Animals are totally dependent on plants and microorganisms for nitrogen fixation and nitrate assimilation because animals: a. do not have the reducing power (nadph) to fix nitrogen. b. lack the enzyme aminotransferase. c. lack the enzymes to reduce n2 and no3- to nh4+. d. lack carbamoyl-phosphate synthetase i. e. lack glutamate dehydrogenase.

C. lack the enzymes to reduce N2 and NO3- to NH4+

Explanation:

Nitrogen fixation is a process by which atmospheric nitrogen (N2) is converted into ammonia (NH3) so that can be used in metabolic pathways (e.g. biosynthesis of macromolecules). Nitrogen fixation is performed by Archea and bacteria such as Azotobacter (usually in symbiosis with Leguminosa plants).

Nitrogen assimilation is a process in which organic compounds are made from inorganic nitrogen.

The only true statement is that cellular respiration is used by every living cell. There are two forms of cellular respiration: aerobic, where oxygen is required, and anaerobic, where it is not.

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