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Microbiology Unit Outline Name _______________________
Chapter 10: The Genetics of Viruses and Bacteria
10.17 Viral DNA may become part of the host chromosome
1. A virus is essentially “genes in a box,” an infectious particle consisting of a bit of nucleic acid,
wrapped in a protein coat called a capsid, and in some cases, a membrane envelope.
2. Viruses have two types of reproductive cycles.
a. In the lytic cycle viral particles are produced using host cell components, the host cell lyses, and
viruses are released.
b. Lysogenic cycle
i. Viral DNA is inserted into the host chromosome by recombination.
ii. Viral DNA is duplicated along with the host chromosome during each cell division.
iii. The inserted phage DNA is called a prophage. Most prophage genes are inactive.
iv. Environmental signals can cause a switch to the lytic cycle, causing the viral
DNA to be excised from the bacterial chromosome and leading to the death of the host cell.
10.18 Many viruses cause disease in animals and plants
1. Viruses can cause disease in animals and plants.
2. DNA viruses and RNA viruses cause disease in animals.
3. A typical animal virus has a membranous outer envelope and projecting spikes of glycoprotein.
4. The envelope helps the virus enter and leave the host cell.
5. Many animal viruses have RNA rather than DNA as their genetic material. These include viruses that
cause the common cold, measles, mumps, polio, and AIDS.
6. The reproductive cycle of the mumps virus, a typical enveloped RNA virus, has seven major steps:
a. entry of the protein-coated RNA into the cell
b. uncoating—the removal of the protein coat
c. RNA synthesis—mRNA synthesis using a viral enzyme
d. protein synthesis—mRNA is used to make viral proteins
e. new viral genome production—mRNA is used as a template to synthesize new
viral genomes
f. assembly—the new coat proteins assemble around the new viral RNA
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g. exit—the viruses leave the cell by cloaking themselves in the host cell’s plasma
membrane.
7. Some animal viruses, such as herpes viruses, reproduce in the cell nucleus.
8. Most plant viruses are RNA viruses.
a. To infect a plant, they must get past the outer protective layer of the plant.
b. Viruses spread from cell to cell through plasmodesmata.
c. Infection can spread to other plants by insects, herbivores, humans, or farming tools.
9. There are no cures for most viral diseases of plants or animals.
10.19 Emerging viruses threaten human health
1. Viruses that appear suddenly or are new to medical scientists are called emerging viruses. These
include the AIDS virus, Ebola virus, West Nile virus, and SARS virus.
2. Three processes contribute to the emergence of viral diseases:
a. mutation—RNA viruses mutate rapidly.
b. contact between species—viruses from other animals spread to humans.
c. spread from isolated human populations to larger human populations, often over great distances.
10.20 The AIDS virus makes DNA on an RNA template
1. AIDS (acquired immunodeficiency syndrome) is caused by HIV (human immunodeficiency virus).
2. HIV
a. is an RNA virus, has two copies of its RNA genome,
b. carries molecules of reverse transcriptase, which causes reverse transcription, producing DNA
from an RNA template.
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3. After HIV RNA is uncoated in the cytoplasm of the host cell,
a. reverse transcriptase makes one DNA strand from RNA, reverse transcriptase adds a
complementary DNA strand
b. double-stranded viral DNA enters the nucleus and integrates into the chromosome, becoming a
provirus, the provirus DNA is used to produce more mRNA copies
c. the viral mRNA is translated to produce viral proteins, and new viral particles are assembled, leave
the host cell, and can then infect other cells.
10.21 Viroids and prions are formidable pathogens in plants and animals
1. Some infectious agents are made only of RNA or protein.
a. Viroids are small, circular RNA molecules that infect plants. Viroids replicate within host cells
without producing proteins and interfere with plant growth.
b. Prions are infectious proteins that cause degenerative brain diseases in animals.
Prions- appear to be misfolded forms of normal brain proteins & which convert normal protein to
misfolded form.
Viruses Prions
Infectious agents that is made up of a nucleic
acid in a protein coat.
Infectious protein particle.
Simple particle that is able to multiply only
within the living cells of a host
Less complex than a virus. Body cell proteins
misfold when prion is present.
