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Viruses!
Viruses are microscopic
particles that
invade the cells of
plant, animals, fungi,
and bacteria.
Bacteriaphage
AIDS Virus
Comparison
of structures
of viruses
and animal
cells.
1. A virus is not a cell. A
typical virus is composed
of a core of genetic
material surrounded by a
protein coat. The protein
coat protects the virus and
enables it to invade its host
cell.
2. In many viruses, DNA is
the genetic material.
Other viruses have RNA.
3. Viruses are parasitic
and can reproduce only
inside the cells of their
host. This makes
viruses very different
from bacteria and
protists.
AIDS Virus
Virus: Living or Not?
There has been an ongoing debate among scientists as
to whether or not viruses are alive or not alive. Viruses
lack three essential features of living things:
1. They are not made of cells
2. They cannot make proteins by themselves
3. They cannot use energy
•Even though viruses can reproduce they
are only able to so when inside living cells.
because they cannot reproduce on their
own most scientists classify them as non living things.
Viral genetic material has room for only a few genes. Usually they
are only genes that code for the protein coat and for enzymes that
enable to virus to take over the cell.
Virus Reproduction
How Viruses Work Video
(2:25)
All viruses reproduce by taking over the reproductive
machinery of a cell.
Differences Between
Lytic
and
Lysogenic Cycles
In the Lytic
Cycle:
1. Viral DNA destroys Cell DNA, takes over cell
functions and destroys the cell.
2. The Virus replicates and produces progeny
phages.
3. There are symptoms of viral infection.
4. the
Virulant
viral infection
In
Lysogenic
Cycle: takes place.
1. Viral DNA merges with Cell DNA and does not
destroy the cell.
2. The Virus does not produce progeny.
3. There are no symptoms of viral infection.
4. Temperate viral replication takes place.
Virus Reproduction
The reason HIV is such a dangerous virus is
because it has the ability to take over the white
blood cells!
HIV waits for a white blood cell to attack it, then
it takes over the white blood cell and makes it
into a virus making factory.
The effect of this is
that other viruses
can now take over
your body and kill
you because your
defenses have been
taken down by the
HIV.
The most effect defenses we have against viral
diseases is vaccination.
Vaccines
Video (3:22)
Viruses cause serious human diseases in addition to AIDS,
such as measles and influenza.
Viral diseases are much more difficult to treat than
bacterial diseases. This is true for a few reasons.
#1 most antibiotics that are used on bacteria disrupt the
bacteria’s cell wall or proteins inside the bacteria.
Since a virus has no cell wall or inner proteins it is immune
to those medicines.
#2 since viruses actually enter healthy cells,
it is hard to find them.
Not only is it difficult to find them but it is hard to kill them
without also killing the cells they are living in.
Herpes
http://www.contemporarypediatrics.com/contpeds/article/articleDetail.jsp?id=108010
Bacteria
Understanding Bacteria VIDEO
(4:00 min)
Although you do not see them, bacteria are
everywhere and affect your life in many
ways.
large intestine: bacteria synthesize
(make) vitamin K, which is essential to
good nutrition
your mouth: may cause
cavities in your teeth
diseases: cholera, typhus,
pneumonia, sexually transmitted
diseases, and tuberculosis
Key
Cocci – round
Bacilli – rod
Spirilli – spiral
Strepto – chains
Staphylo – clusters
Diplo - pairs
prefix
Most species of bacteria are one
of 3 different shapes:
Ex. Bacillus anthracis
Ex. streptococci
Ex. Treponema pallidum = syphilis
Spiral (called spirilli)
Ex. Treponema pallidum = syphilis
Gram Staining
A series of dyes is added to a sample of bacteria
as a microscope slide is being prepared during
the process of gram staining.
Bacteria are either Gram-positive or Gram-negative.
The difference between Gram-negative and Grampositive bacteria is important in diagnosing and treating
diseases caused by bacteria.
Bacteria such as Streptococcus pneumoniae stain
purple during Gram staining and are known as
Gram-positive bacteria.
Bacteria such as
E. coli stain pink
during Gram
staining and are
known as Gramnegative bacteria.
Bacteria do not
undergo mitosis or
meiosis. Instead,
the bacterium first
duplicates its DNA
so that there is
enough DNA for
two cells.
Bacteria Reproduce Rapidly
Then the bacterium splits into two identical cells. Each
cell receives one molecule of DNA and some cytoplasm.
16,777,216 – 33,554,432 – 67,108,864 – 134,217,728
Some bacteria are able to divide as
many as 5 times in one hour.
If you were to place a single bacterium
into a culture dish containing an
abundant (lots) supply of food, you
could find more than 600,000 bacteria in
the dish after only 4 hours.
After 6 hours, the bacterial population
of the dish could reach 476 million!
- 8,388,608 - 4,194,304 - 2,097,152 - 1,048,576 - 524,288 - 262,144 -
4,096 – 8,192 – 16,384 – 32,768 – 65,536 – 131,072
1 -2 – 4 – 8 – 16 – 32 – 64 – 128 – 256 – 512 – 1,024 – 2048 -
Sometimes bacteria do
have a form of sex
called conjugation.
One bacterium reaches
out to another using a
thread-like structure
called a pilus.
The first bacterium transfers part of its DNA to the
other bacterium through the pilus. By this exchange,
bacteria can quickly create or pass along new traits
that help them adapt to different environments.
How Bacteria Obtain Nutrition
A major reason for the success of bacteria is
the wide variety of foods they can use.
Example:
A glass of milk left out of the
refrigerator provides a wealth
of food for bacteria.
Within hours, bacteria
colonize the milk and break
down its supply of sugar,
causing the milk to curdle.
Autotrophs and Heterotrophs
•Some bacteria are
autotrophs.
•Autotrophic organisms
make their own food by
using simple molecules.
•Most bacteria cannot make their own food
and are therefore heterotrophs.
•Many feed on dead animals and animal
wastes; dead plants; and fallen leaves,
Helpful Bacteria
• Fix nitrogen
• Recycle nutrients
• Used to make certain foods and
aid in digestion
– yogurt, olives, sauerkraut, pickles
• Clean up oil and toxic spills - video
• Used to make antibiotics, vitamins, and
drugs
• Used as natural pesticides
(.19)
Bacteria Are Fighting Back
Fight Back video (2.30)
Until the late 1980s, many scientists thought that
we had conquered most infectious bacterial
diseases and that the rest would soon be
controlled.
But, bacteria reproduce
rapidly and mutate.
And, they become
resistant to the drugs
we use against them.