Question 1

If scientists could quantify all the bacterial and human cells on Earth, they would find that there are far more human cells.

Accepted Answer

According to recent estimates, the total number of bacterial cells on Earth is roughly 5x10^30, while the total number of human cells is estimated to be around 3x10^13. Therefore, there are far more bacterial cells on Earth than human cells.

Question 2

What is one advantage of fermentation over cellular respiration in certain environments?

Accepted Answer

Fermentation does not require oxygen, making it advantageous in environments where oxygen is limited or absent. In contrast, cellular respiration requires oxygen for maximum energy production.

Question 3

Which is NOT a difference between anoxygenic photosynthetic organisms and oxygenic photosynthetic organisms?

Accepted Answer

Both anoxygenic and oxygenic photosynthetic organisms need a source of carbon to perform photosynthesis. The differences between the two lie in the source of electrons, type of chlorophyll, number of photosystems, and wavelengths at which light is absorbed.

Question 4

An organism that acquires energy from the sun and uses C₆H₁₂O₆ as a carbon source would be classified as a:

Accepted Answer

A photoheterotroph acquires energy from the sun (photo-) and uses organic compounds like C6H12O6 as a carbon source (heterotroph).

Question 5

A marine biologist descends in a submarine through the waters of the Black Sea. The top hundred meters or so are well oxygenated, but deeper waters are rich in hydrogen sulfide. What biological metabolisms can explain the distribution of H₂S in the Black Sea?

Accepted Answer

The answer of A marine biologist descends in a submarine...

Question 6

During oxygenic photosynthesis, water is _____ and loses electrons. (i.e., it serves as an electron donor).

Accepted Answer

During oxygenic photosynthesis, water is oxidized and loses electrons, which are then used to reduce carbon dioxide and produce carbohydrates.

Question 7

A researcher wants to determine if a unicellular organism he discovered is an autotroph or a heterotroph. He radioactively labels the carbon in CO₂ and C₆H₁₂O₆, and exposes one culture of his organism to the labeled CO₂ and another culture to the labeled C₆H₁₂O₆. What would happen if his organism is an autotroph?

Accepted Answer

If the organism is an autotroph, it will use the labeled carbon from CO₂ to produce carbohydrates through photosynthesis. Therefore, labeled carbon will be seen in the carbohydrates of the culture exposed to CO₂. However, if the organism is a heterotroph, it will break down the labeled carbon-containing compounds from C₆H₁₂O₆ to produce energy and cellular materials, leading to labeled carbon in the carbohydrates of neither culture.

Question 8

Fermentation yields an amount of energy equivalent to respiration because both processes achieve full oxidation of carbon compounds to CO₂.

Accepted Answer

Fermentation yields much less energy than respiration because it does not fully oxidize carbon compounds to carbon dioxide; instead, it partially breaks down glucose without using oxygen, resulting in less ATP production compared to aerobic respiration.

Question 9

A researcher is studying a specific strain of bacteria. In one of her cultures, she notices that the bacteria are antibiotic-resistant. As there are no genes in the chromosome that could confer antibiotic-resistance in these bacteria, the researcher assumes this is the result of a spontaneous mutation. What is another possible explanation?

Accepted Answer

Plasmids are small, circular pieces of DNA that are separate from the bacterial chromosome and can often carry genes that confer antibiotic resistance. This is a common mechanism for the spread of antibiotic resistance in bacteria.

Question 10

A researcher is comparing the sequences of genes encoding cell wall proteins in archaeons with those coding cell wall proteins in bacteria. How similar do you expect these sequences will be?

Accepted Answer

Archaeon cell walls are not composed of peptidoglycan, which is a characteristic feature of bacterial cell walls. Therefore, the sequences of genes encoding cell wall proteins in archaeons would be dissimilar to those in bacteria.

Question 11

The text discusses the metabolisms that link the N and S cycles to Earth's biological carbon cycle. Can you outline ways in which the carbon cycle might also be linked to the biological cycling of iron?

Accepted Answer

The answer of The text discusses the metabolisms that link...

Question 12

If biologists could quantify all the bacterial and human cells within the human body, they would find that there are far more human cells.

Accepted Answer

Current estimates suggest that there are roughly the same number of bacterial cells and human cells within the human body. However, bacterial cells tend to be much smaller than human cells, so the total mass of bacteria in the body is believed to be much less than the total mass of human cells.

