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(CH 27, CH 19) - Coggle Diagram
CH 27
Cell-Surface Structures
The cell wall maintains shape, protects the cell, and prevents it from bursting in a hypotonic environment
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Prokaryotes
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Most prokaryotic cells are 0.5–5 μm, much smaller
than the 10–100 μm of many eukaryotic cells
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They have a variety of shapes including spheres
(cocci), rods (bacilli), and spirals
Most are unicellular, but some species form
colonies
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Ecological Interactions
Symbiosis is an ecological relationship in which two species live in close contact: a larger host with a smaller symbiont
In mutualism, both symbiotic organisms benefit
In commensalism, one organism benefits while neither harming nor helping the other
In parasitism, an organism called a parasite
harms but does not usually kill its host
Motility
About half of all prokaryotes exhibit taxis, the ability
to move toward or away from a stimulus
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Genetic Recombination
Genetic recombination, the combining of DNA from
two sources, contributes to prokaryote diversity
DNA from different individuals can be combined by
transformation, transduction, or conjugation
Movement of genes between individual prokaryotes of different species is called horizontal gene transfer
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Bacteria
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Proteobacteria
Gram-negative bacteria including photoautotrophs,
chemoautotrophs, and heterotrophs
Archaea
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Extremophiles
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Extreme thermophiles have adaptations that make their DNA and proteins stable at high temperatures (even above 100°C)
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Reproduction
Prokaryotes reproduce quickly by binary fission and can divide every 1–3 hours under optimal conditions
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Conjugation and Plasmids
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In bacteria, the DNA transfer is always one way:
One cell donates the DNA and the other receives it
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Chemical Recycling
Prokaryotes play a major role in the recycling of chemical elements between the living and nonliving components of the environment
For example, some chemoheterotrophic prokaryotes are decomposers, they break down dead organisms and wastes and release carbon and other elements
Mutualistic Bacteria
Human intestines are home to about 500–1,000
species of bacteria
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Antibiotic Resistance
Discovery of new antibiotics has not kept pace with
the rate at which bacteria have evolved resistance
For every antibiotic now in use, at least one species
of bacteria has developed resistance to it
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Spirochetes
These bacteria are helical gram-negative heterotrophs that spiral through the environment by rotating internal filaments
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CH 19
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Capsids and Envelopes
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A capsid can have a variety of structures; associated viruses may be referred to as helical or icosahedral viruses
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Viral envelopes
(derived from membranes of host cells) surround the capsids of influenza viruses and many other viruses found in animals
Bacteriophages
also called phages, are viruses
that infect bacteria
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Virus
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A virus is a very small infectious particle consisting of nucleic acid enclosed in a protein coat and, in some cases, a membranous envelope
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Viral Envelopes
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Viral glycoproteins on the envelope bind to specific
receptor molecules on the surface of a host cell
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The Lytic Cycle
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The lytic cycle produces new phages and lyses (breaks open) the host’s cell wall, releasing the progeny viruses • A phage that reproduces only by the lytic cycle is called a virulent phage