Question 1

Which amino acids are coded for by a single codon?

Accepted Answer

A)  methionine only 
B)  isoleucine only 
C)  methionine and isoleucine 
D)  methionine and tryptophan 
E)  methionine, isoleucine, and tryptophan 
A)  methionine only 
B)  isoleucine only 
C)  methionine and isoleucine 
D)  methionine and tryptophan 
E)  methionine, isoleucine, and tryptophan

Question 2

Briefly describe, in one or two sentences, what the "N-end rule" is.

Accepted Answer

The "N-end rule" is a cellular rule that

Question 3

The ribosome does not have a comparable protease proofreading function like the exonuclease activity found in DNA polymerase. What is the "technical difficulty" that perhaps prevented the easy evolution of such an activity?

Accepted Answer

The ribosome is a complex molecular mach

Question 4

Consider the following hypothetical short mRNA; what would be the sequence of the protein produced if this were translated in an E. coli cell?
5'-AUAGGAGGUUUGACCUAUGCCUCGUUUAUAGCC-3'

Accepted Answer

To determine the sequence of the protein

Question 5

Val-tRNA synthetase will sometimes use threonine as a substrate to charge the tRNA but then rapidly remove the threonine. Propose a mechanism for this proofreading.

Accepted Answer

Valyl-tRNA synthetase (ValRS) is an enzy

Question 6

What would be the consequence to the rate of polypeptide synthesis in bacteria if transcription of mRNA was in the 3´$\rightarrow$ 5´ direction? What would happen if this occurred in eukaryotes?

Accepted Answer

In both bacteria and eukaryotes, the pro

Question 7

A new antibiotic was recently discovered that inhibits prokaryotic protein synthesis. In the presence of the antibiotic, protein synthesis can be initiated, but only dipeptides that remain bound to the ribosome are formed. What specific step of protein synthesis is likely to be blocked by this antibiotic?

Accepted Answer

The specific step of protein synthesis t

Question 8

Which statement is NOT true about RNA editing?

Accepted Answer

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. 
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.

Question 9

Which statement about the elongation phase of protein synthesis is TRUE?

Accepted Answer

A)  At least five high-energy phosphoryl groups are expended for each peptide bond formed. 
B)  During elongation, incoming aminoacylated tRNAs are first bound in the P site. 
C)  Elongation factor EF-Tu facilitates translocation. 
D)  Peptidyl transferase catalyzes the attack of the carboxyl group of the incoming amino acid on an ester linkage in the nascent polypeptide. 
E)  Peptidyl transferase is a ribozyme. 
A)  At least five high-energy phosphoryl groups are expended for each peptide bond formed. 
B)  During elongation, incoming aminoacylated tRNAs are first bound in the P site. 
C)  Elongation factor EF-Tu facilitates translocation. 
D)  Peptidyl transferase catalyzes the attack of the carboxyl group of the incoming amino acid on an ester linkage in the nascent polypeptide. 
E)  Peptidyl transferase is a ribozyme.

Question 10

Posttranslational glycosylation of proteins is inhibited specifically by:

Accepted Answer

A)  chloramphenicol. 
B)  cycloheximide. 
C)  puromycin. 
D)  streptomycin. 
E)  tunicamycin. 
A)  chloramphenicol. 
B)  cycloheximide. 
C)  puromycin. 
D)  streptomycin. 
E)  tunicamycin.

Question 11

Approximately how many NTPs must be converted to NDPs to incorporate one amino acid into a protein?

Accepted Answer

A)  zero 
B)  one 
C)  two 
D)  four 
E)  eight 
A)  zero 
B)  one 
C)  two 
D)  four 
E)  eight

Question 12

Which antibiotic does NOT function by interfering with the translational process?

Accepted Answer

A)  chloramphenicol 
B)  cycloheximide 
C)  penicillin 
D)  puromycin 
E)  streptomycin 
A)  chloramphenicol 
B)  cycloheximide 
C)  penicillin 
D)  puromycin 
E)  streptomycin

Question 13

Which statement is FALSE concerning translation of the apoB gene?

Accepted Answer

A)  apoB is a single gene that is expressed in both liver and intestine. 
B)  The liver produces a longer protein product than the intestine. 
C)  In the intestine, cytidine deaminase converts C nucleotide into a U. 
D)  Guide RNA molecules mostly complementary to RNA to be edited serve as a template. 
E)  Edited mRNA for apoB creates a termination codon from one for glutamine. 
A)  apoB is a single gene that is expressed in both liver and intestine. 
B)  The liver produces a longer protein product than the intestine. 
C)  In the intestine, cytidine deaminase converts C nucleotide into a U. 
D)  Guide RNA molecules mostly complementary to RNA to be edited serve as a template. 
E)  Edited mRNA for apoB creates a termination codon from one for glutamine.

Question 14

Inosine is unable to form a wobble-pair with which nucleotides?

