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Unformatted text preview: General Biology Laboratory Notes Laboratory 1: Cell Structure A. Parts of A Microscope 1. Condenser located immediately below the stage; focuses the light on the specimen; determines the contrast & resolution of what is seen 2. Objective located above the stage; projects a real image of the specimen that acts as the object for the ocular lens 3. Eyepiece (Ocular) located above the objective; further magnifies the object & forms a large virtual image onto the retina of the eye B. Operating the Microscope 1. Always focus with the scanning lens , then switch to higher power if needed 2. With the high power objective in position, focus with the fine adjustment only 3. Never remove a slide from beneath the high power objective; switch back to a lower power first C. Magnification Magnification: Ocular Objective Total Magnification Diameter of field (in micrometers) 10X (scanning) 4X 40X 4,500 m 10X (low) 10X 100X 1,600 m 10X (high) 40X 400X 400 m- 2-D slice of 3- D reality sections are thinner than the width of a cell -The field diameters of different lens systems are inversely proportional to their magnifications. -If an object appears to be a small dot with the high power objective, it is approximately 1 m Fd L /Fd H = M H /M L Fd H = field diameter at higher power Fd L = field diameter at lower power M H = magnification of high power lens M L = magnification of low power lens D. Measurement-(mm) millimeter = 1/1,000 of meter = 10-3 meter - (m) micrometer = 1/1,000,000 of meter = 10-6 meter -(nm) nanometer = 1/1,000,000,000 of meter = 10-9 meter -(mm) millimeter = 1/1,000 of meter - (m) micrometer = 1/1,000 of millimeter-(nm) nanometer = 1/1,000 of micrometer E. Image Formation-The lens system both reverses & inverts the image F. Plant Cells a. Elodea : leaf cells- approximate cell length: 100 m- approximate cell width: 20 m-organelles seen: vacuole, mitochondria, chloroplast, nucleus (w/ nucleolus) b. Onion: epidermis- approximate cell length: 100 m- approximate cell width: 20 m-organelles seen: cell wall, nucleus, mitochondria -Bromphenol Blue used to stain cell -Janus green: stain specific for mitochondria; stains them blue G. Animal Cell a. Human epithelial cell (cheek cell)- approximate cell diameter: 75 m-organelles seen: plasma membrane, nucleus, mitochondria -Bromphenol Blue & Janus green used to stain cell b. Euglena, Single-celled Eukaryotic Organism- approximate cell length: 50 m- approximate cell width: 10 m-organelles seen: cell membrane, mitochondria, nucleus (w/ nucleolus), chloroplasts H. Bacteria: Single-celled Prokaryotic cells-close to the same size as mitochondria & chloroplasts Laboratory 2: Cell Division Mitosis the division of the cell nucleus resulting in 2 daughter nuclei, each with the same number of chromosomes as the parent nucleus; at the beginning, each chromosome has been duplicated, being composed of 2 sister chromatids Prophase chromosomes first appear as darkly stained areas & later as distinct entities generally...
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- Spring '11