Concept explainers
REFLECT AND APPLY You are in the process of determining the amino acid sequence of a peptide. After trypsin digestion followed by the Edman degradation, you see the following peptide fragments:
What is abnormal concerning these results? What might have been the problem that caused it?
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Biochemistry
- REFLECT AND APPLY A sample of an unknown peptide was divided into two aliquots. One aliquot was treated with trypsin; the other was treated with cyanogen bromide. Given the following sequences (N-terminal to C-terminal) of the resulting fragments, deduce the sequence of the original peptide. Trypsin treatment AsnThrTrpMetIleLysGlyTyrMetGlnPheValLeuGlyMetSerArg Cyanogen bromide treatment GlnPheValLeuGlyMetIleLysGlyTyrMetSerArgAsnThrTrpMetarrow_forwardREFLECT AND APPLY You are studying with a friend who says that the hydrogen-bonded portions of tRNA play no important role in its function. What is your reply?arrow_forwardREFLECT AND APPLY In prokaryotic protein synthesis, N-formylmethionine (fmet) is the first amino acid incorporated, whereas (normal) methionine is incorporated in eukaryotes. The same codon (AUG) serves both. What prevents methionine from being inserted into the beginning and N-formylmethionine in the interior?arrow_forward
- REFLECT AND APPLY Explain why a 50S ribosomal subunit and a 30S ribosomal subunit combine to form a 70S subunit, instead of an 80S subunit.arrow_forwardREFLECT AND APPLY You are in the process of determining the amino acid sequence of a protein and must reconcile contradictory results. In one trial, you determine a sequence with glycine as the N-terminal amino acid and asparagine as the C-terminal amino acid. In another trial, your results indicate phenylalanine as the N-terminal amino acid and alanine as the C-terminal amino acid. How do you reconcile this apparent contradiction?arrow_forwardREFLECT AND APPLY List three molecular changes that take place in the processing of eukaryotic mRNA.arrow_forward
- REFLECT AND APPLY (a) How many activation cycles are needed for a protein with 150 amino acids? (b) How many initiation cycles are needed for a protein with 150 amino acids? (c) How many elongation cycles are needed for a protein with 150 amino acids? (d) How many termination cycles are needed for a protein with 150 amino acids?arrow_forwardREFLECT AND APPLY The amino acid hydroxyproline is found in collagen. There is no codon for hydroxyproline. Explain the occurrence of this amino acid in a common protein.arrow_forwardREFLECT AND APPLY E. coli has two tRNAs for methionine. What is the basis for the distinction between the two?arrow_forward
- REFLECT AND APPLY Would you expect mRNA or rRNA to be degraded more quickly in the cell? Why?arrow_forwardREFLECT AND APPLY Outline a mechanism by which RNA can catalyze its own self-splicing.arrow_forwardREFLECT AND APPLY Common proteins are polymers of 20 different amino acids. How big a protein (how many amino acid residues) would be necessary to have an Avogadros number of possible sequences?arrow_forward
- BiochemistryBiochemistryISBN:9781305961135Author:Mary K. Campbell, Shawn O. Farrell, Owen M. McDougalPublisher:Cengage Learning