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Cells are the basic unit of life.
Detailed study of the cell began in the 1830s
some of the scientists contributing to the understanding of cell structure and function were Robert Brown, Matthais Schleiden, Theodor Schwann, and Rudolph Virchow.
The cell theory states that all organisms are composed of cells, that cells are basic units of structure and function in organisms, and that cells come only from preexisting cells because cells are self-reproducing.
A. Cell Size
Cells range in size from one millimeter down to one micrometer.
Cells need a surface area of plasma membrane large enough to adequately exchange materials.
The surface area to volume ratio requires that cells be small.
As cells get larger in volume, surface area relative to volume decreases.
Size limits how large the actively metabolizing cells can become.
Cells needing greater surface area utilize membrane modifications such as folding, microvilli, etc.
B. Microscopy Today (Nature of Science reading)
Types of microscopes
Compound light microscopes use light rays focused by glass lenses.
Transmission electron microscopes (TEM) use electrons passing through specimen and focused by electromagnetic lenses.
Scanning electron microscopes (SEM) use electrons scanned across metal-coated specimen; secondary electrons given off by metal are collected by a detector.
Magnification is a function of wavelength; the shorter wavelengths of electrons allow greater magnification than the longer wavelengths of light rays.
Resolution is the minimum distance between two objects at which they can still be seen as separate objects.
Contrast is the difference in the shading of an object compared to its background.
Phase contrast and differential interface contrast microscopy uses fluorescent antibodies to reveal proteins in cells.
Confocal microscopy uses laser beam to focus on a shallow plane within the cell; this forms a series of optical sections from which a computer creates a three dimensional image.
Video-enhanced contrast microscopy accentuates the light and dark regions and may use a computer to contrast regions with false colors.
Bright-field, phase contrast, differential interference, and darkfield are different types of light microscopes.
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