Test_Cell - To Study Cells Scientists use Microscopes and...

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To Study Cells Scientists use Microscopes and the Tools of Biochemistry: Light Microscope – Visible light passed thru the specimen & glass lenses - Lens refract light such that the image of the specimen is magnified as it is projected to the eye - Magnification = Ratio of object’s image size to real size *Lens system * Magnify to 1000x the size of the specimen - Resolution = Measure of clarity of image; minimum distance 2 points can be separated *Can’t resolve details finer than 0.2 micrometers (200 nm) *Cannot resolve objects that are less than ½ the wavelength of the incident light (light illuminating the object) ^Wavelength of incident light: 400 nm – 700 nm ^LM: 200 nm – 350nm; .2 um - .35 um - Contrast= Accentuation of different parts of the sample *Stain material to make more visible (ex: hematoxalin, stains nucleus) *Differentiate between cells within a tissue and different tissues Techniques for light microscopes: - Brightfield (unstained): Passes light directly thru specimen; not much contrast - Brightfield (stained): Enhances contrast - Phase-Contrast: Enhances contrast in unstained cells by amplifying variations in density within specimen (useful for examining living cells) - Differential-Interference-Contrast (Nomarski): Exaggerates difference in densities - Fluorescence: Shows the location of specific molecules in the cell by tagging the molecules with fluorescence dyes or antibodies *Absorb ultraviolent radiation & emit visible light - Confocal: Fluorescence in layers Electron Microscope – Focuses a beam of electrons through the specimen or onto its surface - Electron beams have much shorter wavelengths than visible light - Cell ultrastructure = cellular anatomy revealed by an electron microscope Scanning Electron Microscope – Electron beam scans the surface of the sample - Results in a 3D image Transmission Electron Microscope – Used to study the internal ultrastructure of cells - Aims an electron beam at a very thin section of the specimen A disadvantage of EM is that methods used to prepare the specimens kill the cells Max magnification in LM: 1500x, in EM: 50000x Cytology = study of cell structure Cell Fractionation – Takes cells apart and separates the major organelles and other subcellular structures from one another - Centrifuge used to separate - Enables researchers to prepare in bulk specific cell components and identify their function Freeze Fracture: Cell is frozen & fractured with a knife - Splits phospholipid bilayer into 2 layers Artefact: - Something incorrect caused by method/technique - Check my comparing with other people & using a different method
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Eukaryotic Cells have Internal Membranes that Compartmentalize their Function: Things all cells have in common: - Plasma membrane, cytosol, chromosomes, ribosomes Eukaryotic cells vs. Prokaryotic cells - E: stores DNA in nucleus (double membrane) - P: DNA in nucleoid (no membrane)
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Test_Cell - To Study Cells Scientists use Microscopes and...

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