Lecture 4 - Processes of Life Growth Reproduction...

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Processes of Life • Growth • Reproduction • Responsiveness • Metabolism
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Prokaryotic Cells: An Overview Prokaryotes – Do not have membrane surrounding their DNA; lack a nucleus – Lack various internal structures bound with phospholipid membranes – Are small, ~1.0 μm in diameter – Have a simple structure – Composed of bacteria and archaea
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Prokaryotic Cells: An Overview [INSERT FIGURE 3.2]
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External Structures of Prokaryotic Cells Glycocalyces – Gelatinous, sticky substance surrounding the outside of the cell – Composed of polysaccharides, polypeptides, or both
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External Structures of Prokaryotic Cells Two Types of Glycocalyces – Capsule • Composed of organized repeating units of organic chemicals • Firmly attached to cell surface • Protects cells from drying out • May prevent bacteria from being recognized and destroyed by host – Slime layer • Loosely attached to cell surface • Water soluble • Protects cells from drying out • Sticky layer that allows prokaryotes to attach to surfaces
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External Structures of Prokaryotic Cells [INSERT FIGURE 3.5]
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External Structures of Prokaryotic Cells Flagella – Are responsible for movement – Have long structures that extend beyond cell surface – Are not present on all prokaryotes
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External Structures of Prokaryotic Cells Flagella – Structure • Composed of filament, hook, and basal body • Flagellin protein (filament) deposited in a helix at the lengthening tip • Base of filament inserts into hook • Basal body anchors filament and hook to cell wall by a rod and a series of either two or four rings of integral proteins • Filament capable of rotating 360º
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External Structures of Prokaryotic Cells
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External Structures of Prokaryotic Cells Flagella – Function • Rotation propels bacterium through environment • Rotation reversible, can be clockwise or counterclockwise • Bacteria move in response to stimuli (taxis) – Runs – Tumbles
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External Structures of Prokaryotic Cells [INSERT FIGURE 3.9]
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External Structures of Prokaryotic Cells Fimbriae • Sticky, bristlelike projections • Used by bacteria to adhere to one another, to hosts, and to substances in environment • Shorter than flagella • May be hundreds per cell • Serve an important function in biofilms
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External Structures of Prokaryotic Cells [INSERT FIGURE 3.10]
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External Structures of Prokaryotic Cells Pili – Tubules composed of pilin – Also known as conjugation pili – Longer than fimbriae but shorter than flagella – Bacteria typically only have one or two per cell – Mediate the transfer of DNA from one cell to another (conjugation)
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External Structures of Prokaryotic Cells [INSERT FIGURE 3.11]
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Prokaryotic Cell Walls • Provide structure and shape and protect cell from osmotic forces • Assist some cells in attaching to other cells or in eluding antimicrobial drugs • Not present in animal cells, so can target cell wall of bacteria with antibiotics • Bacteria and archaea have different cell wall chemistry
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This note was uploaded on 05/24/2011 for the course BIO 119 taught by Professor Stevendroho during the Spring '11 term at Moraine Valley Community College.

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Lecture 4 - Processes of Life Growth Reproduction...

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