Can cause a wide variety of infections Mainly causes neuro-degenerative diseases
10.22 Bacteria can transfer DNA in three ways
1. Viral reproduction allows researchers to learn more about the mechanisms that regulate DNA
replication and gene expression in living cells.
2. Bacteria are also valuable but for different reasons.
a. Bacterial DNA is found in a single, closed loop chromosome.
b. Bacterial cells divide by replication of the bacterial chromosome and then by binary fission.
c. Because binary fission is an asexual process, bacteria in a colony are genetically identical to the
parent cell.
3. Bacteria use three mechanisms to move genes from cell to cell.
4. Once new DNA gets into a bacterial cell, part of it may then integrate into the recipient’s
chromosome.
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a. Transformation is the
uptake of DNA from the
surrounding environment.
b. Transduction is gene transfer
by phages.
c. Conjugation is the transfer of
DNA from a donor to a recipient
bacterial cell through a cytoplasmic
(mating) bridge.
10.23 Bacterial plasmids can serve as carriers for gene transfer
1. The ability of a donor E. coli cell to carry out conjugation is usually due to a specific piece of DNA
called the F factor.
2. During conjugation, the F factor is integrated into the bacterium’s chromosome.
3. The donor chromosome starts replicating at the F factor’s origin of replication.
4. The growing copy of the DNA peels off and heads into the recipient cell.
5. The F factor serves as the leading end of the transferred DNA.
6. An F factor can also exist as a plasmid, a small circular DNA molecule separate from the bacterial
chromosome.
a. Some plasmids, including the F factor, can bring about conjugation and move to
another cell in linear form.
b. The transferred plasmid re-forms a circle in the recipient cell.
Chapter 16: Prokaryotes
Introduction
A. The abundant life of a coral reef depends upon microbes.
1. Photosynthesis by protists and prokaryotes feed all of the animals.
2. Prokaryotes convert dead organic material into fertilizer.
3. Protists that reside in the cells of corals use photosynthesis to produce sugars that nourish their hosts.
B. Prokaryotes and protists are essential to the health of every ecosystem, including the human body.
Prokaryotes
16.1 Prokaryotes are diverse and widespread
1. Prokaryotic cells are smaller than eukaryotic cells.
a. Prokaryotes range from 1–5 µm in diameter.
b. Eukaryotes range from 10–100 µm in diameter.
2. The collective biomass of prokaryotes is at least 10 times that of all eukaryotes.
3. Prokaryotes live in habitats too cold, too hot, too salty, too acidic, and too alkaline for eukaryotes to
survive.
4. Some bacteria are pathogens, causing disease. But most bacteria on our bodies are benign or
beneficial.
5. Several hundred species of bacteria live in and on our bodies
a. decomposing dead skin cells
b. supplying essential vitamins
c. guarding against pathogenic organisms
6. Prokaryotes in soil decompose dead organisms, sustaining chemical cycles.
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16.2 External features contribute to the success of prokaryotes
1. Prokaryotic cells have three common cell shapes.
a. Cocci are spherical prokaryotic cells. They sometimes occur in chains that are called streptococci.
b. Bacilli are rod-shaped prokaryotes. Bacilli may also be threadlike, or filamentous.
c. Spiral prokaryotes are like a corkscrew.
i. Short and rigid prokaryotes are called spirilla.
ii. Longer, more flexible cells are called spirochetes.
2. Nearly all prokaryotes have a cell wall. Cell walls provide physical protection and prevent the cell
from bursting in a hypotonic environment.
3. When stained with Gram stain, cell walls of bacteria are either
a. Gram-positive, with simpler cell walls containing peptidoglycan
b. Gram-negative, with less peptidoglycan and are more complex and more likely to cause disease.
4. The cell wall of many prokaryotes is covered by a capsule, a sticky layer of polysaccharides or
protein.
5. The capsule
a. enables prokaryotes to adhere to their substrate or to other individuals in a colony
b. shields pathogenic prokaryotes from attacks by a host’s immune system.
6. Some prokaryotes have external structures that extend beyond the cell wall.
a. Flagella help prokaryotes move in their environment.
b. Hairlike projections called fimbriae enable prokaryotes to stick to their substrate or each other.
