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Section VI – Metabolism of Proteins & Amino Acids
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Select the one of the following statements that is NOT CORRECT:
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A. Δ1-Pyrroline-5-carboxylate is an intermediate both in the biosynthesis and in the catabolism of L-proline.
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B. Human tissues can form dietarily nonessential amino acids from amphibolic intermediates or from dietarily essential amino acids.
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C. Human liver tissue can form serine from the glycolytic intermediate 3-phosphoglycerate.
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D. The reaction catalyzed by phenylalanine hydroxylase interconverts phenylalanine and tyrosine.
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E. The reducing power of tetrahydrobiopterin derives ultimately from NADPH.
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Phenylalanine hydroxylase catalyzes a functionally irreversible reaction, and thus cannot convert tyrosine to phenylalanine.
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Identify the metabolite that does NOT serve as a precursor of a dietarily essential amino acid:
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Histamine is a catabolite, not a precursor, of histidine.
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Select the one of the following statements that is NOT CORRECT:
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A. Selenocysteine is present at the active sites of certain human enzymes.
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B. Selenocysteine is inserted into proteins by a posttranslational process.
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C. Transamination of dietary α-keto acids can replace the dietary essential amino acids leucine, isoleucine, and valine.
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D. Conversion of peptidyl proline to peptidyl-4-hydroxyproline is accompanied by the incorporation of oxygen into succinate.
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E. Serine and glycine are interconverted in a single reaction in which tetrahydrofolate derivatives participate.
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The insertion of selenocysteine into a peptide occurs during, not subsequent to translation.
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Select the Correct answer:
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The first reaction in the degradation of most of the protein amino acids involves the participation of:
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B. Thiamine pyrophosphate (TPP)
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Pyridoxal-dependent transamination is the first reaction in degradation of all the common amino acids except threonine, lysine, proline, and hydroxyproline.
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Identify the amino acid that is the ...