| A | B |
|---|
| essential amino acids | must be obtained in the diet |
| amino acids | required to build proteins |
| nitrogen | constitutes about 80% of the atmosphere |
| nitrogen fixation | an enzyme is required to catalyze the reduction of nitrogen to ammonia |
| cumulative feedback inhibition | the degree of inhibition increases as more inhibitors bind |
| serine | the major biosynthetic precursor of both glycine and cysteine |
| glutamate | a precursor of arginine |
| ornithine | converted to arginine by reactions of the urea cycle |
| phenylpyruvate | when this increases it causes mental retardation known as phenylketonuria |
| aspartate | a precursor of lysine, methionine, threonine, and isoleucine |
| urea cycle | converts ammonia to urea |
| ammonia | highly toxic for animals and plants |
| ureogenesis | synthesis of urea in the liver |
| four | amount of ATP consumed per molecule of urea synthesized |
| glucogenic | amino acids that are degraded to pyruvate and can supply gluconeogenesis |
| ketogenic | amino acids that contribute to the formation of fatty acids or ketone bodies |
| alanine | what amino acid gives rise to pyruvate, aspartate to oxaloacetate, and glutamate to alpha-ketoglutarate |
| methionine | is converted to the activated methyl donor S-adenosylmethionine |
| tyrosine | both glucogenic and ketogenic |
| nitric oxide synthase | catalyzes the formation of nitric oxide and citrulline from arginine |