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16.3 Populations of prokaryotes can adapt rapidly to changes in the environment
1. Prokaryote population growth
a. occurs by binary fission & can rapidly produce a new generation within hours
b. can generate a great deal of genetic variation by spontaneous mutations increasing the likelihood
that some members of the population will survive changes in the environment.
2. The genome of a prokaryote typically
a. has about one-thousandth as much DNA as a eukaryotic genome
b. is one long, circular chromosome packed into a distinct region of the cell.
3. Many prokaryotes also have additional small, circular DNA molecules called plasmids, which
replicate independently of the chromosome.
4. Some prokaryotes form specialized cells called endospores that remain dormant through harsh
conditions.
5. Endospores can survive extreme heat or cold.
16.4 Prokaryotes have unparalleled nutritional diversity
1. Prokaryotes exhibit much more nutritional diversity than eukaryotes.
2. Two sources of energy are used.
a. Phototrophs capture energy from sunlight.
b. Chemotrophs harness the energy stored in chemicals.
3. Two sources of carbon are used by prokaryotes.
a. Autotrophs obtain carbon atoms from carbon dioxide.
b. Heterotrophs obtain their carbon atoms from the organic compounds present in other organisms.
4. The terms that describe how prokaryotes obtain energy and carbon are combined to describe their
modes of nutrition.
a. Photoautotrophs obtain energy from sunlight and use carbon dioxide for carbon.
b. Photoheterotrophs obtain energy from sunlight but get their carbon atoms from organic
molecules.
c. Chemoautotrophs harvest energy from inorganic chemicals and use carbon dioxide for carbon.
d. Chemoheterotrophs acquire energy and carbon from organic molecules.
16.10 Some bacteria cause disease
1. All organisms are almost constantly exposed to pathogenic bacteria.
2. Most bacteria that cause illness do so by producing a poison.
a. Exotoxins are proteins that bacterial cells secrete into their environment.
b. Endotoxins are components of the outer membrane of gram-negative bacteria.
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Chapter 24 The Immune System
Adaptive Immunity
24.4 The adaptive immune response counters specific invaders
1. Our immune system responds to foreign molecules called antigens, which elicit the adaptive immune
response.
2. The adaptive immune system is found only in the vertebrates, reacts to specific pathogens, and
“remembers” an invader.
3. Infection or vaccination triggers active immunity.
4. Vaccination, or immunization, exposes the immune system to a vaccine, a harmless variant or part
of a disease-causing microbe.
5. Antibodies are proteins produced in response to and counteracting a specific antigen. Antibodies
combine chemically with substances which the body recognizes as foreign to inactivate and mark for
destruction.
Immune Response to Antigens
24.13 HIV destroys helper T cells, compromising the body’s defenses
1. AIDS (acquired immunodeficiency syndrome), results from infection by HIV, the human
immunodeficiency virus.
a. Since 1981, AIDS has killed more than 27 million people and more than 33 million people live
today with HIV.
b. Most AIDS infections and deaths occur in non-industrialized nations of southern Asia and sub-
Saharan Africa.
2. The AIDS virus attacks helper T cells responsible for identifying foreign invaders. This opens
the way for other infections.
3. AIDS patients typically die from other infections and cancers that would normally be resisted by a
person with a healthy immune system.
4. Current medications, antivirals, help to control the amount of viruses produced, but do not cure HIV.
24.14 The rapid evolution of HIV complicates AIDS treatment
1. HIV mutates very quickly.
2. New strains are resistant to AIDS drugs.
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Vocabulary for Microbiology Unit
1. virus- A microscopic particle capable of infecting cells of living organisms and inserting its genetic material.
Viruses are generally not considered to be alive because they do not display all of the characteristics associated with life.
2. capsid- The protein shell that encloses a viral genome. It may be rod-shaped, polyhedral, or more complex in shape.
3. lytic cycle- A type of viral replication cycle resulting in the release of new viruses by lysis (breaking open) of
the host cell.
4. lysogenic cycle- A type of bacteriophage replication cycle in which the viral genome is incorporated into the
bacterial host chromosome as a prophage. New phages are not produced, and the host cell is not killed or lysed unless the viral genome leaves the host chromosome.
