8.E: Microbial Metabolism (Exercises)
- Page ID
- 78151
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8.1: Biogeochemical Cycles
Energy flows directionally through ecosystems, entering as sunlight for phototrophs or as inorganic molecules for chemoautotrophs. The six most common elements associated with organic molecules—carbon, hydrogen, nitrogen, oxygen, phosphorus, and sulfur—take a variety of chemical forms and may exist for long periods in the atmosphere, on land, in water, or beneath earth’s surface.
Multiple Choice
Which of the following is the group of archaea that can use CO2 as their final electron acceptor during anaerobic respiration, producing CH4?
- methylotrophs
- methanotrophs
- methanogens
- anoxygenic photosynthesizers
- Answer
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C
Which of the following processes is not involved in the conversion of organic nitrogen to nitrogen gas?
- nitrogen fixation
- ammonification
- nitrification
- denitrification
- Answer
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A
Which of the following processes produces hydrogen sulfide?
- anoxygenic photosynthesis
- oxygenic photosynthesis
- anaerobic respiration
- chemoautrophy
- Answer
-
C
The biogeochemical cycle of which of the following elements is based on changes in solubility rather than redox chemistry?
- carbon
- sulfur
- nitrogen
- phosphorus
- Answer
-
D
Fill in the Blank
The molecule central to the carbon cycle that is exchanged within and between ecosystems, being produced by heterotrophs and used by autotrophs, is ________.
- Answer
-
carbon dioxide
The use of microbes to remove pollutants from a contaminated system is called ________.
- Answer
-
bioremediation
True/False
There are many naturally occurring microbes that have the ability to degrade several of the compounds found in oil.
- Answer
-
True
Short Answer
Why must autotrophic organisms also respire or ferment in addition to fixing CO2?
How can human activity lead to eutrophication?
Critical Thinking
In considering the symbiotic relationship between Rhizobium species and their plant hosts, what metabolic activity does each organism perform that benefits the other member of the pair?