Module 24 - Chp 27 Protein Metabolism
1. A certain bacterial mRNA is known to represent only one gene and to contain about 800
nucleotides. If you assume that the average amino acid residue contributes 110 to the
peptide molecular weight, the largest polypeptide that this mRNA could code for would have
a molecular weight of about:
A) 800.
B) 5,000.
C) 30,000.
D) 80,000.
E) An upper limit cannot be determined from the data given. - ANS-C) 30,000
\2. Assuming that the average amino acid residue contributes 110 to the peptide molecular
weight, what will be the minimum length of the mRNA encoding a protein of molecular weight
50,000?
A) 133 nucleotides
B) 460 nucleotides
C) 1,400 nucleotides
D) 5,000 nucleotides
E) A minimum length cannot be determined from the data given. - ANS-C) 1,400 nucleotides
\3. Which statement describes a feature of the wobble hypothesis?
A) A naturally occurring tRNA exists in yeast that can read both arginine and lysine codons.
B) A tRNA can recognize only one codon.
C) Some tRNAs can recognize codons that specify two different amino acids if both are
nonpolar.
D) The "wobble" occurs only in the first base of the anticodon.
E) The "wobble" occurs only in the third base of the anticodon. - ANS-D) The "wobble"
occurs only in the first base of the anticodon.
\4. Which statement is TRUE about the genetic code?
A) All codons recognized by a given tRNA encode different amino acids.
B) It is absolutely identical in all living things.
C) Several different codons may encode the same amino acid.
D) The base in the middle position of the tRNA anticodon sometimes permits "wobble" base
pairing with two or three different codons.
E) The first position of the tRNA anticodon is always adenosine. - ANS-C) Several different
codons may encode the same amino acid.
\5. Which statement is NOT true about RNA editing?
A) RNA editing occurs mostly in mitochondria and chloroplasts.
B) RNA editing requires guide RNAs that have sequences complementary to the edited
mRNA.
C) Deamination of G is a common reaction in RNA editing.
, D) Deamination of A is common reaction in RNA editing.
E) RNA editing allows for the synthesis of two different proteins from one gene. - ANS-C)
Deamination of G is a common reaction in RNA editing.
\6. Which step is NOT one of the five steps of protein synthesis?
A) termination and ribosome degradation
B) elongation of the peptide chain
C) initiation of peptide synthesis
D) activation of the amino acids
E) protein folding and posttranslational processing - ANS-A) termination and ribosome
degradation
\7. Which statement about ribosomes is TRUE?
A) The large subunit contains rRNA molecules; the small subunit does not.
B) The RNA in ribosomes plays a structural, not catalytic, role.
C) There are about 25 ribosomes in an E. coli cell.
D) There are two major ribosomal subunits, each with multiple proteins.
E) Ribosomes are relatively small, with molecular weights less than 10,000. - ANS-D) There
are two major ribosomal subunits, each with multiple proteins.
\8. Which statement about tRNA molecules is FALSE?
A) A, C, G, and U are the only bases present in the molecule.
B) Although composed of a single strand of RNA, each molecule contains several short,
double-helical regions.
C) Any given tRNA will accept only one specific amino acid.
D) The amino acid attachment is always to an A nucleotide at the 3' end of the molecule.
E) There is at least one tRNA for each of the 20 amino acids. - ANS-A) A, C, G, and U are
the only bases present in the molecule.
\9. Which statement about the tRNA that normally accepts phenylalanine is FALSE? (mRNA
codons for phenylalanine are UUU and UUC.)
A) It interacts specifically with the Phe synthetase.
B) It will accept only the amino acid phenylalanine.
C) Its molecular weight is about 25,000.
D) Phenylalanine can be specifically attached to an —OH group at the 3' end.
E) The tRNA must contain the sequence UUU. - ANS-E) The tRNA must contain the
sequence UUU.
\10. Which statement is NOT true of tRNA molecules?
A) The 3'-terminal sequence is —CCA.
B) Their anticodons are complementary to the triplet codon in the mRNA.
C) They contain more than four different bases.
D) They contain several short regions of double helix.
E) With the right enzyme, any given tRNA molecule will accept any of the 20 amino acids. -
ANS-E) With the right enzyme, any given tRNA molecule will accept any of the 20 amino
acids.