5. prophage- Phage DNA that has inserted by genetic recombination into the DNA of a prokaryotic
chromosome.
6. AIDS (acquired immunodeficiency syndrome)- Acquired immunodeficiency syndrome; the late stages of
HIV infection, characterized by a reduced number of T cells and the appearance of characteristic opportunistic infections.
7. HIV (human immunodeficiency virus)- Human immunodeficiency virus, the retrovirus that attacks the human immune system and causes AIDS.
8. reverse transcriptase- An enzyme used by retroviruses that catalyzes the synthesis of DNA on an RNA
template.
9. retrovirus- An RNA virus that reproduces by means of a DNA molecule. It reverse-transcribes its
RNA into DNA, inserts the DNA into a cellular chromosome, and then transcribes more copies of the RNA from the viral DNA. HIV and a number of cancer-causing viruses are retroviruses.
10. viroid- A plant pathogen composed of molecules of naked, circular RNA several hundred nucleotides long.
11. prion- An infectious form of protein that may multiply by converting related proteins into more
prions. Prions cause several related diseases in different animals, including scrapie in sheep and mad
cow disease.
12. transformation- The incorporation of new genes into a cell from DNA that the cell takes up from
the surrounding environment.
13. transduction- The transfer of bacterial genes from one bacterial cell to another by a phage.
14. conjugation- The union (mating) of two bacterial cells or protist cells and the transfer of DNA between the two cells.
15. F factor- A piece of DNA that can exist as a bacterial plasmid. The F factor carries genes for making sex pili and other structures needed for conjugation, as well as a site where DNA replication
can start. F stands for fertility.
16. plasmid- A small ring of independently replicating DNA separate from the main chromosome(s).
Plasmids are found in prokaryotes and yeast.
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17. archaea- one of two prokaryotic domains of life
18. autotroph- an organism that makes its own food (often by photosynthesis), thereby sustaining itself without
eating other organisms or their molecules. Plants, algae, and numerous bacteria are autotrophs
19. bacillus (plural, bacilli)- A rod-shaped prokaryotic cell
20. bacteria- One of two prokaryotic domains of life
21. biofilm- a surface-coating colony of prokaryotes that engage in metabolic cooperation.
22. bioremediation- The use of living organisms to detoxify and restore polluted and degraded ecosystems.
23. chemoautotroph- An organism that obtains both energy and carbon from inorganic chemicals. A
chemoautotroph makes its own organic compounds from CO2 without using light energy
24. chemoheterotroph- An organism that obtains both energy and carbon from organic compounds.
25. coccus (plural, cocci)- A spherical prokaryotic cell
26. cyanobacteria- Photoautotrophic prokaryotes with plantlike, oxygen-generating photosynthesis.
27. endospore- A thick-coated, protective cell produced within a bacterial cell. The endospore becomes
dormant and is able to survive harsh environmental conditions.
28. endotoxin- A poisonous component of the outer membrane of gram-negative bacteria that is released
only when the bacteria die.
29. exotoxin- A poisonous protein secreted by certain bacteria.
30. fimbriae- One of the short, hairlike projections on some prokaryotic cells that help attach the cells to their substrate or to other cells.
31. gram stain- Microbiological technique to identify the cell wall composition of bacteria. Results categorize bacteria as gram-positive or gram-negative.
32. gram-positive bacteria- Diverse group of bacteria with a cell wall that is structurally less complex and contains more peptidoglycan than that of gram-negative bacteria. Gram-positive bacteria are usually less toxic
than gram-negative bacteria.
33. heterotroph- An organism that obtains organic food molecules by eating other organisms or substances derived from them; a consumer or a decomposer in a food chain
34. parasite- Organism that derives its nutrition from a living host, which is harmed by the interaction.
35. pathogen- An agent, such as a virus, bacteria, or fungus, that causes diseases.
36. peptidoglycan- A polymer of complex sugars cross-linked by short polypeptides; a material unique to bacterial cell walls.
37. photoautotroph- An organism that obtains energy from sunlight and carbon from CO2 using the process of photosynthesis.
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38. photoheterotroph- An organism that obtains energy from sunlight and carbon from organic sources.