Question 13

Autotrophs produce carbohydrates by reducing CO₂, whereas heterotrophs synthesize carbohydrates by ingesting smaller preformed organic compounds like glucose.

Accepted Answer

Autotrophs are able to produce their own carbohydrates through photosynthesis or chemosynthesis, which involves the reduction of CO₂. Heterotrophs, on the other hand, need to obtain preformed organic compounds like glucose through ingestion or absorption in order to synthesize their carbohydrates.

Question 14

A doctor is treating a patient for an apparent bacterial infection. She prescribes antibiotics that target either the peptidoglycan in bacterial cell walls or the bacterial translational machinery. To her surprise, this treatment does not work. Why might this treatment be ineffective?

Accepted Answer

The most likely reason for the antibiotic treatment to be ineffective is that the bacterium has developed resistance to the antibiotics. This is a common problem due to the overuse and misuse of antibiotics, which can lead to the evolution of antibiotic-resistant strains of bacteria. Options B and C are unlikely because chitin and cellulose are not commonly found in bacterial cell walls.

Question 15

All bacteria are unicellular.

Accepted Answer

Some bacteria, such as those in the genus Streptomyces, form complex multicellular structures or filaments.

Question 16

Imagine you are talking to your friend who is very excited because he has just transduced his first batch of bacteria in the laboratory. What does this mean?

Accepted Answer

Transduction is the method of introducing a gene of interest into bacterial cells using viruses called bacteriophages. Therefore, if someone has transduced their bacteria, it means they have introduced a gene of interest into the bacteria using a bacteriophage.

Question 17

Imagine that a scientist is able to reverse the principles of diffusion, such that molecules preferentially move from regions of low concentrations to regions of high concentrations. How would this affect the morphology of bacteria?

Accepted Answer

If molecules preferentially moved from regions of low concentrations to regions of high concentrations, bacteria would have to actively transport molecules across the cell membrane to maintain a high concentration inside the cell. This would potentially allow for bacteria to grow larger. Additionally, bacteria would have to prevent the diffusion of molecules out of the cell, potentially allowing for bacteria to grow wider. Thus, both options B and C are likely, resulting in answer choice D being the best choice.

Question 18

Bacteria contain neither organelle-associated membranes nor a cell membrane.

Accepted Answer

Bacteria do contain a cell membrane, also known as a plasma membrane, which helps to maintain the integrity of the cell and selectively transport nutrients and waste. However, they do not contain membrane-bound organelles, such as a nucleus or mitochondria.

Question 19

Photoheterotrophs rely on sunlight and organic molecules obtained from the environment.

Accepted Answer

Photoheterotrophs use light for energy, but they cannot use carbon dioxide as their sole carbon source, instead relying on organic compounds from the environment.

Question 20

An organism that oxidizes H₂S to gain energy and utilizes CO₂ as a carbon source (to generate carbohydrates) would be classified as a:

Accepted Answer

The organism in question gains energy from the oxidation of H₂S, suggesting that it obtains energy from inorganic sources (chemo-). Additionally, it utilizes CO₂ as a carbon source (autotroph), indicating that it can generate its own carbohydrates. Therefore, the correct classification for this organism is a chemoautotroph.

Quiz 26: Bacteria and Archaea

If scientists could quantify all the bacterial and human cells on Earth, they would find that there are far more human cells.

What is one advantage of fermentation over cellular respiration in certain environments?

Which is NOT a difference between anoxygenic photosynthetic organisms and oxygenic photosynthetic organisms?

An organism that acquires energy from the sun and uses C₆H₁₂O₆ as a carbon source would be classified as a:

A marine biologist descends in a submarine through the waters of the Black Sea. The top hundred meters or so are well oxygenated, but deeper waters are rich in hydrogen sulfide. What biological metabolisms can explain the distribution of H₂S in the Black Sea?

During oxygenic photosynthesis, water is _____ and loses electrons. (i.e., it serves as an electron donor) .

Fermentation yields an amount of energy equivalent to respiration because both processes achieve full oxidation of carbon compounds to CO₂.

A researcher is comparing the sequences of genes encoding cell wall proteins in archaeons with those coding cell wall proteins in bacteria. How similar do you expect these sequences will be?

