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Viruses
Non-Living
What is a
V i r u s?
• A disease causing particle consisting
of hereditary material enclosed in a
protein coat that is smaller and less
complex than a cell
What is a Virus?
A virus infects a host.
A host is a living thing that
provides a home and food for
a parasite.
A parasite is an organism that
survives by living on or in a
host organism, thus harming
it.
What does a virus look like?
Figure 19-9 Virus Structures
Viral Structures and Names
Tobacco Mosaic
Virus
T4 Bacteriophage
Head
Influenza
Virus
RNA
DNA
Capsid
proteins
Capsid
RNA
Tail
sheath
Tail
fiber
Surface
proteins
The really small guys.
Membrane
envelope
How does a virus
reproduce?
1. Attaches to a cell.
2. Injects hereditary material into the
cell.
3. Uses cell to perform life functions.
(for the virus)
4. Virus replicates using the cell.
5. The cell ruptures, releasing multiple
copies of the virus.
6. The cell dies.
Life Cycles
What are some examples of a
virus?
Colds, fever blisters, and warts.
AIDS, measles, influenza, hepatitis,
small pox, polio, mumps, encephalitis,
herpes.
Papilloma virus Warts
Influenze virus Flu
Human
Immunodeficiency
Virus - AIDS
Rabies Virus
Viral Diseases
Type of Virus
Nucleic Acid
Disease
Oncogenic viruses
DNA
Cancer
Retrovirus
RNA
Cancer, AIDS
Adenoviruses
DNA
Respiratory infections
Herpesviruses
DNA
Chickenpox
Poxviruses
DNA
Smallpox
Some viruses can be prevented with vaccines. Antibiotics
do not work on viruses. Why not?
What defines life?
• Must meet ALL of H.O.G.R.E.C.R.
– Homeostasis
– Organization (atoms to organism)
– Growth & development
– Reproduction
– Energy use/metabolism
– Cell(s)
– Respond to stimulus
Viruses are not Cells
•
•
•
•
•
•
Viruses have nucleic acids
Viruses have a protein coat
Viruses cannot grow
Viruses do not use energy
Viruses do not meet all of H.O.G.R.E.C.R.
Viruses can change over time using
energy from host cells
Bacteria
Structure of a Bacterium
Ribosome
Peptidoglycan
Cell
Cell
wall membrane
Flagellum
DNA
Pili
Bacteria are prokaryotes. (Cell is prokaryotic)
“Little bit larger now” but still microscopic.
Bacterial Diseases and Prevention
Disease
Pathogen
Prevention
Tooth decay
Streptococcus mutans
Regular dental hygiene
Lyme disease
Borrelia burgdorferi
Protection from tick bites
Tetanus
Clostridium tetani
Current tetanus vaccination
Tuberculosis
Mycobacterium tuberculosis
Vaccination
Salmonella food poisoning
Salmonella enteritidis
Proper food-handling practices
Pneumonia
Streptococcus pneumoniae
Maintaining good health
Cholera
Vibrio cholerae
Clean water supplies
Proper hygiene can prevent many bacterial
infections. Antibiotics treat most bacterial
diseases.