39. spirochetes- A member of a group of helical bacteria that spiral through the environment by means
of rotating, internal filaments.
40. antigens- A foreign (nonself) molecule that elicits an adaptive immune response
41. active immunity- Immunity conferred by recovering from an infectious disease or by receiving a vaccine
42. vaccination- A procedure that presents the immune system with a harmless variant or derivative of a
pathogen, thereby stimulating the adaptive immune system to mount a long term defense against the pathogen.
43. antibodies- A protein dissolved in blood plasma that attaches to a specific kind of antigen and helps counter
its effects; secreted by plasma cells
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EXTRA
16.9 Bacteria include a diverse assemblage of prokaryotes.
1. The domain Bacteria is currently divided into five groups, based on comparisons of
genetic sequences.
a. Proteobacteria
i. are all gram negative,
ii. share a particular rRNA sequence, and
iii. represent all four modes of nutrition.
iv. Thiomargarita namibiensis is a type of proteobacteria that
(I) is a giant among prokaryotes, typically ranging up to 100–300 microns in
diameter,
(II) uses H2S to generate organic molecules from CO2, and
(III) produces sulfur wastes.
v. Proteobacteria also include Rhizobium species that
(I) live symbiotically in root nodules of legumes and
(II) convert atmospheric nitrogen gas into a form usable by their legume host.
(III) Symbiosis is a close association between organisms of two or more
species.
(IV) Rhizobium is an endosymbiont, living within another species.
b. Gram-positive bacteria
i. rival proteobacteria in diversity and
ii. include the actinomycetes common in soil.
iii. Streptomyces is often cultured by pharmaceutical companies as a source of many antibiotics.
c. Cyanobacteria
i. Cyanobacteria are the only group of prokaryotes with plantlike, oxygen-generating
photosynthesis.
ii. Some species, such as Anabaena, have specialized cells that fix nitrogen.
d. Chlamydias
i. Chlamydias live inside eukaryotic host cells.
ii. Chlamydia trachomatis
(I) is a common cause of blindness in developing countries and
(II) is the most common sexually transmitted disease in the United States.
e. Spirochetes are
i. helical bacteria and
ii. notorious pathogens, causing
(I) syphilis and
(II) Lyme disease.
16.10 CONNECTION: Some bacteria cause disease
1. All organisms are almost constantly exposed to pathogenic bacteria.
2. Most bacteria that cause illness do so by producing a poison.
a. Exotoxins are proteins that bacterial cells secrete into their environment.
b. Endotoxins are components of the outer membrane of gram-negative bacteria.
16.11 SCIENTIFIC DISCOVERY: Koch’s postulates are used to prove that a bacterium causes a disease
1. Koch’s postulates are four essential conditions used to establish that a certain bacterium is the cause
of a disease. They are
a. find the bacterium in every case of the disease,
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b. isolate bacteria from a person who has the disease and grow it in pure culture,
c. show that the cultured bacteria cause the disease when transferred to a healthy subject, and
d. isolate the bacteria from the experimentally infected subject.
2. Koch’s postulates were used to demonstrate that the bacterium Helicobacter pylori is the cause of
most peptic ulcers.
3. The 2005 Nobel Prize in Medicine was awarded to Barry Marshall and Robin Warren for this
discovery.
16.12 CONNECTION: Bacteria can be used as biological weapons
1. Bacteria that cause anthrax and the plague can be used as biological weapons.
a. Bacillus anthracis killed five people in the United States in 2001.
b. Yersinia pestis bacteria
i. are typically carried by rodents and transmitted by fleas, causing the plague and
ii. can cause a pneumonic form of plague if inhaled.
2. Clostridium botulinum produces the exotoxin botulinum, the deadliest poison on earth.
3. Botulinum blocks transmission of nerve signals and prevents muscle contraction.
Ch. 24 The Immune System
Introduction
A. Neutrophils are
1. a kind of white blood cell,
2. capable of recognizing and destroying foreign invaders, and
3. part of the body’s immune system.
B. The human body’s immune system
1. recognizes agents that cause disease and
2. attacks them.
Innate Immunity
24.1 All animals have innate immunity
1. Nearly everything in the environment teems with pathogens, agents that cause
disease.
