Latin = Poison A tiny disease-causing agent consisting of a
core of nucleic acid, usually encased in protein. Not cellular
Cannot move about on own Cannot carry on metabolic activities
independently Pathogen a disease causing agent
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Consist of a core of nucleic acid Contain either DNA or RNA
(not both) Surrounded by a protein coat Lack Ribosomes and enzymes
necessary for protein production
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Classified according to common characteristics Type of nucleic
acid Presence or absence of a protein coat Does not use Linnaean
system
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Escaped Gene Hypothesis Viruses were originally fragments of
DNA or RNA that escaped from cellular organisms Some viruses may
trace their origins to animal cells, plant cells, or bacterial
cells May explain why each virus usually infect only certain
related species
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Viruses that attack/kill bacteria AKA Bacteria Eaters or phages
Complex virus Used to be used in place of antibiotics and sulfa
drugs They are making a comeback because of bacterial resistance to
antibiotics Used to attach to bacteria
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Lytic Cycle vs. Lysogenic Cycle
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The life cycle of a virus that kills the host cell by lysing
(destroying) it Forces host cell to replicate viral particles by
using its metabolic machinery 1. The virus attaches to receptors on
the host cell wall 2. Nucleic acid of virus moves through plasma
membrane and into the cytoplasm of the host cell 3. The protein
coat remains on the outside exterior of the host cell 4. The virus
uses the cells metabolic machinery to make new bacteriophage
viruses 5. Bacterial cell lyses and releases many phages to infect
other cells 6. Results in the death of the host cell
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The life cycle of a virus that kills the host cell by lysing
(destroying) it Forces host cell to replicate viral particles by
using its metabolic machinery
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1. The virus attaches to receptors on the host cell wall 2.
Nucleic acid of virus moves through plasma membrane and into the
cytoplasm of the host cell 3. The protein coat remains on the
outside exterior of the host cell 4. The virus uses the cells
metabolic machinery to make new bacteriophage viruses 5. Bacterial
cell lyses and releases many phages to infect other cells 6.
Results in the death of the host cell Fig. 19-2, p. 367
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Describe the Lytic Cycle. What organisms does it occur in?
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Integrate their DNA into the host bacteria cells DNA Does not
destroy its host Prophage when viral nucleic acid is integrated
with bacterial DNA When bacterial DNA replicates, viral prophage
replicates Bacterial cells carrying prophages are called lysogenic
cells Can spontaneously turn to lytic
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Fig. 19-3, p. 368 Lysogenic Cycle
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NOYES Not cellular A cell is the basic unit of life By itself,
a virus can do nothing It cannot metabolize It cannot reproduce
Does not have the metabolic machinery nor cellular structures to do
so Once in the presence of a living cell a virus behaves as if it
were alive It reproduces by taking over the metabolic machinery of
the host cell Uses the cells enzymes, ribosomes, and other
components
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Are viruses alive?
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Viroid: Small & Circular in shape Infectious molecule of
RNA Causes many plant diseases Prion An infectious agent Composed
only of protein
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Cellular organisms 2 Domains Bacteria & Archea 3 main
shapes Cocci Spherical Groups of 2 Diplococci Long Chains
Streptococci Irregular grape-like clumps staphylococci Bacilli Rod
Shaped Spirilla Helix Shaped
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Fig. 19-5a, p. 370
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Fig. 19-5b, p. 370
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Fig. 19-5c, p. 370
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Prokaryotic cell structure is simpler than eukaryotic cell
structure Lack membrane-bound organelles No nuclei No mitochondria
No chloroplasts No endoplasmic reticulum No Golgi apparatus Mostly
Unicellular Small is size (typically 1/1000 the size of a
Eukaryotic cell) Usually have a cell wall
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Fig. 19-6, p. 371
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Prokaryotes are heterotrophs Hetero = other Tropho =
nourishment Must obtain organic molecules from other organism Most
are decomposers They get their nourishment from dead organic matter
Or they live in or on other organisms Commensals neither help nor
harm their hosts Parasites live at the expense of their host and
can cause disease Mutualistic both organisms benefit from the
association
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What is the difference between parasitic, commensal, and
mutualistic prokaryotes?
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Some prokaryotes are Autotrophs Auto = self tropho =
nourishment Manufacture their own organic molecules from carbon
dioxide Photosynthetic prokaryotes Obtain energy from light
Chemiosynthetic prokaryotes - Obtain energy from chemical
reactions
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Most Prokaryotes are Aerobes They require atmospheric oxygen
for cellular respiration Some are Faculative Anaerobes They use
oxygen for cellular respiration if available, but will respire
anaerobically when oxygen is absent Some are Obligate Anaerobes
Carry on cellular respiration only in the absence of oxygen
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Binary Fission One cell divides into two similar cells
Conjugation Two cells of different physiological mating types come
together, and genetic material is transferred through pilli from
one cell (donor) to the other (recipient)
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Recipient cell Conjugation pilus Donor cell Fig. 19-10, p.
373
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Biofilms are microbial communities that consist of many species
of prokaryotes In watery environments, unicellular organisms
secrete a slimy, glue-like substance rich in polysaccharides They
embed themselves in it. Ex. Dental Plaque
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ARCHAEABACTERIA Absence of peptidoglycan in cell wall Most live
in harsh environments Present almost universally Abundant in air,
soil, water Abundant in bodies of organisms FEW PLACES ON EARTH ARE
COMPLETELY DEVOID OF BACTERIA
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3 Main Types Methanogens (methane producers) Obligated
anaerobes that produce methane gas from simple carbon compounds
Live in sewage and swamp sediments Common in digestive tracts of
humans and other animals Halophiles Live in very salty environments
Use aerobic respiration to make ATP Carry out a form of
photosynthesis using purple pigment Thermophiles Grow in hot and
acidic environments Found in hot springs and volcanic areas under
the sea
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Wall-less Bacteria Mycoplasmas A tiny bacterium bounded by a
plasma membrane but lacking a typical bacterial cell wall Live in
soil, sewage, or are parasitic on plants or animals Gram-Negative
Bacteria that does not retain Gram stain/do not have peptidoglycan
Gram-Positive Bacteria that do retain Gram stain/contain
peptidoglycan