2.1.1 Microscopy Flashcards
Name some cell theories
-Cells are the basic unit of all organisms
-Cells multiply by dividing
-Energy flows occur within cells
-DNA passes from cell to cell
-All cells have the same basic chemical composition
DEVELOPING MICROSCOPES
What was Hookes contribution to microscopy ?
1665 - Hooke used the first microscope and “discovered” cells although he could only see the cell membrane
What was Leeuwenhoeks contribution to microscopy ?
1674-1683 Leeuwenhoek created more powerful lenses and was the first to observe bacteria and protocists
What was dumortiers contribution to microscopy?
1832 First to observe cell division in plant cells, this provided evidence against spontaneous cellular duplication
What was Browns contribution to microscopy?
1833 First to describe the nucleus of a plant cell
What was Schlieden and Purkyněs contributions to microscopy?
1837-1838 Schlieden said all plant tissues were made up of cells - thinly sliced specimens were introduced. Purkyně said ‘basic cellular tissue is clearly analogous to that of plants’.
What was Remaks contribution to microscopy?
1844-(1855) Remak was the first to observe cell division in animal cells. Virchow published these cells as his own.
What was Pasteur contribution to microscopy?
Pasteur disproved the theory of spontaneous generation. Bacteria would only grow in a sterile nutrient broth after it had been exposed to air.
QUESTIONS:
1)Outline the importance of microscopes in the study of living organisms
2) Suggest why, with reasons, why cell theory was not fully developed before the mid 19th century.
What is an electron micrograph?
Photograph of an image seen using an electron microscope.
What is magnification?
The number of times larger an object appears, compared with the size of the object.
What are organelles?
Small structures within cells, each of which has a specific function.
What is a photo micrograph?
Photograph of an image seen using an optical microscope.
What is resolution?
The clarity of an image; the higher the resolution, the clearer the image.
What are the 4 different kinds of microscopes?
Light microscope, Laser scanning confocal microscope, Transmission electron microscopes and Scanning electron microscopes.
What are the features of a light microscope?
Source of light: Bulb
Lens: Glass
Magnification: x1500-x2000
Resolution: 200
Description of specimen: Alive, dead or stained
Need for fixing/staining: Unless dead, yes optical stains used
Cost: ~£350
What are the features of a laser scanning confocal microscope?
Light source: Laser
Lens: Glass-special dichroic mirror required
Magnification: x1000+
Resolution(nm): 200
Description of specimen: Can use live or dead cells. Often require sectioning.
Need for fixing/staining: Unless alive, yes. Fluorescent dyes used.
Cost: Costly, several £1000s
What are the features of a transmission electron microscope?
Light source: High voltage electron beam
Lens: Electromagnet
Magnification: x500,000
Resolution(nm): 0.5-0.2 1(typical of older TEM)
Description of specimen: Dead. Extremely thin sections.
Need for fixing/staining: Yes. Electrodense stains used.
Cost: Very expensive. Running costs and technician.
What are the features of a scanning electron microscope?
Light source: High voltage electron beam
Bulb: Electromagnet
Magnification: x250000
Resolution(nm): 0.5 2-5(typical of older SEM)
Description of specimen: Dead. Can section and freeze fracture.
Need for fixing/staining: Fixation, yes. Specimen coated in metal (gold or platinum)
Cost: Very expensive. Running costs and and technician.
What is the resolution equation?
R= 1/2wavelength
What is the magnification equation?
Magnification= Image size / object size
