Virus
• Contain DNA and a protein coat
• Reproduce by invading a living host cell
• Viruses are the ultimate parasite
• Viruses not made up of cells.
• Cannot live on their own.
Are Viruses Living or
Non-living?
• Viruses are both and neither
• They have some properties of life
but not others
• For example, viruses can be killed,
even crystallized like table salt
• However, they can’t maintain a
constant internal state
(homeostasis).
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What are Viruses?
• A virus is a non-
cellular particle
made up of
genetic material
and protein that
can invade living
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Smallpox
•Deadly viruses are
said to be virulent
•Smallpox has been
eradicated in the
world today
•Edward Jenner (1796)
developed a smallpox
vaccine using milder
cowpox viruses
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Viewing Viruses
•Viruses are smaller
than the smallest cell
•Measured in
nanometers
•Viruses couldn’t be
seen until the
electron microscope
was invented in the
20th century
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Size of Viruses
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Characteristics
• Non living structures
• Noncellular
• Contain a protein coat called the
capsid
• Have a nucleic acid core containing
DNA or RNA
• Capable of reproducing only when
inside a HOST cell
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Characteristics
• Some viruses are enclosed CAPSID
in an protective envelope
DNA
• Some viruses may have
spikes to help attach to
the host cell
• Most viruses infect only
SPECIFIC host cells
ENVELOPE SPIKES
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Characteristics
•Individual
subunits are
called capsomeres
•Viral capsids
(coats) are made
of individual
protein subunits CAPSOMERES
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Characteristics
•Outside of host cells,
viruses are inactive
•Lack ribosomes and
enzymes needed for EBOLA VIRUS
metabolism
•Use the raw materials
and enzymes of the
host cell to be able to
reproduce HIV VIRUS
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Characteristics
•Some viruses may cause
some cancers like leukemia
•Virus-free cells are rare
•Some viruses cause
disease
•Smallpox, measles,
mononucleosis, influenza,
colds, warts, AIDS, Ebola
MEASLES
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Viral Shapes
•Viruses come in a variety of
shapes
•Some may be helical shape like
the Ebola virus
•Some may be polyhedral
shapes like the influenza virus
•Others have more complex
shapes like bacteriophages
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Helical Viruses
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Polyhedral Viruses
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Bacteriophage
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Herpes Virus
SIMPLEX I and II
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Adenovirus
COMMON COLD
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Influenza Virus
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Chickenpox Virus
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Papillomavirus –
Warts!
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Retroviruses
•HIV, the AIDS
virus, is a
retrovirus
•Feline Leukemia
Virus is also a
retrovirus
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Bacteria
•Prokaryotic
•Unicellular
•Reproduce asexually by Binary
Fission.
•Vital to the living world
•Decomposers- break down dead
material.
Endosymbiotic Theory
• Endosymbiosis refers to one species
living within another(the host)
• Movement of smaller photosynthetic
& heterotrophic prokaryotes into
larger prokaryotic host cells
• Formed cell organelles
chloroplast
mitochondria
Prokaryotic &
Eukaryotic Cells
Earliest
Prokaryotes
• Most numerous
organisms on Earth
• Include all bacteria
• Earliest fossils date
2.5 billion years old
Domains
Archaebacteria:
Found in harsh
environments
Undersea volcanic vents,
acidic hot springs, salty
water
Archaebacteria
Eubacteria
Bacterial
Structure
• Microscopic prokaryotes
• No nucleus or membrane-
bound organelles
• Contain ribosomes
• Single, circular chromosome
in nucleoid region
Bacterial Cell
Bacterial
Structure
PLASMIDS
•Have small rings of
DNA called Plasmids
•Unicellular
•Small in size (0.5 to
2μm)
Bacterial Structure
•Most grow best at pH
of 6.5 to 7.0
•Many act as
decomposers
recycling nutrients
•Some cause disease
Staphylococcus
Bacterial
Useful Bacteria
• Some
bacteria
can
degrade oil
• Used to
clean up oil
spills
Useful Bacteria
•Other uses
for bacteria
include
making
yogurt,
cheese, and
buttermilk.
