BIO 1414 Exam 2 Ch: 21, 22, 23

Prions are responsible for variant Creutzfeldt- Jakob Disease, which has resulted in over 100 human deaths in Great Britain during the last 10 years. How do humans obtain this disease?

This prion-based disease is transmitted through human consumption of infected meat.

Think about the conditions (temperature, light, pressure, and organic and inorganic materials) that you may find in a deep-sea hydrothermal vent. What type of prokaryotes, in terms of their metabolic needs (autotrophs, phototrophs, chemotrophs, etc.), would you expect to find there?

In a deep-sea hydrothermal vent, there is no light, so prokaryotes would be chemotrophs instead of phototrophs. The source of carbon would be carbon dioxide dissolved in the ocean, so they would be autotrophs. There is not a lot of organic material in the ocean, so prokaryotes would probably use inorganic sources, thus they would be chemolitotrophs. The temperatures are very high in the hydrothermal vent, so the prokaryotes would be thermophilic.

Influenza virus is packaged in a viral envelope that fuses with the plasma membrane. This way, the virus can exit the host cell without killing it. What advantage does the virus gain by keeping the host cell alive?

The host cell can continue to make new virus particles

Conjugation between two Paramecia produces ________ total daughter cells. a. 2 b. 4 c. 8 d. 16

c. 8

Which of the following statements is false? a. In the lytic cycle, new phage are produced and released into the environment. b. In the lysogenic cycle, phage DNA is incorporated into the host genome. c. An environmental stressor can cause the phage to initiate the lysogenic cycle. d. Cell lysis only occurs in the lytic cycle.

c. An environmental stressor can cause the phage to initiate the lysogenic cycle.

Alternation of generations describes which of the following? a. The haploid form can be multicellular; the diploid form is unicellular. b. The haploid form is unicellular; the diploid form can be multicellular. c. Both the haploid and diploid forms can be multicellular. d. Neither the haploid nor the diploid forms can be multicellular.

c. Both the haploid and diploid forms can be multicellular.

Which of the following is not associated with prions? a. replicating shapes b. mad cow disease c. DNA d. toxic proteins

c. DNA

Which characteristic is shared by prokaryotes and eukaryotes? a. cytoskeleton b. nuclear envelope c. DNA-based genome d. mitochondria

c. DNA-based genome

Which transcriptase? statement is true of reverse a. It is a nucleic acid. b. It infects cells. c. It transcribes RNA to make DNA. d. It is a lipid.

c. It transcribes RNA to make DNA.

Which of the following statements about Paramecium sexual reproduction is false? a. The macronuclei are derived from micronuclei. b. Both mitosis and meiosis occur during sexual reproduction. c. The conjugate pair swaps macronuclei. d. Each parent produces four daughter cells.

c. The conjugate pair swaps macronuclei.

Which of the following statements about the Laminaria life cycle is false? a. 1n zoospores form in the sporangia. b. The sporophyte is the 2n plant. c. The gametophyte is diploid. d. Both the gametophyte and sporophyte stages are multicellular.

c. The gametophyte is diploid.

Which of the following is NOT used to treat active viral disease? a. vaccines b. antiviral drugs c. antibiotics d. phage therapy

c. antibiotics

Pseudopeptidoglycan is a characteristic of the walls of ________. a. eukaryotic cells b. bacterial prokaryotic cells c. archaean prokaryotic cells d. bacterial and archaean prokaryotic cells

c. archaean prokaryotic cells

Prokaryotes that obtain their energy from chemical compounds are called _____. a. phototrophs b. auxotrophs c. chemotrophs d. lithotrophs

c. chemotrophs

A disease that is constantly present in a population is called _____. a. pandemic b. epidemic c. endemic d. re-emerging

c. endemic

Mitochondria most likely evolved by _____________. a. a photosynthetic cyanobacterium b. cytoskeletal elements c. endosymbiosis d. membrane proliferation

c. endosymbiosis

Which protist group exhibits mitochondrial remnants with reduced functionality? a. slime molds b. diatoms c. parabasalids d. dinoflagellates

c. parabasalids

Which of these occurs through symbiotic nitrogen fixation? a. The plant benefits from using an endless source of nitrogen. b. The soil benefits from being naturally fertilized. c. Bacteria benefit from using photosynthates from the plant. d. All of the above occur.

d. All of the above occur.

Which of the statements about biofilms is incorrect? a. Biofilms are considered responsible for diseases such as cystic fibrosis. b. Biofilms produce dental plaque, and colonize catheters and prostheses. c. Biofilms colonize open wounds and burned tissue. d. All statements are incorrect.

d. All statements are incorrect.

