Deck 19: Protein Synthesis

Question 1

The Shine-Dalgarno sequence is a

A) Prokaryotic mRNA sequence that binds IF-3
B) Prokaryotic mRNA sequence that binds 16S rRNA of the small ribosomal subunit
C) Prokaryotic mRNA sequence that binds the 16S RNA of the large ribosomal subunit
D) Eukaryotic rRNA sequence that binds the AUG codon of mRNA
E) None of the above are correct

Answer 1

B

Question 2

The initiation phase of prokaryotic translation ends as the GTP molecule bound to ________ is hydrolyzed to GDP and P_i

A) IF-1
B) IF-2
C) IF-3
D) IF-4
E) None of the above is correct

Answer 2

B

Question 3

During the elongation phase of prokaryotic translation the aminoacyl-tRNA must first bind _________ before it can be positioned in the A site.

A) EF-Ts
B) EF-Tu
C) EF-Ts-GDP
D) EF-Ts-GTP
E) EF-Tu-GTP

Answer 3

E

Question 4

________ is an enzymatic activity that hydrolyses the bond linking the completed polypeptide chain and the P site tRNA

A) RF-1
B) EF-G
C) Peptidyl transferase
D) Ribosomal esterase
E) Signal peptidase

Question 5

Prominent prokaryotic posttranslational modifications include all of the following except __________.

A) Glycosylation
B) Methylation
C) Proteolytic processing
D) Prenylation
E) Phosphorylation

Question 6

In prokaryotes most of the control of protein synthesis occurs at the level of ______.

A) Translation
B) Transcription
C) Replication
D) Reverse transcription
E) Posttranslational modification

Question 7

The enzymatic activities coded by the lac operon include all of the following except:

A) Thiogalactoside transacylase
B) Lactose transferase
Χ) -Galactosidase
D) Galactose permease
E) None of the above is correct

Question 8

Translocation in eukaryotes requires _____, which is a GTP binding protein.

A) eEF-1
B) eEF-2
C) eEF-3
D) eEF-4
E) None of the above is correct

Question 9

In eukaryotic translation the 40S complex binds the 60S subunit to form the _______ initiation complex.

A) 80S
B) 88S
C) 90S
D) 100S
E) 108S

Question 10

________ provides the energy needed to move the ribosome along an mRNA.

A) ATP
B) GTP
C) UTP
D) TTP
E) All of the above are correct

Question 11

Polypeptides containing signal peptides are called ________.

A) Zymogens
B) Preproproteins
C) Proproteins
D) All of the above are correct
E) None of the above is correct

Question 12

Phosphorylated dolichol, a polyisoprenoid found in ER membrane, is involved in

A) Polypeptide synthesis
B) Proteolytic cleavage reactions
C) Lipophilic modification reactions
D) Hydroxylation reactions
E) Glycosylation reactions

Question 13

All of the following are involved in signal peptide processing except

A) Ribosomal polypeptide translocation factor
B) SRP receptor protein
C) Docking protein
D) Translocon
E) Stop transfer signal

Question 14

The phrase "global control" refers to:

A) Large alterations in mRNA translation patterns
B) Large alterations in mRNA synthesis patterns
C) Specific changes in rRNA synthesis
D) Specific changes in mRNA synthesis
E) Changes in transcript localization patterns

Question 15

Translational frame shifting

A) Results in the synthesis of more than one polypeptide from a single mRNA
B) Has been observed in cells infected by retroviruses
C) Is the result of a +1 or -1 change in the reading frame of an mRNA
D) Both A and C are correct
E) All of the above are correct

Question 16

All of the following statements concerning eukaryotic mRNA are true except

A) Only a small portion of mRNA enters the cytoplasm
B) Most hnRNA is processed into mRNA
C) Export of mRNA through nuclear pores is carefully controlled
D) mRNA export usually requires a 5'-cap and a 3'-poly A tail
E) None of the above is correct

Question 17

Eukaryotic mRNA stability involves:

A) Reversible adenylation
B) The length of poly (A) tails
C) The binding of specific proteins to certain mRNA sequences
D) The action of various nucleases
E) All of the above are correct

Question 18

_______ are a group of molecules that mediate protein folding.

A) Hsp 70s
B) Chaperonins
C) Docking protein
D) Both A and B are correct
E) All of the above are correct

Question 19

The mRNA that codes for ________ possesses an iron response element.

