Biochem Test 5

Front 1

Monocistronic

Back 1

Encoding a single polypeptide (Eukaryotic mRNA)

Front 2

Polycistronic

Back 2

Encoding several polypeptides (Prokaryotic mRNA)

Front 3

5' end is capped and has a
100-200 nucleotide long polyadenylate tail

Back 3

Eukaryotic mRNA

Front 4

Usually, the translational initiation signal

Back 4

AUG

Front 5

Usually, the translational stop signals

Back 5

UAA, UAG, UGA

Front 6

A change in a single base pair

Back 6

Point mutation

Front 7

When a mutation occurs in the third position of a degenerate codon

Back 7

Silent mutation

Front 8

Base changes that causes incorporation of a different amino acid in an encoded protein

Back 8

Missense mutation

Front 9

Formation of a termination codon from one that encodes an amino acid

Back 9

Nonsense mutation

Front 10

Mutation of a termination codon to one for an amino acid

Back 10

"Read through" mutation

Front 11

Often caused by insertions or deletions that are not multiples of 3

Back 11

Frameshift mutation

Front 12

A conserved cloverleaf secondary structure

Back 12

tRNA

Front 13

Translation of the codons of ______ involves their direct interaction with complementary anticodon sequences in ________

Back 13

mRNA; tRNA

Front 14

Codon-anticodon base pairing is ________

Back 14

anti-parallel

Front 15

The two-step process of amino acid ________ is catalyzed by a family of ________.

Back 15

activation; aminoacyl-tRNA synthetases

Front 16

Small subunit of cytosolic ribosomes

Back 16

40S

Front 17

Large subunit of cytosolic ribosomes

Back 17

60S

Front 18

Small subunit of mitochondial ribosomes

Back 18

30S

Front 19

Large subunit of mitochondrial ribosomes

Back 19

50S

Front 20

Ribosomes contain two dissimilar subunits, each of which contains ________ and ________

Back 20

RNA; many proteins

Front 21

P site

Back 21

Peptidyl-tRNA binding site

Front 22

A site

Back 22

Acceptor site, or aminoacyl-tRNA binding site

Front 23

E site

Back 23

Exit site for growing peptide chain

Front 24

eIF-4a serves as ________ in translation in eukaryotes

Back 24

RNA helicase

Front 25

PAB

Back 25

PolyA-binding protein

Front 26

Large subunit binding completes formation of the ________

Back 26

Initiation complex

Front 27

When a termination codon (UAG, UAA, or UGA) in mRNA occupies the A site, binding of a release factor (eRF)-GTP complex occurs and ________ is released

Back 27

Deacylated tRNA

Front 28

Peptidyltransferase functions as a ________

Back 28

Hydrolase

Front 29

________ components of the complex can enter additional rounds of protein synthesis

Back 29

Dissociated

Front 30

What is the net cost of amino acid activation?

Back 30

2 high-energy phosphates

Front 31

Some proteins emerge from the ribosome ready to function while others undergo a variety of ________

Back 31

Posttranslational modifications

Front 32

Some proteins attain their correct conformation only with assistance of one or more of a diverse group of protein ________.

Back 32

Chaperones

Front 33

Chaperones can do all of the following EXCEPT:
A. Stabilize intermediates
B. Maintain proteins in a folded state to allow passage through membranes
C. Help unfold misfolded segments
D. Prevent inappropriate interactions with other proteins

Back 33

B. Maintain proteins in a folded state to allow passage through membranes

They need to be UNFOLDED

Front 34

Proteins destined for export are synthesized on ________

Back 34

Membrane bound ribosomes of the rough ER

Front 35

The ________ is an elongated particle made up of 6 different proteins.

Back 35

Signal Recognition Particle (SRP)

Front 36

The protein is anchored to luminal surface of membrane by an uncleaved ________ with several ________ residues

Back 36

Signal peptide; hydrophobic

Front 37

_______ at the cytoplasmic surface of the ER membrane serves as glycosyl acceptor of N-acetylglucosamine

Back 37

Dolichol phosphate

Front 38

N-glycosylation is ________, meaning it occurs as the protein is being synthesized and can affect protein folding

Back 38

Cotranslational

Front 39

To survive, a living cell must be able to __________ in its environment.