What genus of protists appears to contradict the statement that unicellularity restricts cell size? a. Dictyostelium b. Ulva c. Plasmodium d. Caulerpa

d. Caulerpa

Which of the following statements about virus structure is true? a. All viruses are encased in a viral membrane. b. The capsomere is made up of small protein subunits called capsids. c. DNA is the genetic material in all viruses. d. Glycoproteins help the virus attach to the host cell.

d. Glycoproteins help the virus attach to the host cell.

Which statement is not true of viral replication? a. lysogenic cycle kills the host cell. b.There are six basic steps in the viral replication cycle. c. Viral replication does not affect host cell function. d. Newly released virions can infect adjacent cells.

d. Newly released virions can infect adjacent cells.

Which of the following statements about the nitrogen cycle is false? a. Nitrogen fixing bacteria exist on the root nodules of legumes and in the soil. b. Denitrifying bacteria convert nitrates (NO3-) into nitrogen gas (N2). c. Ammonification is the process by which ammonium ion (NH4+) is released from decomposing organic compounds. d. Nitrification is the process by which nitrites (NO2-) are converted to ammonium ion (NH4+).

d. Nitrification is the process by which nitrites (NO2-) are converted to ammonium ion (NH4+).

Microbial mats __________. a. are the earliest forms of life on Earth b. obtained their energy and food from hydrothermal vents c. are multi-layered sheet of prokaryotes including mostly bacteria but also archaea d. all of the above

d. all of the above

A bacteriophage can infect ________. a. the lungs b. viruses c. prions d. bacteria

d. bacteria

Which of the following consist of prokaryotic cells? a. bacteria and fungi b. archaea and fungi c. protists and animals d. bacteria and archaea

d. bacteria and archaea

The viral ________ plays a role in attaching a virion to the host cell. a. core b. capsid c. envelope d. both b and c

d. both b and c

Which of these protists is believed to have evolved following a secondary endosymbiosis? a. green algae b. cyanobacteria c. red algae d. chlorarachniophytes

d. chlorarachniophytes

Oncogenic virus cores can be_______. a. RNA b. DNA c. neither RNA nor DNA d. either RNA or DNA

d. either RNA or DNA

What event is thought to have contributed to the evolution of eukaryotes? a. global warming b. glaciation c. volcanic activity d. oxygenation of the atmosphere

d. oxygenation of the atmosphere

Protists that have a pellicle are surrounded by ______________. a. silica dioxide b. calcium carbonate c. carbohydrates d. proteins

d. proteins

Vaccines_______. a. are similar to viroids b. are only needed once c. kill viruses d. stimulate an immune response

d. stimulate an immune response

Viruses_______. a. all have a round shape b. cannot have a long shape c. do not maintain any shape d. vary in shape

d. vary in shape

Synthetic compounds found in an organism but not normally produced or expected to be present in that organism are called _____. a. pesticides b. bioremediators c. recalcitrant compounds d. xenobiotics

d. xenobiotics

Mention three differences between bacteria and archaea.

A possible answer is: Bacteria contain peptidoglycan in the cell wall; archaea do not. The cell membrane in bacteria is a lipid bilayer; in archaea, it can be a lipid bilayer or a monolayer. Bacteria contain fatty acids on the cell membrane, whereas archaea contain phytanyl.

What evidence is there that mitochondria were incorporated into the ancestral eukaryotic cell before chloroplasts?

All eukaryotic cells have mitochondria, but not all eukaryotic cells have chloroplasts.

Explain the reason why the imprudent and excessive use of antibiotics has resulted in a major global problem.

Antibiotics kill bacteria that are sensitive to them; thus, only the resistant ones will survive. These resistant bacteria will reproduce, and therefore, after a while, there will be only resistant bacteria.

Describe briefly how you would detect the presence of a non-culturable prokaryote in an environmental sample.

As the organisms are non-culturable, the presence could be detected through molecular techniques, such as PCR.

Why do scientists believe that the first organisms on Earth were extremophiles?

Because the environmental conditions on Earth were extreme: high temperatures, lack of oxygen, high radiation, and the like.

Explain the statement that both types, bacteria and archaea, have the same basic structures, but built from different chemical components.

Both bacteria and archaea have cell membranes and they both contain a hydrophobic portion. In the case of bacteria, it is a fatty acid; in the case of archaea, it is a hydrocarbon (phytanyl). Both bacteria and archaea have a cell wall that protects them. In the case of bacteria, it is composed of peptidoglycan, whereas in the case of archaea, it is pseudopeptidoglycan, polysaccharides, glycoproteins, or pure protein. Bacterial and archaeal flagella also differ in their chemical structure.

