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Exam 27: Bacteria and Archaea

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Question 21

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Which statement about bacterial cell walls is false?

A) Bacterial cell walls differ in molecular composition from plant cell walls.
B) Cell walls prevent cells from bursting in hypotonic environments.
C) Cell walls prevent cells from dying in hypertonic conditions.
D) Bacterial cell walls are similar in function to the cell walls of many protists, fungi, and plants.
E) Cell walls provide the cell with a degree of physical protection from the environment.

F) C) and D)
G) A) and E)

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Question 22

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Bacteria can infect fish both externally and internally. Which is the most likely point of entry of bacteria that will cause an internal infection?

A) gills
B) skin along the dorsal side of the fish
C) skin along the ventral side of the fish
D) tail
E) fins

F) A) and E)
G) A) and B)

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Question 23

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Use the following information to answer the questions below. Nitrogenase, the enzyme that catalyzes nitrogen fixation, is inhibited whenever free O₂ reaches a critical concentration. Consequently, nitrogen fixation cannot occur in cells wherein photosynthesis produces free O₂. Consider the colonial aquatic cyanobacterium, Anabaena, whose heterocytes are described as having "…a thickened cell wall that restricts entry of O₂ produced by neighbouring cells. Intracellular connections allow heterocysts to transport fixed nitrogen to neighbouring cells in exchange for carbohydrates." -Which two questions below arise from a careful reading of this quotation, and are most important for understanding how N₂ enters heterocysts, and how O₂ is kept out of heterocysts? 1. If carbohydrates can enter the heterocysts from neighbouring cells via the "intracellular connections," how is it that O₂ doesn't also enter via this route? 2. If the cell walls of Anabaena's photosynthetic cells are permeable to O₂ and CO₂, are they also permeable to N₂? 3. If the nuclei of the photosynthetic cells contain the genes that code for nitrogen fixation, how can these cells fail to perform nitrogen fixation? 4. If the nuclei of the heterocysts contain the genes that code for photosynthesis, how can these cells fail to perform photosynthesis? 5. If the cell walls of Anabaena's heterocysts are permeable to N₂, how is it that N₂ doesn't diffuse out of the heterocysts before it can be fixed? 6. If the thick cell walls of the heterocysts exclude entry of oxygen gas, how is it that they don't also exclude the entry of nitrogen gas?

Although not present in all bacteria, this cell covering often enables cells that possess it to resist the defences of host organisms, especially their phagocytic cells.

Which of the following traits do archaeans and bacteria share? 1. composition of the cell wall 2. presence of plasma membrane 3. lack of a nuclear envelope 4. identical rRNA sequences

Jams, jellies, preserves, honey, and other foodstuffs with high sugar content hardly ever become contaminated by bacteria, even when the food containers are left open at room temperature. This is because bacteria that encounter such an environment

E. coli cells typically make most of their ATP by metabolizing glucose. Under the conditions of this experiment, what should be true of E. coli's generation time (especially early in the course of the experiment, but less so later on) ?

The thermoacidophile Sulfolobus acidocaldarius lacks peptidoglycan, but still possesses a cell wall. What is likely to be true of this species? 1. It is a bacterium. 2. It is an archaean. 3. The optimal pH of its enzymes will lie above pH 7. 4. The optimal pH of its enzymes will lie below pH 7. 5. It could inhabit certain hydrothermal springs. 6. It could inhabit alkaline hot springs.

Which of the following statements is not true?

The termite gut protist, Mixotricha paradoxa, has at least two kinds of bacteria attached to its outer surface. One kind is a spirochete that propels its host through the termite gut. A second type of bacteria synthesizes ATP, some of which is used by the spirochetes. The locomotion provided by the spirochetes introduces the ATP-producing bacteria to new food sources. Which term(s) is (are) applicable to the relationship between the two kinds of bacteria? 1. mutualism 2. parasitism 3. symbiosis 4. metabolic cooperation

Mycoplasmas are bacteria that lack cell walls. On the basis of this structural feature, which statement concerning mycoplasmas should be true?

Broad-spectrum antibiotics inhibit the growth of most intestinal bacteria. Consequently, assuming that nothing is done to counter the reduction of intestinal bacteria, a hospital patient who is receiving broad-spectrum antibiotics is most likely to become

Use the information in the following paragraph to answer the next few questions. A hypothetical bacterium swims among human intestinal contents until it finds a suitable location on the intestinal lining. It adheres to the intestinal lining using a feature that also protects it from phagocytes, bacteriophages, and dehydration. Fecal matter from a human in whose intestine this bacterium lives can spread the bacterium, even after being mixed with water and boiled. The bacterium is not susceptible to the penicillin family of antibiotics. It contains no plasmids and relatively little peptidoglycan. -Some of the proteins that allow this bacterium to swim are related (in an evolutionary sense) to proteins that

We have overwhelming evidence that Bacteria and Archaea are masters of adaptation. Which key characteristic enables these prokaryotes to occupy almost every habitat on earth?

If archaeans are more closely related to eukaryotes than to bacteria, then which of the following is a reasonable prediction?

Use the information in the following paragraph to answer the next few questions. A hypothetical bacterium swims among human intestinal contents until it finds a suitable location on the intestinal lining. It adheres to the intestinal lining using a feature that also protects it from phagocytes, bacteriophages, and dehydration. Fecal matter from a human in whose intestine this bacterium lives can spread the bacterium, even after being mixed with water and boiled. The bacterium is not susceptible to the penicillin family of antibiotics. It contains no plasmids and relatively little peptidoglycan. -This bacterium derives nutrition by digesting human intestinal contents (in other words, food) . Thus, this bacterium should be an

Plantlike photosynthesis that releases O₂ occurs in

Hershey and Chase performed an elegant experiment that convinced most biologists that DNA, rather than protein, was the genetic material. This experiment subjected bacteria to the same gene transfer mechanism as occurs in

Use the information in the following paragraph to answer the next few questions. A hypothetical bacterium swims among human intestinal contents until it finds a suitable location on the intestinal lining. It adheres to the intestinal lining using a feature that also protects it from phagocytes, bacteriophages, and dehydration. Fecal matter from a human in whose intestine this bacterium lives can spread the bacterium, even after being mixed with water and boiled. The bacterium is not susceptible to the penicillin family of antibiotics. It contains no plasmids and relatively little peptidoglycan. -The cell also lacks F factors and F plasmids. Upon its death, this bacterium should be able to participate in

All of the following are potential causes that may have contributed to the introduction and spread of the infection in the two tanks, with the exception of