Which of the following is not true of the reaction catalyzed by the pyruvate dehydrogenase complex?
a) biotin participates in the decarboxylation.
b) both nad+ and a flavin nucleotide act as electron carriers.
c) the reaction occurs in the mitochondrial matrix.
d) the substrate is held by the lipoyl-lysine "swinging arm."
e) two different cofactors containing —sh groups participate.

step 1: nitrogen fixation- conversion of atmospheric no₂ into forms useful to plants by lightning, bacteria, and cyanobacteria.

step 2: nitrification-process of converting ammonia to nitrite or nitrate.

step 3: assimilation-plant roots absorb new form of nitrogen.

step 4: ammonification-conversion of organic nitrogen to ammonia by bacteria involved in decomposition.

step 5: denitrification-bacteria turns the decomposed matter back into n₂o, which is released into atmosphere; repeat cycle.