Why might a light-sensing eyespot be ineffective for an obligate saprobe? Suggest an alternative organ for a saprobic protist.

By definition, an obligate saprobe lacks the ability to perform photosynthesis, so it cannot directly obtain nutrition by searching for light. Instead, a chemotactic mechanism that senses the odors released during decay might be a more effective sensing organ for a saprobe.

Researchers have discovered that washing spinach with water several times does not prevent foodborne diseases due to E. coli. How can you explain this fact?

E. coli colonizes the surface of the leaf, forming a biofilm that is more difficult to remove than free (planktonic) cells. Additionally, bacteria can be taken up in the water that plants are grown in, thereby entering the plant tissues rather than simply residing on the leaf surface.

Although plant viruses cannot infect humans, what are some of the ways in which they affect humans?

Plant viruses infect crops, causing crop damage and failure, and considerable economic losses.

How does killing Anopheles mosquitoes affect the Plasmodium protists?

Plasmodium parasites infect humans and cause malaria. However, they must complete part of their life cycle within Anopheles mosquitoes, and they can only infect humans via the bite wound of a mosquito. If the mosquito population is decreased, then fewer Plasmodium would be able to develop and infect humans, thereby reducing the incidence of human infections with this parasite.

Why is immunization after being bitten by a rabid animal so effective and why aren't people vaccinated for rabies like dogs and cats are?

Rabies vaccine works after a bite because it takes week for the virus to travel from the site of the bite to the central nervous system, where the most severe symptoms of the disease occur. Adults are not routinely vaccinated for rabies for two reasons: first, because the routine vaccination of domestic animals makes it unlikely that humans will contract rabies from an animal bite; second, if one is bitten by a wild animal or a domestic animal that one cannot confirm has been immunized, there is still time to give the vaccine and avoid the often fatal consequences of the disease.

One of the first and most important targets for drugs to fight infection with HIV (a retrovirus) is the reverse transcriptase enzyme. Why?

Reversetranscriptaseisneededto make more HIV-1 viruses, so targeting the reverse transcriptase enzyme may be a way to inhibit the replicationof the virus. Importantly, by targeting reverse transcriptase, we do little harm to the host cell, since host cells do not make reverse transcriptase. Thus, we can specifically attack the virus and not the host cell when we use reverse transcriptase inhibitors.

Compared to free-floating bacteria, bacteria in biofilms often show increased resistance to antibiotics and detergents. Why do you think this might be the case?

The extracellular matrix and outer layer of cells protects the inner bacteria. The close proximity of cells also facilitates lateral gene transfer, a process by which genes such as antibiotic resistance genes are transferred from one bacterium to another. And even if lateral gene transfer does not occur, one bacterium that produces an exo-enzyme that destroys antibiotic may save neighboring bacteria.

Without treatment, why does African sleeping sickness invariably lead to death?

The trypanosomes that cause this disease are capable of expressing a glycoprotein coat with a different molecular structure with each generation. Because the immune system must respond to specific antigens to raise a meaningful defense, the changing nature of trypanosome antigens prevents the immune system from ever clearing this infection. Massive trypanosome infection eventually leads to host organ failure and death.

Why can't dogs catch the measles?

The virus can't attach to dog cells, because dog cells do not express the receptors for the virus and/or there is no cell within the dog that is permissive for viral replication.

How are viroids like viruses?

They both replicate in a cell, and they both contain nucleic acid.

The chlorophyte (green algae) genera Ulva and Caulerpa both have macroscopic leaf-like and stem-like structures, but only Ulva species are considered truly multicellular. Explain why.

Unlike Ulva, protists in the genus Caulerpa actually are large, multinucleate, single cells. Because these organisms undergo mitosis without cytokinesis and lack cytoplasmic divisions, they cannot be considered truly multicellular.

The first electron micrograph of a virus (tobacco mosaic virus) was produced in 1939. Before that time, how did scientists know that viruses existed if they could not see them? (Hint: Early scientists called viruses "filterable agents.")

Viruses pass through filters that eliminated all bacteria that were visible in the light microscopes at the time. As the bacteria-free filtrate could still cause infections when given to a healthy organism, this observation demonstrated the existence of very small infectious agents. These agents were later shown to be unrelated to bacteria and were classified as viruses.

Which of these statements is true? a. An antibiotic is any substance produced by a organism that is antagonistic to the growth of prokaryotes. b. An antibiotic is any substance produced by a prokaryote that is antagonistic to the growth of other viruses. c. An antibiotic is any substance produced by a prokaryote that is antagonistic to the growth of eukaryotic cells. d. An antibiotic is any substance produced by a prokaryote that prevents growth of the same prokaryote.

a. An antibiotic is any substance produced by a organism that is antagonistic to the growth of prokaryotes.

