Chapter 27 practice problems/ Quiz problems

Question 1

Use the information in the following paragraph to answer the question.

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’s ability to survive in a human who is taking penicillin pills may be due to the presence of ________.

A. long polypeptides in the cell wall

B. peptidoglycan in the cell wall

C. gram-negative cell wall

D. lipopolysaccharides in the cytoplasm

Answer 1

C.

Question 2

In a bacterium that possesses antibiotic resistance and the potential to persist through very adverse conditions, such as freezing, drying, or high temperatures, DNA should be located within, or be part of, which structures?

A. nucleoid, fimbriae, and plasmids

B. plasmids, nucleoid, and endospore

C. endospore, fimbriae, and plasmids

D. fimbriae, nucleoid, and endospore

Answer 2

B

Question 3

If a bacterium regenerates from an endospore that did not possess any of the plasmids that were contained in its original parent cell, the regenerated bacterium will probably also lack ________.

A. a chromosome

B. water in its cytoplasm

C. a cell wall

D. antibiotic-resistant genes

Answer 3

D

Question 4

Termites eat wood, but many do not produce enzymes themselves that will digest the cellulose in the wood. Instead, some termites house a complex community of protozoa, bacteria, and archaea that could help digest the cellulose. Imagine an experiment that fed termites either wood only or wood and antibiotics, and then measured the amount of energy extracted from the wood. If both groups gained equal amounts of energy, which of the conclusions is the most logical?

A. We would conclude that the archaea contributed to digestion of cellulose and lignin.

B. We would conclude that none of the three groups were needed to digest cellulose and lignin.

C. We would conclude that the bacteria did not contribute to digestion of cellulose and lignin.

D. We would conclude that the protozoa contributed to digestion of cellulose and lignin.

Answer 4

C

Question 5

In a hypothetical situation, the genes for sex pilus construction and for tetracycline resistance are located on the same plasmid within a particular bacterium. If this bacterium readily performs conjugation involving a copy of this plasmid, then the result should be the ________.

A. rapid spread of tetracycline resistance to other bacteria in that habitat

B. temporary possession by this bacterium of a completely diploid genome

C. subsequent loss of tetracycline resistance from this bacterium

D. production of endospores among the bacterium’s progeny

Answer 5

A

Question 6

Which of the following is least associated with the others?

A. horizontal gene transfer

B. conjugation

C. binary fission

D. transformation

Answer 6

C

Question 7

Biologists sometimes divide living organisms into two groups: autotrophs and heterotrophs. These two groups differ in ________.

Question 8 options:

A. their electron acceptors

B. their mode of inheritance

C. the way that they generate ATP

D. their sources of carbon

Answer 7

D

Question 8

Which of the following traits do archaeans and bacteria share?

A. composition of the cell wall

B. lack of a nuclear envelope and the presence of circular chromosome

C. composition of the cell wall and lack of a nuclear envelope

D. presence of plasma membrane and composition of the cell wall

Answer 8

B

Question 9

Which of the following traits do archaeans and eukaryotes share?

A. presence of introns

B. sensitivity to streptomycin

C. presence of a nuclear envelope

D. presence of peptidoglycan in the cell wall

Answer 9

A

Question 10

Describe two adaptations that enable prokaryotes to survive in environments too harsh for other organisms.

Answer 10

Prokaryotes have an outer structure called a capsule (can be hard or soft) that protects them from elements and allows them to stick to surfaces, and also can produce endospores, which are simplified non-metabolic cells that are designed to withstand extreme environments.

Question 11

Contrast the cellular and DNA structures of prokaryotes and eukaryotes.

Answer 11

Prokaryotes do not have membrane enclosed DNA information (nuclei) like eukaryotes (but can store DNA in folds of their plasma membrane, although it is not fully enclosed). They also possess less DNA information than eukaryotic cells and it is arranged in a circular format. Prokaryotes also have additional independent DNA molecules called plasmids

Question 12

Suggest a hypothesis to explain why the thylakoid membranes of chloroplasts resemble those of cyanobacteria.

