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a. All organisms are made of __.
b. All cells are related by their __
c. Development of __-->advance of science
i. Study of cells progressed with invention of __
1. Robert Hook (1665)
a. __
2. Antoni van Leeuwenhoek
__
cells, which are the simplest collection of matter that can be alive
descent, but have been modified
instruments
microscopes in 1590
Cell walls
visualized living cells
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Explain light microscopes.
Visible liht is passed throuh the specimen and then through glass lenses, which refract the light in ways that allow image of specimen to be magnified
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Threee important parameters of microscopes.
- a.
- Magnification: ratio of an object’s
- size to its real size
- b.
- Resolution: measure of the clarity
- of the image; minimum distance two points can be separated and still be
- distinguished as two points
- c.
- Contrast: accentuates differences
- in parts of the sample
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__ are the membrane enclosed structures within eukaryotic cells. Seeing them required the electron microscope
organelles
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EM
- 1. Focuses beam of electrons through or on specimen surface
- a. Resolution is inversely related to the wavelength of the radiation a microscope uses for iimaging, and electron beans are shorter wavelengths than visible light
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SEM
- a. Detailed study of the topography of a specimen
- i. Scans surface coated with film of gold, exciting electrons on the surface, and detecting and translating patter
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Transmission Electron Microscope
- a. Studies internal structures
- i. Aims through thin section, which has been stained with atoms of heavy metals
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Advantages and Disadvantages
- 1. Disadvantage of EM:
- a. Methods used to prepare specimen kills cells
- 2. Advantage of LM:
- a. Labeling molecules or structures with fluorescent markers made it possible to see structures with increasing detail and revealed sharpened images of 3D tissues and cells
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__, the study of cell structure, relies on microscopes.
___,
the study of the chemical processes of cells, was integrated.
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Cell Fractionation
- i. Takes cells apart and separates major organells and other subcellular structures from one another using a centrifuge
- 1. Spins test tubes holding mixtures of disrupted cells at different speeds, causing a fraction of the cell components to settle on the bottom onf the tube
- a. Lower speeds= larger components
- b. Higher speeds= smaller component
- ii. Allows identification of functions
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Explain electron microscopy.
SEM: 3D surface of the topography of a specimen (surface)
TEM: profiles a thin section of a specimen, revealing internal structure
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