Ch_6_Notes - Chapter 6 9/15 The Importance of Cells All...

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Chapter 6 9/15
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The Importance of Cells All organisms are made of cells. The cell is the simplest unit of life. Cell structure is correlated to cellular function. All cells are related by their descent from earlier cells. Fundamental themes in biology 1. Structure = Function 2. Cells respond to their environment
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Microscopy Discovery of microscope in 16 th century enabled us to study cells & their components Light microscope - visible light to magnify an image Passes light through a specimen & then through glass lenses Lenses refract (bend) light, magnifying the image
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e e Refraction Magnifies
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Magnification - ratio of an object’s image size to its real size Multiple objective lens (4x) times ocular lens (10x) = 40x Resolution - measure of the clarity of the image Minimum distance 2 points can be separated and still be distinguished as 2 points Shorter wavelength – better resolution Minimum resolution ~200 nanometers (nm) Light Microscopy
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Magnify effectively to ~1,000 times the size of the actual specimen Various techniques enhance contrast and enable cell components to be stained Most cellular organelles too small to be resolved Light Microscopy
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10 m 1 m Human height Length of some nerve and muscle cells Chicken egg 0.1 m 1 cm Frog egg 1 mm 100 µm Most plant & animal cells 10 µm Nucleus 1 µm Most bacteria Mitochondrion Smallest bacteria Viruses 100 nm 10 nm Ribosomes Proteins Lipids 1 nm Small molecules Atoms 0.1 nm Unaided eye Light microscope Electron microscope 1 micron – 1 μ m Animal/plant cells 10-100 μ m Bacterial cells 1-10 μ m
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Electron Microscopy Scanning electron microscopes (SEMs)- focus a beam of electrons onto the surface of a specimen Provides 3D image Transmission electron microscopes (TEMs)- focus a beam of electrons through a specimen Mainly to study the internal ultrastructure of cells Electrons shorter wavelength than visible light- better resolution (clarity) Resolution 2 nm
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SEM TEM
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Cell Fractionation Study particular organelle function or composition Lyses cell and separates the major organelles Centrifuge- spins test tubes of cell solutions at high speeds Force separates out organelles based on size & density
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Classifying Cells Prokaryotic & eukaryotic Kingdoms: Bacteria prokaryotes
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Prokaryotic & Eukaryotic Cells Basic features of all cells: Plasma membrane Cytosol- fluid inside cell Chromosomes- genetic info Ribosomes- make proteins Cytoplasm- interior of cell
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Prokaryotes vs Eukaryotes No nucleus Nucleus Cell wall No cell wall No membrane bound organelles Membrane bound Smaller Larger Simple Complex
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A typical rod-shaped bacterium A thin section through the bacterium Bacillus coagulans (TEM) 0.5 µm Pili Nucleoid Ribosomes Plasma membrane wall Capsule Flagella Bacterial chromosome Prokaryotic Cell
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Eukaryotic Cell Animal Flagellum Centrosome CYTOSKELETON Microfilaments Intermediate filaments Microtubules Peroxisome ENDOPLASMIC RETICULUM Rough Smooth
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Ch_6_Notes - Chapter 6 9/15 The Importance of Cells All...

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