BSCI Lecture 9 Cell Structure

BSCI Lecture 9 Cell Structure - Overview: The Fundamental...

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Overview: The Fundamental Units of Life All organisms are made of cells The cell is the simplest collection of matter that can live Cell structure is correlated to cellular function All cells are related by their descent from earlier cells
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To study cells, biologists use microscopes and the tools of biochemistry Though usually too small to be seen by the unaided eye, cells can be complex
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Microscopy Scientists use microscopes to visualize cells too small to see with the naked eye In a light microscope (LM) , visible light passes through a specimen and then through glass lenses, which magnify the image
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The quality of an image depends on Magnification , the ratio of an object’s image size to its real size Resolution , the measure of the clarity of the image, or the minimum distance of two distinguishable points Contrast , visible differences in parts of the sample
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Fig. 6-2 10 m 1 m 0.1 m 1 cm 1 mm 100 µm 10 µm 1 µm 100 nm 10 nm 1 nm 0.1 nm Atoms Small molecules Lipids Proteins Ribosomes Viruses Smallest bacteria Mitochondrion Nucleus Most bacteria Most plant and animal cells Frog egg Chicken egg Length of some nerve and muscle cells Human height Unaided eye Light microscope Electron microscope
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LMs can magnify effectively to about 1,000 times the size of the actual specimen Various techniques enhance contrast and enable cell components to be stained or labeled Most subcellular structures, including organelles (membrane-enclosed compartments), are too small to be resolved by an LM
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Brightfield (unstained specimen) Brightfield (stained specimen) 50 μ m Confocal Differential-interference- contrast (Nomarski) Fluorescence 10 μ m Deconvolution Super-resolution Scanning electron microscopy (SEM) Transmission electron microscopy (TEM) Cross section of cilium Longitudinal section of cilium Cilia Electron Microscopy (EM) 1 10 2 μ m 2 μ m Light Microscopy (LM) Phase-contrast Figure 6.3
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Two basic types of electron microscopes (EMs) are used to study subcellular structures
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BSCI Lecture 9 Cell Structure - Overview: The Fundamental...

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