Question 1

A newly discovered microorganism obtains its energy from inorganic chemicals and uses carbon dioxide ($CO_2$) as its sole carbon source. How should this organism be classified?

Accepted Answer

Chemoautotroph

Question 2

Which of the following best describes a photoheterotroph?

Accepted Answer

Uses light as an energy source and organic compounds as a carbon source

Question 3

Most medically important microbes belong to which metabolic group?

Accepted Answer

Chemoheterotrophs

Question 4

A bacterium living deep underground in rocks, with little or no access to organic material or sunlight, is most likely classified as which of the following?

Accepted Answer

Chemoautotroph

Question 5

Which of the following is a possible final electron acceptor for chemoheterotrophs during anaerobic respiration?

Accepted Answer

$NO_3^-$ (nitrate)

Question 6

Which term describes an organism that uses light as its energy source and $CO_2$ as its carbon source?

Accepted Answer

Photoautotroph

Question 7

Which of the following best describes a chemotroph?

Accepted Answer

An organism that obtains energy from chemical compounds

Question 8

A microbe that uses $H_2S$ as an energy source and $CO_2$ as a carbon source is best classified as:

Accepted Answer

Chemoautotroph

Question 9

Which of the following statements about oxygenic and anoxygenic organisms is correct?

Accepted Answer

Oxygenic organisms produce $O_2$ as a byproduct of photosynthesis, while anoxygenic organisms do not.

Question 10

Which of the following is NOT a possible final electron acceptor for chemoheterotrophs?

Accepted Answer

$CO_2$

Question 11

A microbe isolated from a hot spring uses sunlight for energy and organic acids for carbon. Which group does it belong to?

Accepted Answer

Photoheterotroph

Question 12

Which of the following best describes the difference between a chemoautotroph and a chemoheterotroph?

Accepted Answer

Chemoautotrophs use $CO_2$ as a carbon source, while chemoheterotrophs use organic compounds as a carbon source.

Question 13

Which of the following scenarios best illustrates a real-world application of a chemoautotroph?

Accepted Answer

Bacteria oxidizing iron in deep-sea hydrothermal vents to fix $CO_2$ into organic matter

Question 14

Which of the following is the best definition of a phototroph?

Accepted Answer

An organism that uses light as its primary energy source

Question 15

A microbe is found to use $O_2$ as a final electron acceptor and organic compounds as both its energy and carbon source. Which group does it belong to?

Accepted Answer

Chemoheterotroph

Question 16

Which of the following is a common misconception about photoautotrophs?

Accepted Answer

They use organic compounds as their carbon source.

Question 17

Which of the following best describes the energy and carbon sources for a chemoheterotroph?

Accepted Answer

Organic compounds for both energy and carbon

Question 18

A student claims that all phototrophs are oxygenic. Which of the following best refutes this claim?

Accepted Answer

Some phototrophs, such as purple sulfur bacteria, are anoxygenic and do not produce $O_2$.

Question 19

Which of the following is the best example of a final electron acceptor used by chemoheterotrophs in anaerobic conditions?

Accepted Answer

$SO_4^{2-}$ (sulfate)

Question 20

A microbe is isolated from a cave and is found to use light as an energy source and $CO_2$ as a carbon source, but does not produce $O_2$ as a byproduct. Which term best describes this organism?

Accepted Answer

Anoxygenic photoautotroph

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