Discuss the ecological importance of the enzyme nitrogenase, the diversity and physiology of the various groups of organisms that contain it, and the strategies these organisms use to optimize conditions for the enzyme
What will be an ideal response?
Answer: The enzyme nitrogenase is the only enzyme that can catalyze the conversion of nitrogen gas into ammonia, thus it is critical to the N cycle in all ecosystems. Bacteria and Archaea from many different phyla contain nifH (the gene that encodes for the nitrogenase enzyme). Some of the microbes form symbiotic associations with plants and fungi, while others are free-living. The ability to fix nitrogen is not restricted to one particular metabolic group of microbes and nitrogenase can be found in aerobic, anaerobic, heterotrophic, autotrophic, and phototrophic microbes. Nitrogenase is inactivated by oxygen. Microbes that live in aerobic environments or produce oxygen themselves use a variety of strategies to keep nitrogenase and oxygen separate. Examples include specialized cells (heterocysts) that are non-photosynthetic and impermeable to oxygen, production of a thick polysaccharide capsule to prevent oxygen diffusion into the cell, and induction of nitrogenase at night or at times when oxygen concentrations are low.
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What will be an ideal response?
Which of these characteristics is not found in both land plants and green algae?
1.cellulose in their cell walls 2.produce spores in sporangia 3.store energy captured during photosynthesis as starch 4.light-absorbing pigments include both chlorophyll a and chlorophyll b
On the outer surface of the plasma membrane there are marker molecules that identify the cell type. Often these molecules are
A. amino acids. B. carbohydrate chains. C. nucleotides. D. ATP. E. inorganic ions.
In mammals, where in the kidney should you expect to find cells with the highest concentration of osmolytes, such as sorbitol?
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