Deck 22: Protein Synthesis

Question 1

The genetic code is said to be _____ because several codons may correspond to the same amino acid.

A) deteriorate
B) despicable
C) degenerate
D) decadent
E) depraved

Answer 1

degenerate

Question 2

Which of the following is the only tRNA loop that is exclusively single stranded RNA?

A) acceptor step
B) D loop
C) T C loop
D) anticodon loop
E) none of the above

Answer 2

none of the above

Question 3

Where is the anticodon in the following structure?

A) 1
B) 2
C) 3
D) 4
E) 5

Answer 3

3

Question 4

What are the predominant interactions between the 30S and 50S subunits that allow the formation of the 70S ribosome?

A) 30S protein with 50S rRNA
B) 30S rRNA with 50S protein
C) protein-protein interactions from both subunits
D) rRNA-rRNA interactions from both subunits
E) interactions of 50S rRNA with tRNA D loop and interactions of 30S rRNA with anticodon loop are the only interactions holding the 70S ribosome together

Question 5

Why does the mRNA adopt a sharp bend as it moves through the ribosome?

A) so that the mRNA can enter the 30S subunit and exit the 50S subunit
B) in order to maximize base pairing with the 23S rRNA
C) so the tRNAs in both the A and P site can interact with their appropriate codons
D) to prevent dissociation of the 30S and 50S subunits
E) all of the above

Question 6

Which of the following tRNA binding sites is correctly defined?

A) A site: accepts incoming aminoacyl-tRNA
B) E site: entrance site for initial tRNA binding
C) P site: site occupied by the tRNA that accepts the growing peptide chain
D) T site: site that is briefly occupied while the tRNA is passed from the A site to P site
E) all of the above

Question 7

Which of the following initiation steps results in GTP hydrolysis?

A) binding of mRNA to the 30S subunit
B) binding of the 50S subunit to the 30S subunit
C) binding of the fMet-tRNA to the ribosome
D) binding of IF-2 to the 30S subunit
E) binding of IF-1 to the A site

Question 8

Which of the following is true regarding the interaction of EF-Tu with aminoacyl-tRNAs?

A) the higher the occurrence of an amino acid in a protein, the stronger the interaction
B) EF-Tu binds charged and uncharged tRNAs with the same affinity
C) free aminoacyl-tRNAs can only bind to the ribosome in vitro
D) binding occurs with about equal affinity for all aminoacyl-tRNAs
E) the interaction always involves the anticodon loop

Question 9

The interaction used to insure correct codon-anticodon recognition involves RNA interactions from _____ that specifically check interactions at _____.

A) mRNA and tRNA; first and second codon positions
B) mRNA and tRNA; second and third codon positions
C) mRNA, tRNA and rRNA; first and second codon positions
D) mRNA, tRNA and rRNA; second and third codon positions
E) mRNA, tRNA and rRNA; all three codon positions

Question 10

Besides the proofreading function of EF-Tu, what other mechanism is used to insure the proper tRNA is in the A site?

A) interaction between the D loop and the 50S subunit
B) interaction between the T C loop and the 30S subunit
C) interaction of the aminoacyl group with certain proteins in the A site
D) interaction of the codon with the 50S subunit
E) none of the above

Question 11

Which of the following is responsible for the catalytic activity of peptidyl transferase?

A) protein component of 50S subunit
B) rRNA component of 50S subunit
C) protein component of 30S subunit
D) rRNA component of 30S subunit
E) both protein and rRNA of the 50S subunit

Question 12

What type of catalysis is seen by the nucleotides in the active site of peptidyl transferase?

A) acid-base catalysis
B) nucleophilic catalysis
C) electrophilic catalysis
D) proximity and orientation effects
E) covalent catalysis

Question 13

What recognizes stop codons?

A) a termination tRNA that does not carry an amino acid on its acceptor stem
B) release factors
C) ribosome recycling factors
D) fMet-tRNA
E) nothing recognizes stop codons, that is why translation ceases

Question 14

Signal recognition particle is a _____ whose function is to _____.

A) DNA-protein complex; transport proteins into the eukaryotic nucleus
B) ribonucleoprotein; direct proteins to the membrane or endoplasmic reticulum
C) chaperone; aid in protein folding
D) glycosylase; catalyze posttranslational modification
E) none of the above

Question 15

Chaperonins such as the GroEL/ES system function _____.

A) only when heat shock proteins are activated
B) in a non-aqueous environment
C) only at low pH
D) only when bound to the ER membrane
E) in an ATP-dependent manner

Question 16

Which of the following commonly occurs at asparagine residues of extracellular proteins?

A) hydrolysis of the amide to form Asp
B) phosphorylation
C) glycosylation
D) peptide cleavage
E) none of the above

Question 17

Which of the following occurs during the post-translational processing of insulin?

A) glycosylation
B) phosphorylation
C) acetylation of lysine residues
D) formation of disulfide bonds
E) amidation of the C-terminal amino acid

Question 18

Attachment of _____ to a Lys residue of a protein targets it for transport into the nucleus.

A) ubiquitin
B) SUMO
C) SRP
D) DnaK
E) trigger factor

Question 19

Which of the following bases is not present in RNA?

A)

B)

C)

D)

E)

Question 20

Which diagram correctly depicts a ribosome engaged in translation?

A)

B)

C)

D)