BIOL 123 · Introductory Biology II
Name: ____________________
Ch. 24 - Part 2 · Viral Diseases and Subviral Agents
LO7. Contrast viral infection of plants and animals, and identify specific diseases caused by
viruses.
1. Describe a difference between the way some viruses enter animal cells compared to
their entry into plant and bacterial cells.
2. SARS-CoV-2 is a single-stranded RNA (ssRNA) enveloped virus. The spike (S) protein that
sticks off of the viral envelope is able to bind to the ACE2 receptor on a host cell. This
binding allows the virus to gain entry into the host cell. Certain lung, intestine, heart,
and kidney cells are the main cell types that express ACE2 in humans and some other
vertebrates.
a. Label the genome, capsid and envelope of SARS-CoV-2 on the image below.
b. Can SARS-CoV-2 infect any cell in the human body? Why or why not?
i.
Similarly, what determines which organisms the virus can infect?
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BIOL 123 · Introductory Biology II
Ch. 24_2 · Viral Diseases and Subviral Agents
3. Use the SARS-CoV-2 viral infection cycle below to answer the following questions.
a. After binding to the host cell, how does the virus gain entry into the cell? In other
words, which process is involved in entry?
b. Does SARS-CoV-2 appear to have a lytic cycle?
c. Identify the following events in the infection cycle of SARS-CoV-2, by placing the
corresponding number in the correct location on the life cycle above.
1. viral RNA released into host cell cytoplasm
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BIOL 123 · Introductory Biology II
2.
3.
4.
5.
6.
7.
Ch. 24_2 · Viral Diseases and Subviral Agents
exocytosis
viral RNA copied
new viral particles assembled
endocytosis
viral RNA translated into viral proteins via host machinery
receptor binding
d. New strains of SARS-CoV-2 have emerged recently. How did these new strains
come about?
4. The first vaccines developed to treat COVID-19 are mRNA vaccines. How do you think
these might work?
a. Which message would the mRNA most likely be carrying (i.e. for which protein)?
b. There have been concerns raised about the safety of mRNA vaccines, as some
people are concerned that the viral mRNA could get into the nucleus of the
human host cell. Is this possible?
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BIOL 123 · Introductory Biology II
Ch. 24_2 · Viral Diseases and Subviral Agents
5. Is SARS-CoV-2 a zoonotic virus? Use the phylogeny above to support your answer.
a. If so, from which animal host did SARS-CoV-2 originate in prior to humans?
LO8. Describe the reproductive cycle of a retrovirus, such as human immunodeficiency virus
(HIV).
6. Below is an image depicting the life cycle of the retrovirus HIV. Steps 3 and 5 are blank in
the image below, as they depict the most important and unique events in the retroviral
life cycle. Next to the 3 and 5 below, write in the events that are depicted.
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BIOL 123 · Introductory Biology II
Ch. 24_2 · Viral Diseases and Subviral Agents
7. What advantage do retroviruses like HIV have over other RNA viruses, such as
SARS-CoV-2?
8. What are two properties of viruses that contribute to their ability to spread and cause
disease so effectively?
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BIOL 123 · Introductory Biology II
Ch. 24_2 · Viral Diseases and Subviral Agents
9. Why are antivirals of limited use in treating viral diseases?
LO9. Describe subviral agents, including prions.
10. Can anything more simple than a virus cause disease? Describe prions, and discuss with
your group why they are interesting from an evolutionary standpoint, and, what might
make them difficult to treat.
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