Download BI101SQ Ch19

General Biology: BI101
Spring, 2007
STUDY QUESTIONS: Ch 19
Bizarre Facts in Biology
Life on the Extreme Edge
by Gail Gasparich
Chapter 19: The Diversity of Viruses, Prokaryotes, and Protists
Imagine life in the most inhospitable of environments, an environment without oxygen or with extremely high salt
concentration, boiling temperatures, or strong acid. How could any organism live there? How could a cell’s plasma
membrane and large molecules remain functional under these conditions? A unique group of microorganisms, the
Archaea, have mastered the art of living on the edge.
Archaeans were first isolated from the hot sulfur springs of Yellowstone National Park. They are classified into
three main groups, depending on their habitat: methanogens
(http://www.space.com/searchforlife/life_methane_020116.html), halophiles, and thermoacidophiles
(http://www.microbe.org/microbes/thermophiles.asp). The methanogens are rod-shaped, live in strictly anaerobic
environments, and produce large quantities of methane (CH4) from carbon dioxide and hydrogen. They live in marshes,
lake bottoms (causing the rotten egg smell that occurs when you poke a stick into the mud at the bottom), and feces
(from the intestines of animals—the cause of intestinal gas). The halophiles require high concentrations of salt, such
as in the Great Salt Lake, Utah. The thermoacidophiles normally grow in hot (100 °C), acidic (pH 1.0) environments.
Researchers are interested in finding out how organisms can live at temperatures that would destroy most biological
molecules, especially enzymes, that are required for all the metabolic processes within a cell. Some of these enzymes
have been exploited for biotechnology. For example, a thermally stable DNA polymerase (used to copy DNA
molecules) was isolated from a thermoacidophile in a hot spring in Yellowstone. This enzyme allowed for the
development of the technique polymerase chain reaction (PCR). The PCR
(http://www.encyclopedia.com/searchpool.asp?target=@DOCTITLE%20polymerase%20chain%20reaction) method
allows scientists to amplify minute amounts of DNA for analysis (for example, from a drop of blood or from a
prehistoric mosquito trapped in amber). This technique has revolutionized the field of forensics and cut the time for
the Human Genome Project from decades to years.
1. If archaeans are the most ancient of organisms on the planet, what do their habitats tell us about the conditions
on Earth 3.5 billion years ago?
2. From what you know about cellular metabolism and about how enzymes function in the cell, how do you think
thermophiles are able to survive at such high temperatures?
Web Investigations:
Agents of Death
Estimated time: 15 minutes
While biological weapons are not new, the bacterial strains, delivery mechanisms, and toxins have become much more
sophisticated. In this exercise we will study biological weapons from a biological, functional, and social perspective.
Have biological weapons been effective in the past? How dangerous are current designs, and what can be done to
defend against them?
1. Take a look at Biological Weapons: A Historical Perspective (http://jama.amaassn.org/cgi/content/short/278/5/412) or the List of Biological Weapons
(http://whyfiles.org/059bio_war/history.html). There are several instances where biological weapons were used in
warfare prior to the 20th century. What organisms were used and how were they dispersed?
2. In recent years, many biological weapons programs have focused on anthrax
(http://www.cdc.gov/ncidod/dbmd/diseaseinfo/anthrax_t.htm), which is caused by Bacillus anthracis. Which people
exposed to anthrax-contaminated mail in 2001 were more likely to die from the resulting infection—people who
touched the mail or people who inhaled the bacterial spores from the mail?
3. Anthrax may be prevented by vaccination (http://www.hopkinsbiodefense.org/pages/agents/agentanthrax2002.html). Why is the use of anthrax as a weapon still of great concern?
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STUDY QUESTIONS: Ch 19
4. The U.S. military has instituted a mandatory Anthrax Vaccine Immunization Program
(http://www.ngwrc.org/news/content/MonNov011000001999.asp). Do you think this is an effective defense
strategy? Can you think of additional or alternative strategies?
