Download 20.1 Viruses

Name
Class
Date
20.1 Viruses
Lesson Objectives
Explain how viruses reproduce.
Explain how viruses cause infection.
BUILD Vocabulary
A. The chart below shows key terms from the lesson with their definitions. Complete the chart by
writing a strategy to help you remember the meaning of each term. One has been done for
you.
Term
Definition
Bacteriophage
Capsid
Infection in which a virus inserts its nucleic acid into the DNA of the host
cell and is duplicated with the cell’s DNA
An infection in which a virus enters a bacterial cell, makes copies of itself,
and causes the cell to burst, or lyse
Prophage
A virus that contains RNA as its genetic material and that copies its
genetic material from RNA to DNA
A nonliving particle made of proteins, nucleic acids, and sometimes lipids,
that can only reproduce by infecting cells
The Discovery of Viruses
Viruses are particles made up of protein, genetic material, and sometimes lipids. The genetic
material in a virus can be RNA or DNA. The protein coat that surrounds the genetic material is
called the capsid.
Follow the directions.
1. Circle the genetic material in each virus.
2. Color the protein parts of each virus red.
T4 Bacteriophage
Head
Tobacco Mosaic Virus
Influenza Virus
Capsid
DNA
Capsid
Answer the questions.
1. Where is the genetic material in a T4 bacteriophage located?
2. In general, is the genetic material in a virus inside or outside the protein parts?
3. Why do you think the word virus, based on the Latin word for poison, was used for these
structures?
BUILD Understanding`
Venn Diagram A Venn diagram is made up of overlapping circles. It is a useful tool for
comparing two or even three topics.
As you read Lesson 1, complete the Venn diagram below with information about viruses and
cells.
Viral Infections
A bacteriophage is a virus that can infect bacteria. A lytic infection is one kind of viral infection.
It results in lysis, or bursting of the host cell.
A lysogenic infection is another kind of viral infection. It occurs when viral DNA inserts itself
into the DNA of the host cell. The viral DNA is replicated along with the host cell DNA.
Eventually, the viral DNA separates from the host DNA. It then directs the construction of new
virus particles.
The diagram below compares lytic and lysogenic infections.
Use the sentences to complete the diagram.
The proteins and nucleic acids assemble into new viruses.
Viral genes are transcribed by the host cell.
The virus injects DNA into a bacterium.
The prophage may replicate with the bacterium for many generations.
Prophage
LYSOGENIC INFECTION
The viral DNA inserts
itself into the bacterial
chromosome, where it
is called a prophage.
LYTIC INFECTION
The prophage can
exit the bacterial
chromosome and
enter a lytic cycle.
Viral enzymes lyse the
bacterium’s cell wall.
The new viruses
escape and infect other
bacterial cells.
The bacterium makes
new viral proteins and
nucleic acids.
Answer the questions.
1. Which type of viral infection includes the formation of a prophage?
2. What happens after viral enzymes lyse the bacterium’s cell wall?
Viral Infections
Lytic Infections In a lytic infection, a virus enters a cell. It then copies itself and causes the
cell to burst. Lysing is another word for this type of cellular destruction.
The flowchart below summarizes what happens in a lytic infection.
Follow the directions.
1. Use the following terms to complete the flowchart.
bacterium
viral proteins
virus
A
enters or injects
its DNA into a
bacterium.
The bacterium
then makes
New viruses are
assembled and
burst out of the
.
and DNA.
Answer the questions.
2. What is one result of a lytic infection? Circle the correct answer.
destruction of the virus
destruction of the host
3. What happens to the viruses after they lyse the cell wall?
BUILD Connections
How a Lytic Virus Is Like an Outlaw An analogy compares two things that are
different and shows how they can be similar.
1. How does the analogy of the lytic virus to an outlaw help you
understand lytic viruses?
20.2 Prokaryotes
Lesson Objectives
Explain how the two groups of prokaryotes differ.
Describe how prokaryotes vary in structure and function.
Explain the role of bacteria in the living world.
BUILD Vocabulary
A. The chart below shows key terms from the lesson with their definitions. Complete the chart by
writing a strategy to help you remember the meaning of each term. One has been done for you.