Back 39

Respond to changes

Front 40

The genes that code for the enzymes of a specific metabolic pathway are ________ in one region of DNA

Back 40

Clustered

Front 41

Genes for associated structures are frequently ________ to one another

Back 41

Adjacent

Front 42

The complete regulatory unit of a set of clustered genes

Back 42

Operon

Front 43

Code for the related enzymes or associated proteins

Back 43

Structural genes

Front 44

Code for the regulator protein(s)

Back 44

Regulatory genes

Front 45

Sites on the DNA near the structural genes at which regulator proteins act

Back 45

Control elements

Front 46

Degeneracy of the genetic code denotes the existence of:
A.multiple codons for a single amino acid.
B.codons consisting of only two bases.
C.base triplets that do not code for any amino acid.
D.different systems in which a given triplet codes for different amino acids.
E.Codons that include one or more of the “unusual” bases.

Back 46

A

Front 47

In the formation of an aminoacyl-tRNA:
A.ADP and Pi are products of the reaction.
B.aminoacyl adenylate appears in solution as a free intermediate.
C.aminoacyl-tRNA synthetase is believed to recognize and hydrolyze incorrect aminoacyl-tRNA’s it may have produced.
D.separate aminoacyl-tRNA synthetases exist for every amino acid in the functional protein.
E.there is a separate aminoacyl-tRNA synthetase for every tRNA species.

Back 47

C

Front 48

During initiation of protein synthesis:
A.methionyl-tRNA appears at the A site of the 80 S initiaton complex.
B.eIF-3 and the 40 S ribosomal subunit participate in forming a preinitiation complex.
C.eIF-2 is phosphorylated by GTP.
D.the same methionyl-tRNA is used as is used during elongation.
E.a complex of mRNA, 60 S ribosomal subunit, and certain initiation factors is formed.

Back 48

B

Front 49

During the elongation stage of eukaryotic protein synthesis:
A.the incoming aminoacyl-tRNA binds to the P site.
B.a new bond synthesized by peptidyl transferase requires GTP hydrolysis.
C.the peptidyl-tRNA is translocated to a different site on the ribosome.
D.streptomycin can cause premature release of the incomplete peptide.
E.peptide bond formation occurs by the attack of the carboxyl group of the incoming amino acyl-tRNA on the amino group of the growing peptide chain.

Back 49

C

Front 50

Formation of mature insulin includes all of the following except:
A.removal of a signal peptide.
B.folding in to a three-dimensional structure.
C.disulfide bond formation.
D.removal of a peptide from an internal region.
E.γ-carboxylation of glutamate residues.

Back 50

E

Front 51

Chaperones:
A.are always required to direct the folding of proteins.
B.when bound to protein increase the rate of protein degradation.
C.usually bind to strongly hydrophilic regions of unfolded proteins.
D.sometimes maintain proteins in an unfolded state to allow passage through membranes.
E.foster aggregation of proteins into plaques.

Back 51

D

Front 52

Targeting a protein to be degraded within proteasomes usually requires ubiquitin. In the function of ubiquitin all of the following are true except:
A.ATP is required for activation of ubiquitin.
B.a peptide bond forms between the carboxyl terminal of ubiquitin and an Є-amino group of a lysine.
C.linkage of a protein to ubiquitin does not always mark it for degradation.
D.the N-terminal amino acid is one determinant of selection for degradation.
E.ATP is required by the enzyme that transfers the ubiquitin to the protein to be degraded.

Back 52

E

Front 53

4-Hydroxylation of specific prolyl residues during collagen synthesis requires all of the following except:
A.Fe2+.
B.a specific amino acid sequence at the site of hydroxylation.
C.ascorbic acid.
D.co-hydroxylation of lysine.
E.individual α chains, not yet assembled into a triple helix.

Back 53

D

Front 54

Much of procollagen formation occurs in the endoplasmic reticulum and Golgi apparatus which requires signal peptide. All of the following statements about targeting a protein for the ER are true except:
A.signal peptide usually has a positively charged N-terminus and a stretch of hydrophobic amino acids.
B.signal peptide emerging from a free ribosome, binds signal recognition particle (SRP).
C.signal peptide is usually cleaved from the protein before the protein is inserted into the ER membrane.
D.docking protein is actually an SRP receptor and serves to bind the SRP to the ER.
E.SRP and docking protein do not enter the ER lumen but are recycled.