A) Collagen
B) Elastin
C) Globin
D) Ferritin
E) Thiogalactoside transacetylase

Question 20

Chloramphenicol is an antibiotic that:

A) Inhibits prokaryotic peptidyl transferase
B) Causes mRNA misreading via binding to the 30S subunit
C) Interferes with aminoacyl-tRNA binding via binding to 30S subunit
D) Inhibits eukaryotic peptidyl transferase
E) Inhibits prokaryotic peptide chain elongation

Question 21

Cycloheximide is an antibiotic that

A) Inhibits prokaryotic peptidyl transferase
B) Causes mRNA misreading via binding to 30s subunit
C) Interferes with aminoacyl-tRNA binding via binding to the 30S subunit
D) Inhibits eukaryotic peptidyl transferase
E) Inhibits prokaryotic peptide chain elongation

Question 22

Tetracycline is an antibiotic that

A) Inhibits prokaryotic peptidyl transferase
B) Causes mRNA misreading via binding to 30S subunit
C) Interferes with aminoacyl-tRNA binding to the 30S subunit
D) Inhibits eukaryotic peptidyl transferase
E) Inhibits prokaryotic peptide chain elongation

Question 23

Erythromycin is an antibiotic that

A) Inhibits prokaryotic peptidyl transferase
B) Causes mRNA misreading via binding to 30S subunit
C)Interferes with aminoacyl-tRNA binding via binding to the 30S subunit
D) Inhibits eukaryotic peptidyl transferase
E) Inhibits prokaryotic peptide chain elongation

Question 24

Which of the following antibiotics would be most toxic for humans

A) Tetracycline
B) Chloramphenicol
C) Streptomcyin
D) Cycloheximide
E) Erythromycin

Question 25

Ribonucleoprotein particles

A) Contain an mRNA
B) Contain several types of protein
C) Are found only in prokaryotes
D) Both A and B are correct
E) All of the above are correct

Question 26

________ is a translation factor that possesses a unique histidine residue that can be modified to form diphthamide

A) IF-2
B) EF-Tu
C) EF-Ts
D) eEF-1
E) eEF-2

Question 27

Hydroxylation is a posttranslational modification that

A) Requires ascorbic acid
B) Is catalyzed by several mixed function oxidases
C) Is required for the structural integrity of globin
D) Both A and B are correct
E) All of the above are correct

Question 28

In prokaryotes posttranslational methylation reactions are associated with

A) Signal transduction
B) Chemotaxis
C) S-Adenosylmethionine
D) All of the above are correct
E) None of the above is correct

Question 29

The half-lives of prokaryotic mRNA usually varies between

A) 1 and 3 seconds
B) 1 and 3 minutes
C) 1 and 3 hours
D) 3 and 10 hours
E) None of the above is correct

Question 30

Peptidyl transferase is an enzymatic activity that

A) Catalyzes the release of polypeptides from the ribosomes
B) Is found in an rRNA component of ribosomes
C) Catalyzes the nucleophilic attack of the A site -amino group on the carbonyl carbon of the P side amino acid
D) Catalyses peptide bond formation
E) All of the above are correct

Question 31

Unlike the protein synthesis mechanism in the cytoplasm of eukaryotic cells, mitochondria have _______ stop codes.

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

Question 32

An analysis of the wobble hypothesis suggests that a minimum of _______ RNA's are required to translate all 61 codons plus one for a start codon.

A) 22
B) 32
C) 16
D) 62
E) 30

Question 33

Translation begins with

A) Elongation
B) Initiation
C) Termination
D) Targeting
E) tRNA synthesis

Question 34

Which of the following is a type of posttranslational modification?

A) Removal of signal peptides
B) Carboxylation
C) Methylation
D) Phosphorylation
E) All of the above

Question 35

Protein synthesis requires _____ high energy phosphate bonds per peptide bond.

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

Question 36

An amino acid coded for by a stop signal is

A) Pyrrolysine
B) Lysine
C) Cysteine
D) Selenocysteine
E) Both A and D are correct

Question 37

In eukaryotes which of the following amino acids is often hydroxylated after protein synthesis?

A) Proline
B) Tyrosine
C) Arginine
D) Methionine
E) All of the above

Question 38

Which of the following amino acids is sometimes carboxylated after protein synthesis in eukaryotes

A) Glutamate
B) Aspartate
C) Phenylalanine
D) Lysine
E) Arginine

Question 39

Prokaryotes exclusively use which of the following translational control mechanisms?

A) Negative translational control of ribosomal proteins
B) Global controls
C) RNA specific controls
D) Allosteric modifications of ribosomes
E) Energy depletion

Question 40

Which of the following is a synonymous codon with UCU?

