microscope see? (5 items)
Most animal & plant cells. Most bacteria. Nuclues. Mitochondria.
What can an e- microscope see? (6 items)
Smallest bacteria. Viruses. Ribosomes. Proteins. Lipids. Small molecules.
4 steps of Transmission e- microscope freeze fracture process.
1 Fracturing. 2 Etching. 3 Shadowing 4 Replicating. xxx
Two types of e- microscopy.
Transmission and Scanning.
What is e- microscopy?
Uses a beam of e-, not light.
E- microscopy reolution is:
2-20nm.
Transmission e- microscopy.
E- passes through thin specimens. Specimens: 1 fixed, sectioned, dehydrated and stained with heavy metals OR 2 cyrofixed and freeze fractures with heavy metals (to reveal internal cell surfaces).
TEM magnification:
1,000,00x
Scanning e- microscopy.
E- beam scanned over specimen and back scatter strikes a detector. Apparent 3D image. Samples fixed, dehydrated and coated with thin layer of gold.
Magnification SEM:
150,000X
Resolution SEM:
10nm.
Cyro-e- microscopy.
Less harsh. Uses frozen molecules in solution. More gentle e- beams to determine biomolecule structure.
Super-resolution microscopy.
Fluorescene based. Ovecoming light resolution limit. Resolution: 100nm.
Atomic Force Microscopy.
Visulises surface at molecular scale. Fine pointed tip, linked to cantilever arm. Detects fine movement, reflected on laser beam.
