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Viruses and Bacteria
Table of Contents
Viruses
Bacteria
Viruses, Bacteria, and Your Health
Viruses and Bacteria - Viruses
What Is a Virus?
A virus is a tiny nonliving particle
that enters and then reproduces
inside a living cell.
Virus particles are tiny compared
to bacteria.
Like organisms- can multiply
Host- provide food and energy
Parasite- live on the host and
cause them harm
Viruses and Bacteria - Viruses
The Structure of Viruses
All viruses have two basic parts: a protein coat that protects
the virus and an inner core made of genetic material. Some
viruses are surrounded by an outer membrane envelope.
Viruses and Bacteria - Viruses
How Viruses Multiply
Active viruses enter cells and immediately begin to multiply,
leading to the quick death of the invaded cells.
Viruses and Bacteria - Viruses
Diameter
The diameter of a circle is a line that passes through the
center of the circle and has both of its endpoints on the
circle. To find the diameter, draw a line like the one shown
below. Then use a metric ruler to measure the length of the
line. For example, the diameter of a penny is about 1.9 mm.
Viruses and Bacteria - Viruses
Diameter
Practice Problem
Measure the diameter
of a quarter.
2.4 cm
Viruses and Bacteria - Viruses
Diameter
Practice Problem
Measure the diameter
of a CD.
12 cm
Viruses and Bacteria - Viruses
How Viruses Multiply
Hidden viruses “hide” for a while inside host cells before
becoming active.
Viruses and Bacteria - Viruses
Active and Hidden Viruses Activity
Click the Active Art button to open a browser window and
access Active Art about active and hidden viruses.
Viruses and Bacteria - Viruses
Sequencing
As you read, make two flowcharts that show how active and
hidden viruses multiply. Put the steps in the process in
separate boxes in the flowchart, in the order in which they
occur.
How Active Viruses Multiply
Virus attaches to the surface of a living cell.
Virus injects genetic material into cell.
Cell produces viral proteins and genetic material.
Viruses assemble.
Cell bursts, releasing viruses.
Viruses and Bacteria - Viruses
Sequencing
As you read, make two flowcharts that show how active and
hidden viruses multiply. Put the steps in the process in
separate boxes in the flowchart, in the order in which they
occur.
How Hidden Viruses Multiply
Virus attaches to cell.
Virus injects its genetic material.
Virus’s genetic material becomes part of cell’s genetic material.
Cell produces viral proteins and genetic material.
Viruses are assembled.
Cell bursts, releasing viruses.
Viruses and Bacteria - Viruses
Deadly Virus
Click the Video button to watch a movie
about deadly viruses.
Viruses and Bacteria
End of Section:
Viruses
Viruses and Bacteria - Bacteria
The Bacterial Cell
Bacteria are
prokaryotes. The
genetic material in the
cells is not contained
in a nucleus.
Single cell organisms
Small (µm/mm)
Shape: spherical,
rodlike, spiral)
Viruses and Bacteria
Bacteria
Food and energy
• Some are autotrophs-make their own food: use sun’s
energy or energy from chemical elements
• Some are heterotrophs: can’t make their own food( ex:
milk, meat, leaves)
• Respiration: make energy by breaking down the food
Reproduction
Asexual- cell divides into identical cells; one parent cell
Sexual – two parent cells- conjugation ( transfer of genetic
material)- cells with new genetic material
Endospore formation
Unfavorable conditions- endospore ( genetic
material+cytoplasm)
Viruses and Bacteria
Role of Bacteria
•
•
•
•
•
Oxygen production
Food production
Environment recycling
Environmental clean up
Health and medicine
Viruses and Bacteria - Bacteria
Population Explosion
Suppose a bacterium
reproduces by binary fission
every 20 minutes. The new cells
survive and reproduce at the
same rate. This graph shows
how the bacterial population
would grow from a single
bacterium.
Viruses and Bacteria - Bacteria
Population Explosion
Reading Graphs:
What variable is being
plotted on the horizontal
axis? What is being
plotted on the vertical
axis?
Horizontal axis–time
(minutes); vertical axis–
number of bacterial cells.
Viruses and Bacteria - Bacteria
Population Explosion
Interpreting Data:
According to the graph,
how many cells are there
after 20 minutes? One
hour? Two hours?