2. The immune system is the body’s system of defenses against agents that cause disease.
3. Innate immunity is a series of defenses that
a. act immediately upon infection and
b. are the same whether or not the pathogen has been encountered before.
4. Invertebrates rely solely on innate immunity, which may consist of
a. an exoskeleton,
b. low pH,
c. the enzyme lysozyme, and
d. immune cells capable of phagocytosis, cellular ingestion and digestion of foreign
substances.
5. Vertebrates have innate and adaptive immunity.
6. Vertebrate innate immunity includes
a. barriers such as skin and mucous membranes,
b. interferons, proteins produced by virus-infected cells, that help to limit the cell-to-cell spread of
viruses,
c. neutrophils (phagocytic cells),
d. macrophages, large phagocytic cells that wander through the interstitial fluid,
e. natural killer cells that attack cancer cells and virus-infected cells, and
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f. a complement system, a group of about 30 kinds of proteins that can act with other defense
mechanisms.
24.2 Inflammation mobilizes the innate immune response
1. Tissue damage triggers the inflammatory response, a major component of our innate immunity,
which can
a. disinfect and clean infected tissues and
b. limit the spread of infection to surrounding tissues.
2. Bacterial infections can bring about an overwhelming systemic inflammatory response leading to
septic shock, characterized by
a. very high fever and
b. low blood pressure.
24.3 The lymphatic system becomes a crucial battleground during infection
1. The lymphatic system is
a. involved in innate and adaptive immunity and
b. consists of a network of
i. lymphatic vessels,
ii. lymph nodes, and
iii. lymph.
2. Lymphatic vessels
a. collect fluid from body tissues and
b. return it as lymph to the blood.
3. Lymph organs
a. include the spleen and lymph nodes and
b. are packed with white blood cells that fight infections.
4. As lymph circulates through lymphatic organs it
a. collects
i. microbes,
ii. parts of microbes, and
iii. microbial toxins, and
b. transports them to lymphatic organs where
i. macrophages in lymphatic organs engulf the invaders and
ii. lymphocytes may mount an adaptive immune response.
Adaptive Immunity
24.4 The adaptive immune response counters specific invaders
1. Our immune system responds to foreign molecules called antigens, which elicit the adaptive immune
response.
2. The adaptive immune system
a. is found only in the vertebrates,
b. reacts to specific pathogens, and
c. “remembers” an invader.
3. Infection or vaccination triggers active immunity.
4. Vaccination, or immunization, exposes the immune system to a vaccine,
a. a harmless variant or
b. part of a disease-causing microbe.
5. We can temporarily acquire passive immunity by receiving premade antibodies.
24.5 Lymphocytes mount a dual defense
1. Lymphocytes
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a. are white blood cells that spend most of their time in the tissues and organs of the lymphatic
system,
b. are responsible for adaptive immunity, and
c. originate from stem cells in the bone marrow.
i. B lymphocytes or B cells continue developing in bone marrow.
ii. T lymphocytes or T cells develop further in the thymus.
2. B cells
a. participate in the humoral immune response and
b. secrete antibodies into the blood and lymph.
3. T cells
a. participate in the cell-mediated immune response,
b. attack cells infected with bacteria or viruses, and
c. promote phagocytosis by other white blood cells and by stimulating B cells to
produce antibodies.
4. Millions of kinds of B cells and T cells
a. each with different antigen receptors, capable of binding one specific type of
antigen,
b. wait in the lymphatic system,
c. where they may respond to invaders.
4.13 CONNECTION: HIV destroys helper T cells, compromising the body’s defenses
1. AIDS (acquired immunodeficiency syndrome), results from infection by HIV, the human
immunodeficiency virus.
a. Since 1981, AIDS has killed more than 27 million people and more than 33 million people live
today with HIV.
b. In 2008,
i. 2.7 million people were newly infected with HIV and
ii. over 2 million died, including 300,000 children under age 15.
c. Most AIDS infections and deaths occur in nonindustrialized nations of southern Asia and sub-
Saharan Africa.
2. The AIDS virus usually attacks helper T cells impairing the
a. cell-mediated immune response and
b. humoral immune response,
c. opening the way for opportunistic infections.