Accepted Answer

A)  A only 
B)  C only 
C)  G only 
D)  U only 
E)  either A or G 
A)  A only 
B)  C only 
C)  G only 
D)  U only 
E)  either A or G

Question 15

The sequence below is found within the protein-coding region of an mRNA. Which effect would you NOT expect to observe if the highlighted C residue were deaminated? …GCUCCGAUGCC…

Accepted Answer

A)  no change to the protein coding sequence 
B)  the formation of a truncated protein 
C)  a serine to leucine substitution 
D)  None of these effects would be observed. 
E)  None of these effects is a potential consequence. 
A)  no change to the protein coding sequence 
B)  the formation of a truncated protein 
C)  a serine to leucine substitution 
D)  None of these effects would be observed. 
E)  None of these effects is a potential consequence.

Question 16

Describe two ways in which synthetic polynucleotides were used in solving the genetic code (you need not describe how the synthetic polynucleotides were made).

Accepted Answer

Synthetic polynucleotides were used in s

Question 17

Number the following steps in the proper order with regard to protein synthesis.
___ Aminoacyl-tRNA binds to the A site.
___ Deacylated tRNA is released from ribosome.
___ Peptide bond formation shifts the growing peptide from the P to the A site.
___ The 50S subunit binds to the initiation complex of the 30S subunit and mRNA.

Accepted Answer

To number the steps in the proper order

Question 18

Indicate whether the following statements are true (T) or false (F).
___ A ribosome is the complex within which protein synthesis occurs.
___ Ribosomes contain many separate proteins.
___ Ribosomes contain many different RNAs.
___ The three ribosomal RNAs in a bacterial ribosome are distributed in three separate, large ribosomal subunits.
___ The catalytic machinery of the ribosome is protein-based.
___ There are four binding sites for aminoacyl-tRNAs on a ribosome.

Accepted Answer

Here are the answers to the statements p

Question 19

Which statement about tRNA molecules is FALSE?

Accepted Answer

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. 
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.

Question 20

The following sequence of four amino acids occurred in the structure of a polypeptide found in a wild-type organism: Leu-Ser-Ile-Arg. Several mutants were isolated, each of which carried a single base pair change in the region of DNA that coded for this amino acid sequence. Their corresponding amino acid sequences are:
Mutant
1
MET-Ser-Ile-Arg
2
Leu-TRP-Ile-Arg
3
Leu-Ser-ARG-Arg
4
Leu-Ser-Ile-PRO
5
Leu-Ser-Ile-TRP
What was the nucleotide sequence of the region of mRNA that coded for the amino acid sequence in the wild-type organism? (Refer to Fig. 27-7)

Accepted Answer

To determine the nucleotide sequence of

Exam 27: Protein Metabolism

Which amino acids are coded for by a single codon?

Briefly describe, in one or two sentences, what the "N-end rule" is.

The ribosome does not have a comparable protease proofreading function like the exonuclease activity found in DNA polymerase. What is the "technical difficulty" that perhaps prevented the easy evolution of such an activity?

Consider the following hypothetical short mRNA; what would be the sequence of the protein produced if this were translated in an E. coli cell? 5'-AUAGGAGGUUUGACCUAUGCCUCGUUUAUAGCC-3'

Val-tRNA synthetase will sometimes use threonine as a substrate to charge the tRNA but then rapidly remove the threonine. Propose a mechanism for this proofreading.

What would be the consequence to the rate of polypeptide synthesis in bacteria if transcription of mRNA was in the 3´ →\rightarrow→ 5´ direction? What would happen if this occurred in eukaryotes?

Which statement is NOT true about RNA editing?

Which statement about the elongation phase of protein synthesis is TRUE?

Posttranslational glycosylation of proteins is inhibited specifically by:

Approximately how many NTPs must be converted to NDPs to incorporate one amino acid into a protein?

Which antibiotic does NOT function by interfering with the translational process?

Which statement is FALSE concerning translation of the apoB gene?

Inosine is unable to form a wobble-pair with which nucleotides?

The sequence below is found within the protein-coding region of an mRNA. Which effect would you NOT expect to observe if the highlighted C residue were deaminated? …GCUCCGAUGCC…

Describe two ways in which synthetic polynucleotides were used in solving the genetic code (you need not describe how the synthetic polynucleotides were made).

Which statement about tRNA molecules is FALSE?

The Foundations of Biochemistry

Water

Amino Acids, Peptides, and Proteins

The Three-Dimensional Structure of Proteins

Protein Function

Enzymes

Carbohydrates and Glycobiology

Nucleotides and Nucleic Acids

DNA-Based Information Technologies

Lipids

Biological Membranes and Transport

Biosignaling

Bioenergetics and Biochemical Reaction Types

Glycolysis, Gluconeogenesis, and the Pentose Phosphate Pathway

Principles of Metabolic Regulation

The Citric Acid Cycle

Fatty Acid Catabolism

Amino Acid Oxidation and the Production of Urea

Oxidative Phosphorylation and Photophosphorylation

Carbohydrate Biosynthesis in Plants and Bacteria

Lipid Biosynthesis

Biosynthesis of Amino Acids, Nucleotides, and Related Molecules

Hormonal Regulation and Integration of Mammalian Metabolism

Genes and Chromosomes

DNA Metabolism

RNA Metabolism

Regulation of Gene Expression

Filters

What would be the consequence to the rate of polypeptide synthesis in bacteria if transcription of mRNA was in the 3´ $\rightarrow$ 5´ direction? What would happen if this occurred in eukaryotes?