2 cells after 20 minutes;
8 cells after one hour;
64 cells after two hours.
Viruses and Bacteria - Bacteria
Population Explosion
Drawing Conclusions:
Describe the pattern you
see in the way the
bacterial population
increases over two hours.
The number of cells doubles
with each division.
Viruses and Bacteria - Bacteria
Population Explosion
Predicting:
Do you think the bacterial
population will continue to
grow at the same rate?
Why or why not?
Not likely. The bacteria will
continue to reproduce at this
rate only as long as the
conditions are favorable.
Viruses and Bacteria - Bacteria
Building Vocabulary
After you read the section, reread the paragraphs that
contain definitions of Key Terms. Use all the information you
have learned to write a definition of each Key Term in your
own words.
Key Terms:
bacteria reproduction
flagellum
asexual
endospore
pasteurization
respiration
sexual
reproduction
cytoplasm
binary fission
decomposer
ribosome
conjugation
Examples:
AnLeeuwenhoek
If
A
Asexual
bacterial
endospore
reproduction
cell may
ishad
a small,
also
owned
ishave
a
rounded,
reproductive
one
a flagellum,
of the
thick-walled,
high-powered
process
a long,that
microscopes
whiplike
involves
resting
cell
structure
only
that
in
one
use
forms
parent
that
today,
inside
helps
and
heaproduces
would
cell
bacterial
tohave
move.
offspring
cell.
seen the
that
single-celled
are
to
organisms
the
parent.
known
as bacteria
Theidentical
During
process
pasteurization,
of
breaking
food
down
is food
heated
to release
to a in detail.
its
Sexual
reproduction
involves
two
parents
who
The region
inside
cellenough
membrane,
the
energy
temperature
is called
thatrespiration.
isthe
high
to killcalled
most harmful
combine
their
genetic
material
to
produce
a
new
cytoplasm,
contains
material.
bacteria
changing
the taste
of the
food.
Bacteria without
reproduce
byaagel-like
process
called
binary
organism, which differs from both parents.
fission,
in
one cell
divides
to
form
identical
These
bacteria,
which
liveare
in the
are twocalled
Located
in which
the cytoplasm
tinysoil,
structures
During
a
process
called
conjugation,
one
bacterium
cells.
decomposers—organisms
thatwhere
break proteins
down large
ribosomes, chemical factories
are
transfers some of its genetic material to another
chemicals
produced. in dead organisms into small chemicals.
bacterium through a thin, threadlike bridge that joins
the two cells.
Viruses and Bacteria - Bacteria
More on Bacteria
Click the PHSchool.com button
for an activity about bacteria.
Viruses and Bacteria
End of Section:
Bacteria
Viruses and Bacteria - Viruses, Bacteria, and Your Health
Common Bacterial Diseases
Many bacterial diseases can be cured with antibiotics.
Viruses and Bacteria - Viruses, Bacteria, and Your Health
Common Viral Diseases
Unlike with bacterial diseases, there are currently no
medications that can cure viral infections.
Viruses and Bacteria - Viruses, Bacteria, and Your Health
Using Prior Knowledge
Look at the section headings and visuals to see what this
section is about. Then write what you already know about
diseases caused by viruses and bacteria in a graphic
organizer like the one below. As you read, write what you
learn.
What You Know
1.
2.
You can catch a cold from somebody who has one.
Some diseases can be treated with medicines.
What You Learned
1.
2.
You can catch diseases through contact with an infected person, a
contaminated object, an infected animal, or an environmental source.
Antibiotic resistance results when some bacteria are able to survive in
the presence of an antibiotic.
Viruses and Bacteria - Viruses, Bacteria, and Your Health
Antibiotic Resistance
Click the Video button to watch a movie
about antibiotic resistance.
Viruses and Bacteria - Viruses, Bacteria, and Your Health
Links on Infectious Diseases
Click the SciLinks button for links on infectious diseases.
Viruses and Bacteria
End of Section:
Viruses, Bacteria,
and Your Health
Viruses and Bacteria
Graphic Organizer
Nonliving
Can be
useful
Treated with
antibiotics
Viruses and Bacteria
End of Section:
Graphic Organizer