Term
Definition
Bacillus
A type of asexual reproduction in which a prokaryote replicates its
DNA and divides into two identical halves
Coccus
Conjugation
A thick internal wall that encloses the DNA and part of the
cytoplasm in a prokaryote
A unicellular organism that lacks a nucleus
A spiral- or corkscrew-shaped prokaryote
Classifying Prokaryotes
A prokaryote is a unicellular organism that lacks a nucleus. Prokaryotes are classified into two
groups. Most prokaryotes have a cell wall, a cell membrane, and cytoplasm. The bacterium below
is one example of a prokaryote.
Follow the directions.
1. Color the ribosomes yellow.
2. Color the cell membrane blue.
3. Color the flagellum red.
4. Color the pili orange.
5. Color the DNA green.
Answer the questions.
6. What does the bacterium use to move? Circle the correct answer.
ribosome
flagellum
peptidoglycan
7. Circle the correct answer. Which structure is closest to the environment of the bacterial cell?
outer membrane
cell membrane
cell wall
8. What is the function of the cell wall?
Structure and Function
Size, Shape, and Movement Prokaryotes come in a variety of shapes. Shape is one way to
tell different prokaryotes apart.
The diagram at the right shows several kinds of bacteria.
Follow the directions.
1. Color the bacilli blue.
2. Color the cocci red.
3. Color the spirilla yellow.
Answer the questions.
4. Describe the shape of bacilli.
5. Describe the shape of cocci.
6. Describe the shape of spirilla.
20.3 Diseases Caused by Bacteria and
Viruses
Lesson Objectives
Explain how bacteria cause disease.
Explain how viruses cause disease.
Define emerging disease and explain why emerging diseases are a threat to human health.
Bacterial Diseases
For Questions 1-5, complete each statement by writing the correct word or words.
1. One way bacteria can cause disease is by breaking down and damaging __________________
of the infected organism.
2. Bacteria can also cause disease by releasing ______________ that harm the body.
3. A(n) ______________ is a disease-causing agent.
4. One way to control bacterial growth is by subjecting the bacteria to high temperatures during a
process known as ____________________ .
5. A(n) ________________ is a preparation of weakened or killed pathogens or inactivated toxins
that can prompt the body to produce immunity to a disease.
6. What organs do the bacteria that cause tuberculosis typically damage?
7. What are antibiotics?
8. How are the causes of tuberculosis and diphtheria similar? How are they different?
9. Describe the similarities and differences of antibiotics and disinfectants.
10. Why should meat be cooked until it is well-done?
Match the bacterial control method with an example of the method
Bacterial Control Method
Example
11. physical removal
A. Putting milk in a refrigerator
12. disinfectant
B. Using bleach to clean a countertop
13. safe food storage
C. Using boiling water to clean dishes
14. safe food processing
D. Washing hands
15. sterilization by heat
E. Boiling soup
Viral Diseases
16. What are some human diseases caused by viruses?
17. How do antiviral medications work? Why don’t they also kill host cells?
Write the letter of the correct answer on the line at the left.
_______ 18. A person has a low helper-T cell count. What viral disease does he or she most
likely have?
A. HPV
C. hepatitis B
B. AIDS
D. chicken pox
19. A person has blister-like lesions on the skin. What viral disease does he or she most
likely have?
A. HPV
C. hepatitis B
B. AIDS
D. chicken pox
Emerging Diseases
For Questions 20-24, write True if the statement is true. If the statement is false, change the
underlined word or words to make the statement true.
20. Pathogens are able to evolve over time.
21. A(n) noninfectious disease is an unknown disease that appears in a
population for the first time.
22. The widespread use of vaccines has led to the emergence of resistant
strains of bacteria.
23. Slight genetic changes would be needed for the bird flu virus to become
infectious to humans.
24. Scrapie is most likely caused by pathogens known as viroids.
Apply the Big idea
25. RNA viruses have shown an ability to evade antiviral drugs. How do you suppose this is
possible, when viruses are not alive? How may the reproductive methods of viruses help the
process?
26. Compare the processes of how a bacteria causes a disease verses how a virus causes a
disease.