A) AAU
B) UCA
C) GAU
D) AAA
E) CUG

Question 41

Protein synthesis in bacteria involves six functional centers. Which of the following is not one of those centers?

A) Decoding center
B) Aminase transfer center
C) Pepidyl transfer center
D) GTPase associated region
E) A site

Question 42

The peptide emerging from the exit tunnel first encounters a molecular factor called

A) Trigger factor
B) Signal factor
C) Linkage chaperone
D) P-site
E) Translation factor

Question 43

Eukaryotic initiation begins with the assembly of ________________.

A) Preinitiation complex
B) Cap-binding complex
C) Poly-binding complex
D) 48S Initiation complex
E) Translational initiation complex

Question 44

Which of the following compounds is referred to as the twenty-first amino acid?

A) Selenocysteine
B) Glucolysine
C) Cysteine
D) Dehydroxyalinine
E) D-Lysine

Question 45

During synthesis of secreted proteins, binding of the ribosome to the ER membrane is mediated by

A) The translocon
B) SRP and SRP receptor protein
C) Signal peptidase
D) Co-translational transfer
E) Posttranslational translocation

Question 46

What is a Shine-Dalgarno sequence?

Question 47

List the major translational control mechanisms of eukaryotes.

Question 48

What are the goals of proteomic researchers?

Question 49

List and describe four properties of the genetic code.

Question 50

What are the "wobble rules"? What are the consequences of the wobble rules in protein synthesis?

Question 51

Briefly outline the steps in the elongation cycle.of protein synthesis.

Question 52

Describe the structure and function of the signal recognition particle.

Question 53

Why are tRNA's described as adaptor molecules?

Question 54

Explain the roles of the large and small subunits of ribosomes.

Question 55

List and describe the major classes of eukaryotic posttranslational modifications.

Question 56

Explain the importance of proper targeting of nascent polypeptides.

Question 57

Eukaryotic protein synthesis is considerably slower than synthesis of prokaryotes. Explain.

Question 58

Explain the significance of the following statement: The functioning of the aminoacyl-tRNA synthesis is referred to as the second genetic code.

Question 59

Indicate the phase of protein synthesis during which the polypeptide is actually synthesized.

Question 60

What is the energy source used to move mRNA in a ribosome during protein synthesis.

Question 61

Indicate the phase of protein synthesis during which the ribosome dissociates into subunits.

Question 62

Explain the critically important role of aminoacyl-tRNA synthetases in protein synthesis.

Question 63

Given that the amino acid sequence for a polypeptide, can the base sequence for the mRNA that codes for it be predicted?

Question 64

Compare and contrast the coding reassignment mechanisms whereby selenocysteine and pyrolysine are linked to their cognate tRNA's. Explain.

Question 65

Despite considerable species differences in the amino acid and nucleotide sequences of ribosomal proteins and RNA, respectively, the three-dimensional structures of ribosomal protein and ribosomal RNA are remarkably similar among species. Suggest reasons for these similarities.

Question 66

Describe how the base pairing between the Shine-Dalgarno sequence and the 30S subunit provide the means by which a start codon is distinguished from a methionine codon. What is the eukaryotic version of this mechanism?

Question 67

Some aminoacyl-tRNA synthetases that link amino acids with similar side chains (e.g. isoleucine and valine) to their cognate RNA's possess proofreading sites. What sets of amino acids whose structural similarities might also require proofreading?

Question 68

What advantages are there for synthesizing an inactive protein that must be subsequently activated by prostranslational modifications?

Question 69

What factors insure accuracy of protein synthesis? How does the level of accuracy usually attained in protein synthesis compare with that of DNA replication or transcription?

Question 70

Can you suggest a reason why ribosomes in all living organisms consist of two subunits and not one supramolecular complex?

Question 71

A prokaryotic species is facing a new environmental stress that can be ameliorated by a catalytic activity that requires the side chain of a unique amino acid derivative called pyrovaline. What molecule and mechanism would be required for the incorporation of this nonstandard amino acid into a protein molecule?

Question 72

There are four serine codons in the genetic code. A peptide sequence is composed of 10 serine residues. Determine how many different mRNA sequences could code for this molecule?

Question 73

Determine the total number of nucleotides that must be hydrolysed in the synthesis of Lys-Ala-Ser-Val.

Question 74

Estimate the minimum number of ATP and GTP molecules required to polymerize 200 amino acids.