The text discusses the metabolisms that link the N and S cycles to Earth's biological carbon cycle. Can you outline ways in which the carbon cycle might also be linked to the biological cycling of iron?

If biologists could quantify all the bacterial and human cells within the human body, they would find that there are far more human cells.

Autotrophs produce carbohydrates by reducing CO₂, whereas heterotrophs synthesize carbohydrates by ingesting smaller preformed organic compounds like glucose.

A doctor is treating a patient for an apparent bacterial infection. She prescribes antibiotics that target either the peptidoglycan in bacterial cell walls or the bacterial translational machinery. To her surprise, this treatment does not work. Why might this treatment be ineffective?

All bacteria are unicellular.

Imagine you are talking to your friend who is very excited because he has just transduced his first batch of bacteria in the laboratory. What does this mean?

Imagine that a scientist is able to reverse the principles of diffusion, such that molecules preferentially move from regions of low concentrations to regions of high concentrations. How would this affect the morphology of bacteria?

Bacteria contain neither organelle-associated membranes nor a cell membrane.

Photoheterotrophs rely on sunlight and organic molecules obtained from the environment.

An organism that oxidizes H₂S to gain energy and utilizes CO₂ as a carbon source (to generate carbohydrates) would be classified as a:

Quiz 26: Bacteria and Archaea

If scientists could quantify all the bacterial and human cells on Earth, they would find that there are far more human cells.

What is one advantage of fermentation over cellular respiration in certain environments?

Which is NOT a difference between anoxygenic photosynthetic organisms and oxygenic photosynthetic organisms?

An organism that acquires energy from the sun and uses C6H12O6 as a carbon source would be classified as a:

A marine biologist descends in a submarine through the waters of the Black Sea. The top hundred meters or so are well oxygenated, but deeper waters are rich in hydrogen sulfide. What biological metabolisms can explain the distribution of H2S in the Black Sea?

During oxygenic photosynthesis, water is _____ and loses electrons. (i.e., it serves as an electron donor) .

Fermentation yields an amount of energy equivalent to respiration because both processes achieve full oxidation of carbon compounds to CO2.

A researcher is comparing the sequences of genes encoding cell wall proteins in archaeons with those coding cell wall proteins in bacteria. How similar do you expect these sequences will be?

The text discusses the metabolisms that link the N and S cycles to Earth's biological carbon cycle. Can you outline ways in which the carbon cycle might also be linked to the biological cycling of iron?

If biologists could quantify all the bacterial and human cells within the human body, they would find that there are far more human cells.

Autotrophs produce carbohydrates by reducing CO2, whereas heterotrophs synthesize carbohydrates by ingesting smaller preformed organic compounds like glucose.

A doctor is treating a patient for an apparent bacterial infection. She prescribes antibiotics that target either the peptidoglycan in bacterial cell walls or the bacterial translational machinery. To her surprise, this treatment does not work. Why might this treatment be ineffective?

All bacteria are unicellular.

Imagine you are talking to your friend who is very excited because he has just transduced his first batch of bacteria in the laboratory. What does this mean?

Imagine that a scientist is able to reverse the principles of diffusion, such that molecules preferentially move from regions of low concentrations to regions of high concentrations. How would this affect the morphology of bacteria?

Bacteria contain neither organelle-associated membranes nor a cell membrane.

Photoheterotrophs rely on sunlight and organic molecules obtained from the environment.

An organism that oxidizes H2S to gain energy and utilizes CO2 as a carbon source (to generate carbohydrates) would be classified as a:

An organism that acquires energy from the sun and uses C₆H₁₂O₆ as a carbon source would be classified as a:

A marine biologist descends in a submarine through the waters of the Black Sea. The top hundred meters or so are well oxygenated, but deeper waters are rich in hydrogen sulfide. What biological metabolisms can explain the distribution of H₂S in the Black Sea?

Fermentation yields an amount of energy equivalent to respiration because both processes achieve full oxidation of carbon compounds to CO₂.

Autotrophs produce carbohydrates by reducing CO₂, whereas heterotrophs synthesize carbohydrates by ingesting smaller preformed organic compounds like glucose.

An organism that oxidizes H₂S to gain energy and utilizes CO₂ as a carbon source (to generate carbohydrates) would be classified as a: