Metabolism of Proteins and Amino Acids Flashcards
Identify the metabolite that does NOT serve as a precursor of a dietarily essential amino acid:
a. a-Ketoglutarate
b. 3-Phosphoglycerate
c. Glutamate
d. Aspartate
e. Histamine
e. Histamine
Select the one of the following statements that is NOT CORRECT
a. Slenocysteine is present at the active sites of certain human enzymes
b. Selenocysteine is inserted into proteins by a posttranslational process
c. Transamination of dietary a-keto acids can replace the dietary essential amino acids leucine, isoleucine, and valine
d. Conversion ofpeptidyl proline to peptidyl-4-hydroxyproline is accompanied by the incorporation of oxygen into succinate
e. Serine and glycine are interconverted in a single reaction in which terahydrofolate derivatives participate
b. Selenocysteine is inserted into proteins by a posttranslational process
Select the CORRECT answer: The first reaction in the degradation of most of the protein amino acids involves the participation of: a. NAD+ b. Thiamine pyrophosphate (TPP) c. Pyridoxal phosphate d. FAD e. NAD+ and TPP
c. Pyridoxal phosphate
Identify the amino acid that is the major contributor to the transport of nitrogen destine for excretion as urea:
a. Alanine
b. Glutamine
c. Glycine
d. Lysine
e. Ornithine
b. Glutamine
Select the one of the following statements that is NOT CORRECT:
a. Angelman syndrome is associated with a defective ubiquitin E3 ligase
b. Following a protein-rich meal, the splanchnic tissues release predominantly branched-chain amino acids which are taken up by peripheral muscle tissue
c. the rate of hepatic gluconeogenesis form glutamine exceeds that of any other amino acid
d. the L-a-amino oxidase-catalyzed conversion of an a-amino acid to its corresponding a-keto acid is accompanied by the release of NH4+
e. Similar or even identical signs and symptoms can be associated with different mutations of the gene that encodes a given enzyme
c. the rate of hepatic gluconeogenesis form glutamine exceeds that of any other amino acid
d. the L-a-amino oxidase-catalyzed conversion of an a-amino acid to its corresponding a-keto acid is accompanied by the release of NH4+
Select the one of the following statements that is NOT CORRECT:
a. PEST sequences target some proteins for rapid degradation
b. ATP and ubiquitin typically participate in the degradation of membrane-associated proteins and other proteins with long half-lives
c. Ubiquitin molecules are attache to target proteins via non-a peptide bonds
d. The discoverers of ubiquitin-mediated proteins degradation received a Nobel Prize
e. Degradation of ubiquitin-tagged proteins takes place in the proteasome, a multi-subunit macromolecule present in all eukaryotes
b. ATP and ubiquitin typically participate in the degradation of membrane-associated proteins and other proteins with long half-lives
For metabolic disorders of the urea cucle, which statement is NOT CORRECT:
a. Ammonia intoxication is most severe when the metabolic block in the urea cucle occurs prior to the reaction catalyzed by argininosuccinate synthase
b. Clinical symptoms include mental reardation and the avoidance of protein-rich foods
c. Clinical signs can include acidosis
D. Aspartate provides the second nitrogen of argininosuccinate
E. Dietary management focuses on a low-protein diet ingested a s frequent small meals
c. Clinical signs can include acidosis
Select the one of the following statements that is NOT CORRECT:
a. One metabolic function of glutamine is to sequester nitrogen in a nontoxic form
B. Liver glutamate dehydorgenase is allosterically inhibited by ATP and activated by ADP
c. Urea is formed both from absorbed ammonia produced by enteric bacteria and from ammonia generated by tissue metabolic activity
d. The concerted action of glutamate dehydrogenase and glutamate aminotransferase may be termed transdeamination
e. Fumarate generated during biosynthesis of argininosuccinate ultimately forms oxaloacetate in reactions in mitochondria catalyzed successively by fumarase and malate dehydrogenase
e. Fumarate generated during biosynthesis of argininosuccinate ultimately forms oxaloacetate in reactions in mitochondria catalyzed successively by fumarase and malate dehydrogenase
Select the one of the following statements that is NOT CORRECT:
a. Threonine provides the thioethanol moiety for biosynthesis of coenzyme A
b. Histamine arises by decarboxylation of histidine
C. Ornithine serves as a precursor of both spermine and spermidine
D. Serotonin and melatonin are metabolites of tryptophan
E. Glycine, arginin, and methionin each contribute atoms for biosynthesis of creatine
a. Threonine provides the thioethanol moiety for biosynthesis of coenzyme A
Select the one of the following statements that is NOT CORRECT:
a. Excreted creatinine is a function of muscle mass, and can be used to determine whether a patient has provided a complete 24-hour urine specimen
b. many drugs and drug catabolites are excreted in urine as glycine conjugates
c. The major nonprotein metabolic fate of methionine is conversion to S-adenosylmethionine
d. the concentration of histamine in braine hypothalamus exhibits a circadian rhythm
e. Decarboxylation of glutamine forms the inhibitory neurotransmitter GABA (y-aminobutyrate)
e. Decarboxylation of glutamine forms the inhibitory neurotransmitter GABA (y-aminobutyrate)
Which of the following is NOT a hemoprotein? a. Myoglobin b. Cytochrome c C. Catalase D. Cytochrome P450 E. Albumin
E. Albumin
A 30 year old man presented at clinic with a history of intermittent abdominal pain and episodes of confusion and psychiatric problems. laboratory tests revealed increases of urinary aminolevulinate and porphobilinogen. Mutational analysis revealed a mutation in the gene for uroporphyrinogen I synthase (porphobilinogen deaminase). The probable diagnosis was: a. Acute intermittent porphyria b. X-linked sideroblastic anemia C. Congenital erythropoietic porhyria d. porphyria cutanea tarda e. Variegate porphyria
a. Acute intermittent porphyria
Select the one of the following statements that is NOT CORRECT:
a. Bilirubin is a cyclic tetrapyrrole
B. Albumin-bound bilirubin is trasported to the liver
c. High levels of bilirubin can cause damage to the brains of newborn infants
c. Bilirubin contains methyl and vinyl groups
e. Bilirubin does not contain iron
a. Bilirubin is a cyclic tetrapyrrole