\11. Aminoacyl-tRNA synthetases (amino acid activating enzymes):
1. A certain bacterial mRNA is known to represent only one gene and to contain about 800
nucleotides. If you assume that the average amino acid residue contributes 110 to the
peptide molecular weight, the largest polypeptide that this mRNA could code for would have
a molecular weight of about:
A) 800.
B) 5,000.
C) 30,000.
D) 80,000.
E) An upper limit cannot be determined from the data given. - ANS-C) 30,000
\2. Assuming that the average amino acid residue contributes 110 to the peptide molecular
weight, what will be the minimum length of the mRNA encoding a protein of molecular weight
50,000?
A) 133 nucleotides
B) 460 nucleotides
C) 1,400 nucleotides
D) 5,000 nucleotides
E) A minimum length cannot be determined from the data given. - ANS-C) 1,400 nucleotides
\3. Which statement describes a feature of the wobble hypothesis?
A) A naturally occurring tRNA exists in yeast that can read both arginine and lysine codons.
B) A tRNA can recognize only one codon.
C) Some tRNAs can recognize codons that specify two different amino acids if both are
nonpolar.
D) The "wobble" occurs only in the first base of the anticodon.
E) The "wobble" occurs only in the third base of the anticodon. - ANS-D) The "wobble"
occurs only in the first base of the anticodon.
\4. Which statement is TRUE about the genetic code?
A) All codons recognized by a given tRNA encode different amino acids.
B) It is absolutely identical in all living things.
C) Several different codons may encode the same amino acid.
D) The base in the middle position of the tRNA anticodon sometimes permits "wobble" base
pairing with two or three different codons.
E) The first position of the tRNA anticodon is always adenosine. - ANS-C) Several different
codons may encode the same amino acid.
\5. Which statement is NOT true about RNA editing?
A) RNA editing occurs mostly in mitochondria and chloroplasts.
B) RNA editing requires guide RNAs that have sequences complementary to the edited
mRNA.
C) Deamination of G is a common reaction in RNA editing.
, D) Deamination of A is common reaction in RNA editing.
E) RNA editing allows for the synthesis of two different proteins from one gene. - ANS-C)
Deamination of G is a common reaction in RNA editing.
\6. Which step is NOT one of the five steps of protein synthesis?
A) termination and ribosome degradation
B) elongation of the peptide chain
C) initiation of peptide synthesis
D) activation of the amino acids
E) protein folding and posttranslational processing - ANS-A) termination and ribosome
degradation
\7. Which statement about ribosomes is TRUE?
A) The large subunit contains rRNA molecules; the small subunit does not.
B) The RNA in ribosomes plays a structural, not catalytic, role.
C) There are about 25 ribosomes in an E. coli cell.
D) There are two major ribosomal subunits, each with multiple proteins.
E) Ribosomes are relatively small, with molecular weights less than 10,000. - ANS-D) There
are two major ribosomal subunits, each with multiple proteins.
\8. Which statement about tRNA molecules is FALSE?
A) A, C, G, and U are the only bases present in the molecule.
B) Although composed of a single strand of RNA, each molecule contains several short,
double-helical regions.
C) Any given tRNA will accept only one specific amino acid.
D) The amino acid attachment is always to an A nucleotide at the 3' end of the molecule.
E) There is at least one tRNA for each of the 20 amino acids. - ANS-A) A, C, G, and U are
the only bases present in the molecule.
\9. Which statement about the tRNA that normally accepts phenylalanine is FALSE? (mRNA
codons for phenylalanine are UUU and UUC.)
A) It interacts specifically with the Phe synthetase.
B) It will accept only the amino acid phenylalanine.
C) Its molecular weight is about 25,000.
D) Phenylalanine can be specifically attached to an —OH group at the 3' end.
E) The tRNA must contain the sequence UUU. - ANS-E) The tRNA must contain the
sequence UUU.
\10. Which statement is NOT true of tRNA molecules?
A) The 3'-terminal sequence is —CCA.
B) Their anticodons are complementary to the triplet codon in the mRNA.
C) They contain more than four different bases.
D) They contain several short regions of double helix.
E) With the right enzyme, any given tRNA molecule will accept any of the 20 amino acids. -
ANS-E) With the right enzyme, any given tRNA molecule will accept any of the 20 amino
acids.
\11. Aminoacyl-tRNA synthetases (amino acid activating enzymes):
