Transcript Section 19-3 - Effingham County Schools

Viruses
Viruses are not a
type of bacteria!
Virus comes from
the Latin word for
poison.
Viruses are so small
they can only be
seen with Electron
Microscope.
Bacteria and other
cells are large
enough to be seen
with a light
microscope.
Not considered to be a living thing because
they are non-cellular particle. They are
only made up of genetic material (DNA or
RNA) and a protein coat.
Parasites! CANNOT carry out life processes
unless within a host (living cell). Usually
host specific- infect only one type of host.
Figure 19-13 Virus Structures
Viruses infect a variety of different organisms and come
Section 19-3
in many
different shapes
Tobacco Mosaic
Virus
T4 Bacteriophage
Protein
Influenza
Virus
RNA
DNA
RNA
Protein
Protein
Tail
Tail
fiber
Surface
proteins
Infects: plants
Infects: bacteria
Go to
Section:
Envelope
Infects: Animals
Viral Diseases
Mostly caused by virus destroying cells in
body.
Cause human diseases such as polio,
measles, AIDS, and the common cold
Viruses are generally destructive.
Virus has to be inside a living cell to
reproduce. The cell that it reproduces in
is a host cell. A virus destroys its host
cell.
Lytic Cycle -how a virus reproduces
When a virus enters a cell and is
active it causes the cell to make
new viruses. This will eventually
destroy the host cell.
Steps of Lytic Cycle
1. Attach-virus attaches to the surface of a cell
2. Inject- the hereditary material of the virus
injects itself into the cell.
3. Copy-the viral DNA takes control of the cell
and the cell begins to make new virus particles.
4. Assembles- viral particle are assembled into
new viruses
5. Release-the cell bursts open and hundreds of
new virus particles are released. These new
virus particles go on to infect other cells.
Figure 19-14 The Lytic Cycle
Attach
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Bacteriophage
Release
DNA
Bacterial
DNA
Lytic Cycle
Inject
Assemble
Bacteriophage
Copy
Go to
Section:
Bacteriophage DNA
Bacteriophage protein
Latent Viruses- (Dormant Virus) Do not
immediately enter the lytic cycle. The viral
DNA becomes part of the cell’s DNA without
immediately destroying the cell or making
new viruses. A latent virus can exist inside
host cells for many years. Can become active
at any time. Ex- Cold sores.
Viral Diseases
CANNOT be treated with antibiotics
Best Protection is prevention - Prevented
by safe practices or Vaccine if available.
(Vaccines must be used before infection
begins)
Franklin D
Roosevelt
Rabies
SARS- flu-like virus that leads to severe pneumonia
Ebola virus- liquification of internal
organs and severe bleed out
III. Kinds of Viruses
A. Viruses are classified by their shape, the kind
of hereditary material they contain, organism
that they infect and reproduction.
B. The protein that covers a virus gives it its
shape.
C. Viruses are often named for the disease that
they cause (Polio) or the organ or tissue that
they infect (SARS).
VII. Steps of Lysogenic cycle
1. Virus attaches to the cell and injects
hereditary material into the cell.
2. Virus becomes part of the cell’s DNA.
3. Cell divides, creating viral DNA along
with its own DNA.
4. This can happen for years until virus
becomes active
5. Then it will enter the lytic cycle
Figure 19-15 A Lysogenic Infection
Section 19-3
a) Virus attaches and invades
Bacterial
chromosome
Bacteriophage
DNA
c) Viral DNA separates from
Cell’s DNA and becomes active
c) Cell divides
Lytic
Cycle
e) Cell breaks open and
Releases virus
Prophage
d) New viruses are made
Go to
Section:
Lysogenic
Cycle
b) Virus’ DNA becomes
Part of Cell’s DNA
Bovine Spongiform
Encephalopathy
Mad Cow Disease
VIII. Prions- no genetic material (DNA nor
RNA) only protein which infects the
nervous tissue of the brain (scientists
think they cause Mad Cow Disease).
Finding the host: Outbreak!