Back 54

C

Front 55

Streptomycin binds the small subunit of prokaryotic ribosomes and:
A.causes premature release of the incomplete peptide.
B.prevents binding of the 40S and 60S subunits.
C.interferes with initiation of protein synthesis.
D.inhibits peptidyl transferase activity.
E.acts as an N-glycosidase.

Back 55

C

Front 56

Diphtheria toxin:
A.acts catalytically.
B.releases incomplete polypeptide chains from the ribosome.
C.activates translocase.
D.prevents release factor from recognizing termination signals.
E.attacks the RNA of the large subunit.

Back 56

A

Front 57

1.Full expression of the lac operpon requires:
A.lactose and cAMP
B.allolactose and cAMP
C.lactose alone
D.allolactose alone
E.absence or inactivation of the lac operon

Back 57

B

Front 58

2.In an operon:
A.each gene of the operon is regulated independently
B.control may be exerted via induction or via repression
C.operator and promoter may be trans to the genes they regulate
D.the structural genes are either not expressed at all or they are fully expressed
E.control of gene expression consists exclusively of induction and repression

Back 58

B

Front 59

3.The E.coli lacZYA region will be upregulated if:
A.there is a defect in binding of the inducer to the product of the lacI gene
B.glucose and lactose are both present, but the cell cannot bind the CAP protein
C.glucose and lactose are both readily available in the growth medium
D.the operator has mutated so it can no longer bind repressor
E.the lac corepressor is not present

Back 59

D

Front 60

4.All of the following describe an operon except:
A.control mechanism for eukaryote genes
B.includes structural genes
C.expected to code for polycistronic mRNA
D.contains control sequences such as an operator
E.can have multiple promoters

Back 60

A

Front 61

5.In bacteria, amino acid starvation is associated with the production of guanosine tetraphosphate and guanosine pentaphosphate. This situation is referred to as:
A.attenuation
B.corepression
C.repression
D.self-regulation
E.stringent response

Back 61

E

Front 62

6.Tryptophan as a corepressor for the trp operon binds to the:
A.operator
B.promoter
C.repressor protein
D.RNA polymerase
E.upstream region from the promoter

Back 62

C

Front 63

7.In eukaryotic transcription by RNA polymerase II, formation of a preinitiation complex:
A.begins with the binding of a protein (TRB) to the TATA box of the promoter
B.involves the ordered addition of several transcription factors and the RNA polymerase
C.allows an ATP-dependent opening of the two strands of DNA
D.requires that the C-terminal domain of RNA polymerase II not be phosphorylated
E.all of the above are correct

Back 63

E

Front 64

8.Enhancers:
A.are sequences in the promoter that bind to hormone-transcription factor complexes
B.are more effective the closer they are to the TATA box
C.may be thousands of base pairs away from preinitiation complex assembly
D.must be upstream of the site of the preinitiaton complex assembly
E.bind transcription factors that act directly with the initiation complex

Back 64

C

Front 65

9.All of the following phrases describe transposons except:
A.a means for the permanent incorporation of antibiotic resistance into the bacterial chromosome.
B.contain short inverted terminal repeat sequences
C.code for an enzyme that synthesizes guanosine tetraphosphate and guanosine pentaphosphate, which inhibit further transposition
D.include at least one gene that codes for a transposase
E.contain varying numbers of genes

Back 65

C

Front 66

10.In the operation of transposons:
A.typically the transposon moves from its original site and relocates to a different site
B.a duplicated transposon must be inserted into the same DNA molecule as the original
C.all transposons are approximately the same size
D.the insertion sites must be in a concensus sequence
E.the transposase may recognize the repetitive ends of the transposon and participate in the cleavage of the recipient site

Back 66

E

Front 67

11.In chromatin:
A.a nucleosome consists of four molecules of histones surrounding a DNA core
B.DNA positioned so that the major and minor grooves are on the outside of the nucleosome is more accessible for transcription than if the grooves face the interior
C.DNA must be completely removed from the nucleosome structure for transcription
D.linker DNA is the only DNA capable of binding transcription factors
E.the histone octamer consists of eight different kinds of histone proteins

Back 67

B

Front 68

12.Acetylation of histones can lead to a more open DNA structure by:
A.weakening the electrostatic attraction between histones and DNA
B.causing histones to interact with the C-terminal domain (CTD) of RNA polymerase
C.causing electrostatic repulsion between histones and DNA
D.facilitating methylation of DNA
E.attracting transcription factors to DNA

Back 68

A