Answer 12

Endosymbiotic theory suggests that plastids (chloroplasts and other organelles that are similar in function) are a result of an ancestral photosynthetic prokaryote that was engulfed by an ancestral eukaryotic heterotroph. Evolutionary lineages suggest that plastids are more closely related to cyanobacteria as well

Question 13

Although rare on a per gene basis, new mutations can add considerable genetic variation to prokaryotic populations in each generation. Explain how this occurs.

Answer 13

Since prokaryotes have short generation times and replicate quickly via binary fission, rare mutations quickly become common in large populations, especially if they are advantageous for the organism.

Question 14

Distinguish between the three mechanisms by which bacteria can transfer DNA from one bacterial cell to another.

Answer 14

Transformation: when a bacterial cell envelops a foreign piece of DNA and incorporates it into its genome

Transduction: when a bacterial cell obtains genetic information via a viral infection of a bacteriophage which carried genetic information from one bacterial cell to another

Conjugation - when a one way transfer of genetic material is commenced between two bacterial organisms of the same species through a structure called a pili

Question 15

In a rapidly changing environment, which bacterial population would likely be more successful: one that has individuals capable of conjugation or one that does not? Explain.

Answer 15

The individuals with conjugation capabilities would be more successful, given that they can pass advantageous adaptive genes in between one another which makes it more likely that novel genetic mutations can arise through new gene combinations

Question 16

If a nonpathogenic bacterium were to acquire resistance to antibiotics, could this strain pose a health risk to people? In general, how does DNA transfer among bacteria affect the spread of resistance genes?

Answer 16

Yes, this could indirectly pose a health risk to people, as nonpathogenic bacteria can pass resistance genes through genetic recombination strategies to pathogenic bacteria

DNA transfer allows the spread of resistance to grow exponentially

Question 17

Distinguish between the four major modes of nutrition, noting which are unique to prokaryotes.

Answer 17

Photoautotroph - which receives energy from sunlight (photosynthesis) and converts inorganic molecules into a carbon source

Photoheterotroph - which receives energy from sunlight (photosynthesis) but derives carbon from organic sources like glucose

Chemoautotrophs - which receive energy from chemical sources and convert inorganic molecules into a carbon source (unique only to prokaryotes)

Chemoheterotrophs - receive energy from chemical sources and need organic materials (like glucose) for a carbon source

Question 18

A bacterium requires only the amino acid methionine as an organic nutrient and lives in lightless
caves. What mode of nutrition does it employ? Explain.

Answer 18

Chemoheterotrophy - since it needs an organic nutrient as a carbon source, and derives energy from chemicals (does not need sunlight for energy)

Question 19

Describe what you might eat for a typical meal if humans, like cyanobacteria, could fix nitrogen.

Answer 19

If humans could fix nitrogen, we would be able to synthesize proteins using atmospheric Nitrogen instead of eating high-protein foods like meats and dairy products. We would still need to consume carbs as a carbon source, and essential minerals.

Question 20

Explain how molecular systematics and metagenomics have contributed to our understanding of the phylogeny and evolution or prokaryotes.

Answer 20

Systematics and genomics have found a new classification of microorganisms that was originally classified as bacteria: Archaea, as they seem to possess characteristics of both prokaryotes and eukaryotes and don’t necessarily fall into either category.

Research has also found that although prokaryotes do not sexually reproduce, they still create environments of genetic variation by horizontal gene transfer mechanisms for genetic recombination, and their genomic sequences also mutate

Question 21

Explain how prokaryotes, though small, can be considered giants in their collective impact on Earth
and its life

Answer 21

They are large in number and diverse, and have metabolic abilities that enable them to help ecosystems by decomposing wastes, recycling chemicals, and affecting concentrations of nutrients available to other organisms.

They also benefit animal species by playing the role of mutualistic symbionts, and hurt animal species by being parasitic symbionts as well

Question 22

Identify at least two ways that prokaryotes have affected you positively today.

Answer 22

1. fermented foods
2. gut microbiota
3. decomposition of sewage
4. production of antibiotics

Question 23

How might a sudden and dramatic change in your diet affect the diversity of prokaryotic species that live in your digestive tract?

Answer 23

Prokaryotes in the digestive tract compete for nutrients from the food we eat, and if there is a dramatic change of diet, different prokaryotes that prefer those nutrients in that change may proliferate and cause an imbalance.