Shapes Are Used
to Classify
• Bacillus: Rod shaped
• Coccus: Spherical
(round)
• Spirillum: Spiral
shape
Streptococcus Causes
Strep Throat
Bacillus - E. coli
Reproduction
• Bacteria reproduce asexually by
binary fission
• Single chromosome replicates & then
cell divides
• Rapid
• All new cells identical (clones)
Cellular organism copies it’s genetic information
then splits into two identical daughter cells
Reproduction
• Bacteria reproduce sexually by
Conjugation
• Form a tube between 2 bacteria
to exchange genetic material
• Held together by pili
• New cells NOT identical
Conjugation
Pathogens
• Called germs or microbes
• Cause disease
• May produce poisons or toxins
• Endotoxins released after
bacteria die (E. coli)
• Exotoxins released by Gram +
bacteria (C. tetani)
Diseases
• Pathogens are disease causing agents
• Bacteria harm by producing toxins that disrupt
body functions.
• Virus destroy the cell it infects
• Vaccine- a weakened pathogen that prompts the
body to form immunity to the disease.
• Antibiotics kill bacteria
• A healthy immune system is the only defense
against virus.
Infectious Disease
• A disease is any change, other than an injury,
that disrupts the normal functions of the body.
• Some are produced by agents, such as bacteria,
viruses, and fungi.
• Others are caused by materials in the
environment, such as cigarette smoke.
• Some diseases are inherited.
• Diseases caused by pathogens are called
infectious diseases.
How Diseases Are Spread
• Coughing, sneezing, or physical contact
• Through the air (“airborne”)
• Contaminated water or food
• Infected animals
• Animals that carry pathogens from person
to person are called vectors.
Fighting Infectious Diseases
• Antibiotics kill bacteria.
• Over the counter drugs treat only the
symptoms of a disease.
• Best treatment includes rest, a well-
balanced diet, and plenty of fluids.
The Immune System
• Function of this system is to fight infection
through the production of cells that
inactivate foreign substances or cells.
Called immunity.
• Categories of defense include nonspecific
and specific defenses.
Nonspecific Defenses: 1st Line of
Defense
• Function is to keep pathogens out of the
body.
• Ex. Skin, mucus, sweat, and tears
• Most important nonspecific defense is the
skin
• Symptoms of an infection is swelling,
redness, and pain near the site.
Second Line of Defense: The Inflammatory
Response
• A reaction to tissue damage caused by injury or infection.
• Reaction includes the over production of white blood cells (phagocytes) and vessel
expansion near the wound.
• A fever may spike narrowing the temperature range of survival for the bacteria.
B and T Cells
• B cells –White blood cells that make
antibodies that attack pathogens in the
blood
• T cells- white blood cells that find and
destroy abnormal or infected cells.
Acquired Immunity
Active Immunity: antibodies are made
from the body’s reaction to a vaccine, a
weakened or mild form of the pathogen.
Passive Immunity: when antibodies
produced from another animal are
injected into one that has not been
exposed; short time of protection; ex.
mother to baby; passive immunization
Disorders of the Immune System
Allergies: allergens initiate antigen
production; antigens initiate an
inflammatory response; Histamines are
released increasing blood flow and
mucus production; Antihistamines
counteract the effects of histamines;
asthma narrows the respiratory air
passages
Disorders
Autoimmune Diseases: your immune
system attacks the body’s own cells; ex.
Rheumatoid arthritis, MS, Lupus, Type I
diabetes
Immunodeficiency Disease: immune system
fails to develop normally; AIDS
AIDS destroys T cells
AIDS is caused by HIV
The Environment and Your Health
Water Quality: providing safe drinking water has
probably been the single most important factor
in nearly doubling human life expectancy
Bioterrorism
Cancer: mutagens ie UV light, radon,chemicals
Air Quality: carbon monoxide, ozone, and
airborne particulates such as lead and
asbestos
Nitrogen Cycle
• Organisms use nitrogen to build proteins
• Bacteria breaks down dead organisms to release
the nitrogen.
• Bacteria fixes the nitrogen so plants can take it
up.
• Plants take up the nitrogen by their roots
• Plants use the nitrogen to make proteins.
• Consumers eat the plants –producers- to get the
nitrogen.
Assignment
• Workbook Pages 29,168-173, 177-178,182
& 183
• Virus
• Prokaryote
• Vaccine
• Bacteria
• Binary fission
• Nitrogen cycle