Issues in Biology
Why That Prescription for Antibiotics May Be Useless
Bacteria develop resistance to antibiotics when mutations to their DNA occur. If a mutation is favorable and allows
bacteria to survive exposure to antibiotics, then that trait can be selected for by the misuse and abuse of
antibiotics. Conjugation allows bacteria to pass on resistance to antibiotics to bacteria of the same or even different
species: The Battle of the Bugs: Fighting Antibiotic Resistance—How Resistance Occurs
(http://www.fda.gov/fdac/features/2002/402_bugs.html).
There are a number of antibiotics that are no longer as useful as they once were for fighting bacterial infections.
Bacterial diseases that no longer respond as well to antibiotic therapy include tuberculosis, gonorrhea, and staph
infections that often occur following surgery. A more extensive list of microbes now resistant to antibiotics can be
found at Fact Sheet: Antimicrobial Resistance (http://www.niaid.nih.gov/factsheets/antimicro.htm).
What's causing the increasing number of antibiotic-resistant bacteria? There are a number of reasons for the
increases: The Battle of the Bugs: Fighting Antibiotic Resistance—Preserving Antibiotics' Usefulness and From Farm
to Fork (http://www.fda.gov/fdac/features/2002/402_bugs.html). Solving the problem of antibiotic-resistant
bacteria will need to involve doctors, the general public Miracle Drugs vs Superbugs—Too Much of a Good Thing
(http://www.fda.gov/fdac/features/1998/698_bugs.html), and the agricultural industry.
1. What are some of the antibiotics to which bacteria have become resistant?
2. How have physicians contributed to the increase in the number of antibiotic-resistant bacteria?
3. How are antibiotics misused by the agricultural industry?
4. What can the general public (patients) do to prevent further increases in antibiotic-resistant bacteria?
1. What components make up a virus?
a. protein particles only
b. RNA only
c. DNA or RNA and a protein coat
d. DNA and RNA and a protein coat
e. DNA in a nucleus, RNA, ribosomes, plasma membrane, and cell wall
2. By what process, is mRNA made from DNA?
a. replication
b. transcription
c. mitosis
d. evolution
e. translation
3. True or False: Viruses must reproduce in a host cell because they lack organelles needed to duplicate viral
components.
4. Translation of mRNA occurs in the:
a. nucleus.
b. cytoplasm.
c. extracellular fluid.
d. mitochondria.
1. HIV encounters its host cells:
a. via direct contact with another person.
b. via inhalation from the air.
c. by traveling through the blood after entering the body via contact with blood or body fluids.
3. The host cell in which the HIV virus reproduces is a:
a. nerve cell.
b. red blood cell.
4. Reverse transcription is the process by which:
a. DNA is made from RNA.
mRNA is read at the ribosomes.
4. Viruses make new viral copies (reproduce):
a. in water.
b. in the soil.
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c. helper T cell.
d. skin cell.
b. RNA is made from DNA c.. proteins are produced when
c. in a host cell.
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STUDY QUESTIONS: Ch 19
5. After a retrovirus enters its host cell:
a. reverse transcription creates a strand of DNA complementary to the viral RNA.
b. transcription creates mRNA from viral RNA.
c. viral DNA is translated into new viral proteins such as reverse transcriptase.
d. viral DNA and new viral proteins are packaged into pieces of the cell membrane when the new
viruses bud off the cell.
6. After reverse transcription creates viral DNA from the viral RNA, the viral DNA:
a. is translated into new viral proteins.
b. is packaged together with new viral proteins to form new viruses.
c. enters the host cell’s nucleus and is integrated into the host’s chromosome.
d. is used as a template to make new host cell DNA.
e. remains in the cytoplasm where new viruses are assembled.
1. The herpes virus encounters its host cells by:
a. direct contact with another person.
b. traveling through the blood after entering the body via contact with blood or body fluids.
2. The host cell in which the herpes virus reproduces is a:
a. nerve cell.
b. red blood cell.
c. helper T cell.
d. skin cell.
