Chapter 30

Question 1

During translation, the mRNA is read in the _____ direction and protein synthesized in the _____ direction.

Answer 1

5′-to-3′; amino-to-carboxyl

Question 2

During attachment of an amino acid to its tRNA, how is ATP required?

Answer 2

The ATP forms an amino acyl adenylate that transfers the activated amino acid to the tRNA.

Question 3

The codon AUG specifies either initiation of protein synthesis or an internal methionine. What would be the sequence of the anticodon of a tRNA that binds to this codon?

Answer 3

5-CAU-3

Question 4

During ribosomal protein synthesis, the growing peptide chain

Answer 4

is transferred from the tRNA in the P site to the amino acyl tRNA in the A site.

Question 5

During protein synthesis, which of the following is NOT an energy-requiring step

Answer 5

formation of the peptide bond

Question 6

Termination of protein synthesis occurs when a stop or termination codon is in the A site. This occurs because

Answer 6

these codons are recognized by specific proteins which also release the newly synthesized protein chain from the ribosome.

Question 7

Puromycin is an antibiotic that functions by inhibiting protein synthesis. It does this by

Answer 7

causing premature release of protein chains being synthesized.

Question 8

Where does wobble occur in the tRNA-mRNA recognition?

Answer 8

5´ base of the anticodon

Question 9

Which of the following would be effective at blocking translation of a specific mRNA while allowing other mRNA molecules to undergo translation?

Answer 9

antisense mRNA

Question 10

Which of the following provides the energy for the cotranslational movement of proteins across the endoplasmic reticulum?

Answer 10

peptide bond formation powered by hydrolysis of aminoacyl-tRNAs

Question 11

What sequence allows bacterial ribosomes to identify the correct AUG start codon?

Answer 11

Shine-Dalgarno sequence

Question 12

Which of the following details how SRP allows proteins to be transported into the ER?

Answer 12

SRP binds the peptide signal sequence and inhibits further translation until it interacts with its receptor.

Question 13

Amino acids are attached to tRNA at the _____ end following the _____ sequence of the acceptor stem.

Answer 13

3’; CCA

Question 14

If the anticodon of a tRNA molecule is 3’-AGU-5’, what is the matching codon?

Answer 14

UCA

Question 15

Fidelity of protein synthesis is increased because:

Answer 15

They do not form double-helical regions.

Question 16

Which of the following is NOT found in a eukaryotic ribosome?

Answer 16

DNA duplexes

Question 17

Which of the following is a common characteristic of a protein enzyme and catalytic RNA

Answer 17

catalytic groups oriented in a specific manner within the molecule
defined secondary structure
defined tertiary structure
specific interactions between the monomers that comprise the macromolecule

Question 18

When a bacterial ribosome has formed the final “initiation complex,” which of the following has occurred?

Answer 18

The 30S and 50S subunits have combined to form the 70S ribosome.

Question 19

The mRNA from a prokaryote contains this purine-rich region that precedes the initiating codon and base-pairs with complementary nucleotides in the ribosomal RNA.

Answer 19

the Shine–Dalgarno sequence

Question 20

What is a polyribosome?

Answer 20

a group of ribosomes bound to a single mRNA

Question 21

How does the drug puromycin work to inhibit protein synthesis?

Answer 21

It resembles an aminoacyl-tRNA, enters the A site and becomes covalently attached to the growing peptide, thus terminating translation.

Question 22

Which of the following antibiotics acts by inhibiting peptidyl transferase activity of the 50S ribosomal subunit

Answer 22

chloramphenicol

Question 23

Which of the following is TRUE of puromycin

Answer 23

Proteins synthesized in the presence of puromycin would be covalently modified on their C-termini.

Question 24

The antibiotic _____ inhibits prokaryotic ribosomes but not eukaryotic ribosomes by exploiting the fact that _____

Answer 24

streptomycin; prokaryotic initiation depends on formylmethionyl-tRNA binding

Question 25

Which of the following binds the A site of the ribosome as part of its action?

Answer 25

puromycin

Question 26

Diphtheria toxin blocks protein synthesis by

Answer 26

inhibiting translocation.

Question 27

Proteins destined for excretion from the cell are ultimately synthesized on ribosomes located

Answer 27

on the rough endoplasmic reticulum

Question 28

Signal sequences on nascent proteins are recognized and bound by the _____ in the cytoplasm, which directs the translating ribosome to the ER.

Answer 28

signal recognition particle

Question 29

During the synthesis of a secretory protein, the _____ subunit of the ribosome interacts with the _____.

Answer 29

60S; translocon

Question 30

mRNA encoding a lysosomal protease will contain codons for a stretch of _____ amino acids located _____ of the start codon.

Answer 30

hydrophobic; 3’