Which of the following statements is true? a. Gram-positive bacteria have a single cell wall anchored to the cell membrane by lipoteichoic acid. b. Porins allow entry of substances into both Gram-positive and Gram-negative bacteria. c. The cell wall of Gram-negative bacteria is thick, and the cell wall of Gram-positive bacteria is thin. d. Gram-negative bacteria have a cell wall made of peptidoglycan, whereas Gram-positive bacteria have a cell wall made of lipoteichoic acid.

a. Gram-positive bacteria have a single cell wall anchored to the cell membrane by lipoteichoic acid.

Which statement is true of viroids? a. They are single-stranded RNA particles. b. They reproduce only outside of the cell. c. They produce proteins. d. They affect both plants and animals.

a. They are single-stranded RNA particles.

Which is true of DNA viruses? a. They use the host cell's machinery to produce new copies of their genome. b. They all have envelopes. c. They are the only kind of viruses that can cause cancer. d. They are not important plant pathogens.

a. They use the host cell's machinery to produce new copies of their genome.

Halophiles are organisms that require________. a. a salt concentration of at least 0.2 M b. high sugar concentration c. the addition of halogens d. all of the above

a. a salt concentration of at least 0.2 M

Ammonification is the process by which _____. a. ammonia is released during the decomposition of nitrogen-containing organic compounds b. ammonium is converted to nitrite and nitrate in soils c. nitrate from soil is transformed to gaseous nitrogen compounds such as NO, N2O, and N2 d. gaseous nitrogen is fixed to yield ammonia

a. ammonia is released during the decomposition of nitrogen-containing organic compounds

The first organisms that oxygenated the atmosphere were a. cyanobacteria b. phototrophic organisms c. anaerobic organisms d. all of the above

a. cyanobacteria

What is the function of the raphe in diatoms? a. locomotion b. defense c. capturing food d. photosynthesis

a. locomotion

An example of carbon fixation is _____________. a. photosynthesis b. decomposition c. phagocytosis d. parasitism

a. photosynthesis

The first forms of life on Earth were thought to be_________. a. single-celled plants b. prokaryotes c. insects d. large animals such as dinosaurs

a. single-celled plants

Prokaryotes stain as Gram-positive or Gram-negative because of differences in the cell _______. a. wall b. cytoplasm c. nucleus d. chromosome

a. wall

Which statement is true of viral replication? a. In the process of apoptosis, the cell survives. b. During attachment, the virus attaches at specific sites on the cell surface. c. The viral capsid helps the host cell produce more copies of the viral genome. d. mRNA works outside of the host cell to produce enzymes and proteins.

b. During attachment, the virus attaches at specific sites on the cell surface.

The lipopolysaccharide layer (LPS) is a characteristic of the wall of ________. a. archaean cells b. Gram-negative bacteria c. bacterial prokaryotic cells d. eukaryotic cells

b. Gram-negative bacteria

Which parasitic protist evades the host immune system by altering its surface proteins with each generation? a. Paramecium caudatum b. Trypanosoma brucei c. Plasmodium falciparum d. Phytophthora infestans

b. Trypanosoma brucei

Which statement is true? a. A virion contains DNA and RNA. b. Viruses are acellular. c. Viruses replicate outside of the cell. d. Most viruses are easily visualized with a light microscope.

b. Viruses are acellular.

Which of these locomotor organs would likely be the shortest? a. a flagellum b. a cilium c. an extended pseudopod d. a pellicle

b. a cilium

Organisms most likely to be found in extreme environments are ________. a. fungi b. bacteria c. viruses d. archaea

b. bacteria

Which of the following elements is not a micronutrient? a. boron b. calcium c. chromium d. manganese

b. calcium

The presence of a membrane-enclosed nucleus is a characteristic of ________. a. prokaryotic cells b. eukaryotic cells c. all cells d. viruses

b. eukaryotic cells

The cell wall is ________. a. interior to the cell membrane b. exterior to the cell membrane c. a part of the cell membrane d. interior or exterior, depending on the particular cell

b. exterior to the cell membrane

Protists with the capabilities to perform photosynthesis and to absorb nutrients from dead organisms are called ______________. a. photoautotrophs b. mixotrophs c. saprobes d. heterotrophs

b. mixotrophs

Plants use carbon dioxide from the air and are therefore called _____. a. consumers b. producers c. decomposer d. carbon fixers

b. producers

Bioremediation includes _____. a. the use of prokaryotes that can fix nitrogen b. the use of prokaryotes to clean up pollutants c. the use of prokaryotes as natural fertilizers d. All of the above

b. the use of prokaryotes to clean up pollutants