3. After entering a skin cell, _____ in the nucleus of the skin cell.
a. viral RNA is copied into DNA b. mRNA is translated into viral proteins c. viral DNA is copied
d. RNA, viral proteins, and envelope proteins are assembled into new herpes viruses
4. After viral DNA and viral and envelope proteins are assembled into new viruses, they exit the host cell via:
a. transcription.
b. exocytosis.
c. mitosis.
d. endocytosis. e. translation.
1. The genetic material is chemically known as:
a. DNA.
b. RNA.
c. protein.
2. (True or False) A segment of DNA that codes for a complete protein is a gene.
3. The DNA of an organism is usually arranged into discrete, contiguous lengths known as:
a. genes.
b. chromosomes.
c. plasmids.
5. Prokaryotes have:
a. no true nucleus.
b. no membranous organelles.
c. a large, circular chromosome.
d. both a. and b. are true
e. a, b and c are all true
1. During bacterial conjugation, the transferred item is a:
a. gene.
b. chromosome.
c. plasmid.
d. lipid.
e. protein.
2. At the end of conjugation:
a. one cell has lost a plasmid, while the other has gained one.
b. one cell has lost a chromosome, while the other has gained one.
c. the two cells have had an equal exchange of plasmids.
7. At the end of conjugation the recipient bacterium ends up with some new genes, which may endow it with new
capabilities, such as:
a. the ability to resist antibiotics.
b. the ability to undergo mitosis.
c. the ability to undergo meiosis.
d. flagellar motility.
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8. Sexual reproduction performed by eukaryotes is similar to bacterial conjugation because:
a. two haploid cells fuse.
b. genetic variability increases.
c. crossing over occurs
d. genetically different diploid offspring form.
Thinking Through the Concepts
1. Describe the structure of a typical virus. How do viruses replicate?
2. List the major differences between prokaryotes and protists.
3. Describe some of the ways in which bacteria obtain energy and nutrients.
4. What are nitrogen-fixing bacteria, and what role do they play in ecosystems?
5. What is an endospore? What is its function?
6. Describe some examples of bacterial symbiosis.
7. What is the importance of dinoflagellates in marine ecosystems? What happens when they reproduce rapidly?
8. What is the major ecological role played by single-celled algae?
9. What protist group consists entirely of parasitic forms?
Essay Challenge
1. Contrast the three noncellular infectious agents.
2. How are viruses able to reproduce when they lack the organelles needed to create new genetic material and
protein coats?
4. Of what importance to a food chain are the algae?
5. A. How does the ability of bacteria to perform conjugation benefit bacteria?
B. Of what concern to humans is the ability of bacteria to perform conjugation?
6. You've been given a beaker of water containing unidentified microbes and are charged with determining what kind
of microbes are present in the water.
You perform the following tests:
Add solution A which glows when it binds to a nuclear membrane.
Add solution B which fizzes in the presence of DNA.
Add solution C which turns blue in the presence of chloroplasts.
Add solution D which creates a bad odor when peptidoglycan is present.
Your results are: no glow, fizzing, no color change, and a bad odor.
A. What kind of microbes are present in the water? Explain your answer.
B. Of what importance are these microbes to other organisms?
7. How are cyanobacteria and algae similar to and different from each other?
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Figure Caption Questions and Answers
Figure 19-2 Viral structure and replication
Question: Why are viruses unable to replicate outside of a host cell?
Figure 19-4 Some viruses infect bacteria
Question: In biotechnology, viruses are often used to transfer genes from the cells of one species to the
cells of another. Which properties of viruses make them useful for this purpose?
Figure 19-9 Spores protect some bacteria
Question: What might explain the observation that most endospore-forming bacteria are species that live in
soil?
Figure 19-10 Reproduction in prokaryotes
Question: What is the main advantage of binary fission, compared to sexual reproduction?
Figure 19-12 Some prokaryotes thrive in extreme conditions
Question: Some of the enzymes that have important uses in molecular biology procedures are extracted
from prokaryotes that live in hot springs. Can you guess why?
Figure 19-14 Nitrogen-fixing bacteria in root nodules
Question: If all of Earth’s nitrogen-fixing prokaryotes were to die suddenly, what would happen to the
concentration of nitrogen gas in the atmosphere?
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