Deck 30: Protein Synthesis

Question 1

What hypothesis explains why some tRNA molecules can bind to more than one codon?

A) jiggle hypothesis
B) shimmy hypothesis
C) teeter hypothesis
D) totter hypothesis
E) wobble hypothesis

Answer 1

E

Question 2

Initiation, elongation, and termination all require factors that are members of the ______________________ family.

Answer 2

G-protein

Question 3

The first amino acid in bacterial proteins is __________________

Answer 3

N-formylmethionine or f-Met

Question 4

The error frequency of protein synthesis is approximately _____________.

Question 5

What biomolecule delivers the aminoacyl-tRNA to the "A site" of the E. coli ribosome?

A) initiation factor-1
B) initiation factor-3
C) elongation factor-G
D) elongation factor-Ts
E) elongation factor-Tu

Question 6

What term describes the RNA-directed process of protein synthesis?

A) transcription
B) translation
C) Merrifield synthesis
D) ribozyme-directed protein synthesis
E) None of the answers is correct.

Question 7

What protein is toxic because it hydrolyzes a critical adenine base from the 28S rRNA molecule in eukaryotes?

A) chloramphenicol
B) ricin
C) puromycin
D) erythromycin
E) tetrodotoxin

Question 8

What sequence identifies a protein for translocation across the ER?

A) signal sequence
B) Shine-Dalgarno sequence
C) poly-A sequence
D) endoplasmic sequence
E) cargo sequence

Question 9

What term refers to the polygenic nature of bacterial mRNA?

A) polytranslated mRNA
B) polytranscribed mRNA
C) polycistronic mRNA
D) polymeric mRNA
E) None of the answers is correct.

Question 10

The signal sequence that marks a protein for translocation across the endoplasmic reticulum membrane is located near the ____________________ end of the protein.

Question 11

Proteins are synthesized in the __________________ direction.

Question 12

What proteins recognize UAA, UAG, and UGA codons?

A) initiation factors
B) elongation factors
C) termination factors
D) release factors
E) 30s ribosome subunit

Question 13

Proteins destined for extracellular release must first bind to the _________________ in the lumen of the ER.

Question 14

What is another name for an amino acid ester of a tRNA?

A) linked tRNA
B) loaded tRNA
C) esterified tRNA
D) charged tRNA
E) filled tRNA

Question 15

Class ____________ aminoacyl-tRNA synthetases acylate the 2′ hydroxyl group of the terminal adenosine of tRNA.

Question 16

Where is the amino acid attached to a tRNA molecule?

A) 3'-hydroxyl of an adenine residue
B) 5'-hydroxyl of a uridine residue
C) 2'-hydroxyl of a guanine residue
D) 3'-hydroxyl of a cytosine residue
E) 2'-hydroxyl of a guanine residue.

Question 17

Aminoacyl-tRNA synthetases contain both an activation site and a(n) __________________ site.

Question 18

In E. coli, the signal sequence that properly aligns the initiation codon in the P site is called the ______________________ sequence.

Question 19

The activation of a tRNA involves the formation of a(n) __________________ intermediate.

Question 20

What region of a tRNA often contains large amounts of inosine?

A) acceptor arm
B) D arm
C) T $\Psi$ C arm
D) anticodon loop
E) extra arm

Question 21

What is the amino acid error rate in protein synthesis? Is this rate logical in evolutionary terms of function?

Question 22

Which of the following is (are) required for initiation of protein synthesis in bacteria?

A) mRNA
B) the 30S subunit
C) fmet-tRNA_f
D) GTP
E) All of the answers are correct.

Question 23

What factor(s) is (are) necessary for the correct placement of the mRNA and initiating tRNA on the ribosome?

A) IF1
B) IF2
C) IF3
D) IF1 and IF2
E) All the answers are correct.

Question 24

Signals that define the beginning and end of protein synthesis are contained in

A) rRNA.
B) tRNA.
C) mRNA.
D) ribosome.
E) protein.

Question 25

The rate of translation in E. coli is ________ amino acids per second.

A) 5
B) 20
C) 50
D) 120
E) None of the answers is correct.

Question 26

Which component of the tRNA is most important for the binding specificity of the tRNA synthetase?

A) variable loop
D) CCA 3ʹ terminus
B) anticodon loop
E) DHU loop
C) TΨC loop

Question 27

What are some of the features common to tRNA molecules?

A) Each is a single chain between 73 and 93 ribonucleotides.
B) They contain many unusual bases.
C) About half the nucleotides in tRNA are base-paired.
D) They usually have a pG at the 5′ terminal.
E) All of the answers are correct.

Question 28

What is the function of the B segment of diphtheria toxin?

A) mimics aminoacyl-tRNA, thus causing premature termination of protein synthesis
B) cleaving tRNA
C) allowing the A fragment to enter the cell
D) covalent modification of elongation factor 2
E) None of the answers is correct.

Question 29

In preparation for attachment to the tRNA, amino acids are activated by

A) methylation.
D) formylation.
B) adenylation.
E) None of the answers is correct.
C) N-acetylation.

Question 30

How much energy is used to attach the amino acid to the tRNA?

Question 31

The ribosome is thought to be

A) an example of a catalyst that has survived from the RNA world.
B) unique to eukaryotes.
C) a ribozyme.
D) a protein catalyst.
E) an example of a catalyst that has survived from the RNA world and a ribozyme.

Question 32

Which of the following E. coli proteins is responsible for translocation of the mRNA as a result of a conformation change due to the hydrolysis of GTP?

A) RRF
D) Shine-Dalgarno
B) EF-Tu
E) None of the answers is correct.
C) EF-G

Question 33

The actual three-dimensional structure of tRNA is

A) overall L-shaped.
D) cylindrical.
B) cloverleaf.
E) None of the answers is correct.
C) twisted triple helix.

Question 34

Explain why some bases in some RNAs cannot be involved in base pairs.

Question 35

Eukaryotic and bacterial translation differ primarily in the ________ step(s).

A) initiation
D) All of the answers are correct.
B) elongation
E) None of the answers is correct.
C) termination

Question 36

What is the direction of translation of mRNA?

A) bidirectional
B) 5' to 3'
C) 3' to 5'
D) 5' to 3' in bacteria, 3' to 5' in eukaryotes
E) 5' to 3' in eukaryotes, 3' to 5' in bacteria

Question 37

Protein synthesis takes place on

A) lysozomes.
D) ribosomes
B) nuclear pores.
E) None of the answers is correct.
C) vacuoles.

Question 38

What is the order of the tRNA binding sites on the 70S ribosome with respect to the 5′-3′ direction of the mRNA?

A) E P A
B) P A E
C) A E P
D) E A P
E) A P E

Question 39

Where is the attachment site and where is the anticodon loop with respect to the nucleotide sequence and with respect to the L-shaped structure of tRNA?

Question 40

What is the function of yeast alanyl-tRNA?

Question 41

How does puromycin inhibit protein synthesis?

Question 42

How do class I and class II aminoacyl tRNA synthetases differ?

Question 43

Describe the subunits of E. coli ribosomes.

Question 44

How does the size of an amino acid influence accurate attachment of the amino acid to the tRNA in aminoacyl-tRNA synthetase reactions?

Question 45

How is a high level of fidelity maintained in attaching the amino acids to the tRNA structure?

Question 46

Using structures of the base pairs, show how the presence of inosine at the 5′ position of the anticodon can recognize three different codons.

Question 47

What are the names for the tRNA binding sites on the ribosome?

Question 48

What role does the amino acid itself play in the accurate placement of the charged tRNA at the codon?