3. AIDS patients typically die from
a. opportunistic infections and
b. cancers
c. that would normally be resisted by a person with a healthy immune system.
4. Until there is a vaccine or a cure, the best way to stop AIDS is to educate people about how the virus
is transmitted.
24.14 EVOLUTION CONNECTION: The rapid evolution of HIV complicates AIDS treatment
1. HIV mutates very quickly.
2. New strains are resistant to AIDS drugs.
3. Drug-resistant strains now infect new patients.
24.15 The immune system depends on our molecular fingerprints
1. The immune system normally reacts
a. only against nonself substances and
b. not against self.
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2. Transplanted organs may be rejected because the transplanted cells lack the unique “fingerprint” of
the patient’s self proteins, called major histocompatibility complex (MHC) molecules.
3. Donors are used that most closely match the patients’ tissues.
4. Transplants between identical twins do not typically have this problem.
Disorders of the Immune System
24.16 CONNECTION: Malfunction or failure of the immune system causes disease
1. Autoimmune diseases occur when the immune system turns against the body’s own molecules.
2. Examples of autoimmune diseases include
a. lupus,
b. rheumatoid arthritis,
c. insulin-dependent diabetes mellitus, and
d. multiple sclerosis.
3. Immunodeficiency diseases occur when an immune response is
a. defective or
b. absent.
4. The immune system may be weakened by
a. physical stress or
b. emotional stress.
c. Students are more likely to be sick during a week of exams.
24.17 CONNECTION: Allergies are overreactions to certain environmental antigens
1. Allergies are hypersensitive (exaggerated) responses to otherwise harmless antigens in our
surroundings.
2. Antigens that cause allergies are called allergens.
3. Allergic reactions typically occur
a. very rapidly and
b. in response to tiny amounts of an allergen.
4. Allergic reactions can occur in many parts of the body, including
a. nasal passages,
b. bronchi, and
c. skin.
5. The symptoms of an allergy result from a two-stage reaction.
a. The first stage, called sensitization, occurs when a person is first exposed to an
allergen.
b. The second stage begins when the person is exposed to the same allergen later.
i. The allergen binds to mast cells.
ii. Mast cells release histamine, causing irritation, itchy skin, and tears.
6. Antihistamines
a. interfere with histamine’s action,
b. provide temporary relief, but
c. often make people drowsy.
7. Anaphylactic shock
a. is an extreme life-threatening allergic reaction and
b. can be treated with injections of epinephrine.
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Chapter 16 vocab
auto- = self; -troph = food (autotroph: an organism that makes its own food)
chemo- = chemical; auto- = self; -troph = food (chemoautotroph: an organism that obtains both energy and
carbon from inorganic chemicals, making its own organic compounds from CO2 without using light energy);
hetero- = different (chemoheterotroph: an organism that obtains both
energy and carbon from organic molecules)
cyan- = dark blue (cyanobacteria: Photoautotrophic prokaryotes with plantlike, oxygen-generating
photosynthesis. These bacteria are sometimes called blue-green algae.)
endo- = inner, within (endospore: a thick-coated protective cell produced within a bacterial cell that can become
dormant to survive harsh environmental conditions; endotoxin: a poisonous component of the outer membrane of
gram-negative bacteria, released only when the bacteria die)
exo- = outside (exotoxin: a poisonous protein secreted by certain bacteria)
-gen = produce (methanogen: Archaea that produce methane as a metabolic waste product)
halo- = salt; -philos = loving (extreme halophile: a microorganism that lives in a highly saline
environment)
hetero- = different (chemoheterotroph: an organism that obtains both energy and carbon from
organic molecules)
photo- = light; auto- = self; -troph = food, nourish (photoautotroph: an organism that obtains
energy from sunlight and carbon from CO2)
-phyte = plant (gametophyte: the multicellular haploid form in the life cycle of organisms undergoing alternation
of generations)
pseudo- = false; -podium = foot (pseudopodium [plural, pseudopodia]: a temporary extension of an amoeboid
cell that functions in moving and feeding)
sym- = with, together; -bios = life (symbiosis: a close association between organisms of two or more species)
thermo- = heat; -philos = loving (extreme thermophile: a microorganism that thrives in a hot
environment)
