Chapter 6

Chapter 6 - light microscope(LM visible light passed...

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light microscope (LM)- visible light passed through specimen and then through glass lenses electron microscope (EM)- focuses a beam of electrons through the specimen or onto its surface o scanning electron microscope (SEM)- beam scans the surface, which is coated with a thin film of gold, excites electrons on the surface, device translates pattern of electrons, great depth of field (3D image) o transmission electron microscope (TEM)- beam through a very thin section, specimen stained with heavy metals, electrons scattered more in denser images, displayed pattern of transmitted electrons, electromagnets as lenses. disadvantage: kills the cell magnification- ration of image size to real size resolution- measure of clarity contrast- accentuates differences in parts of the sample (most of the improvements in LM are in contrast) cell fractionation- separates the major organelles via centrifuge, forms a pellet at the end, enables researchers to prepare specific cell components in bulk and identify their functions common cellular features o plasma membrane- selective barrier binding the cell o cytosol- semifluid, jellylike substance in which organelles, etc are found o chromosomes- carry genes in the form of DNA o ribosomes- complexes that make proteins according to instructions from genes Prokaryotes Eukaryotes Nucleoid region in which DNA is concentrated Interior: cytoplasm Nucleus- bound by a double membrane Interior: cytoplasm in between the nucleus and membrane organelles eukaryotic cells are generally much larger (structure relates to function)
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plasma membrane functions as a selective barrier that allows passage of oxygen, nutrients, and wastes to the entire cell ratio of surface area to volume, if a cell increases in size the ratio of volume to surface area decreases larger organisms have more cells, not larger cells some cells have microvilli to increase the surface area (thin long projections) Animal Cell Planet Cell lysosomes- digestive organelle where macromolecules are hydrolyzed centrosomes, with centrioles- region where microtubules are initiated, contains a pair of centrioles flagella- locomotion, composed of a cluster of microtubules, extension of plasma membrane chloroplasts- conversion of light energy to chemical energy stored in sugar molecules central vacuole- storage, breakdown of waste, hydrolysis of macromolecules, enlargement of vacuole is major mechanism of plant growth cell wall- maintains cell shape, made of cellulose, polysacc, and protein plasmodesmata- channels through cell walls connecting adjacent cells Nucleus o Contains most of the genes in the eukaryotic cell o Nuclear envelope: encloses the nucleus, double membrane (each membrane is a lipid bilayer with associated proteins, separated by a space of 20-40 nm) Perforated by pore structures that are about 1—nm in diameter, at the lip of each pore, inner and outer membranes are continuous
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Chapter 6 - light microscope(LM visible light passed...

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