TEST 2 Notes bio1202

TEST 2 Notes bio1202 - C hapter 27 Prokaryotes One thing...

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Chapter 27: Prokaryotes One thing that E. coli and other bacteria have in common with eukaryotes is the presence of ribosomes. Concept 27.1: Structural and functional adaptations contribute to prokaryotic success o Prokaryotes are unicellular Some colonial forms o Range in size from 1-5 micrometers Thiomargarita namibiensis (750 micrometers) o No membrane-bound organelles o Circular chromosomes o Prokaryotic cells have a variety of shapes The 3 most common are spheres (cocci), rods (bacilli), and spirals (spirilli) o Cell-surface structures Cell wall Maintains cell shape, provides physical protection, prevents cell from bursting in a hypotonic environment Composed of peptidoglycan in bacteria May also have an outer phospholipid membrane A capsule (a sticky layer of polysaccharide or protein) may cover the cell wall of many prokaryotes Fimbriae and pilli allow prokaryotes to stick to their substrate or other individuals in a colony Gram-negative bacteria have less peptidoglycan than gram-positive cells and their cell walls are more complex structurally. o Motility
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Motile bacteria move by means of flagellae Structurally different from eukaryotic flagella In a heterozygous environment, bacteria exhibit taxis (ability to move toward or away from certain stimuli) E.g., positive chemotaxis-moving toward a chemical stimulus o Internal organization Prokaryotes do not have membrane-bound organelles Some do have specialized membranes that perform metabolic functions o Genomic organization Prokaryotic chromosome (circular DNA found in the nucleoid region) Not within a nucleus Plasmid (smaller circular DNA rings) Additional genes not always necessary for basic survival E.g., antibiotic resistance o Reproduction Prokaryotes reproduce quickly by binary fission Can divide every 1-3 hours Form of asexual reproduction Produces genetically identical daughter cells Concept 27.2: Rapid reproduction, mutation, and genetic recombination promote genetic diversity in prokaryotes. o Bacteria reproduce asexually leading to genetically identical daughter cells
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Rapid reproduction leads to large populations and high mutation rates High genetic diversity and rapid evolutionary rates o Genetic exchange Bacterial conjugation Transfer of genetic material between 2 bacteria Not necessarily the same species (horizontal gene transfer) Plasmids are usually transmitted from donor through a sex pilus o Transformation Uptake of foreign DNA from the environment Transduction Viruses carry bacterial DNA from one host cell to another Groups of staphylococci look like clusters of grapes. Concept 27.2: diverse nutritional and metabolic adaptations have evolved
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This note was uploaded on 03/31/2010 for the course BIOL 1202 taught by Professor Gregg during the Spring '08 term at LSU.

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TEST 2 Notes bio1202 - C hapter 27 Prokaryotes One thing...

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