Chapter 8 Flashcards
In translation, mRNAs are read in the ____ direction, and polypeptide chains are synthesized from the ____ ends.
a. 5’ to 3’; carboxyl to the amino
b. 5’ to 3’; amino to the carboxyl
c. 3’ to 5’; carboxyl to the amino
d. 3’ to 5’; amino to the carboxyl
e. None of the above
b. 5’ to 3’; amino to the carboxyl
Aminoacyl tRNA synthetases are enzymes that
a. synthesize transfer RNAs.
b. attach amino acids to specific transfer RNAs.
c. connect amino acids together while they are held in place on ribosomes by transfer
RN As.
d. attach the terminal CCA sequence to transfer RNAs.
e. attach tRNAs to ribosomes.
b. attach amino acids to specific transfer RNAs.
During translation, the codons on the mRNA are recognized by complementary base pairing to the anticodon on the
a. ribosome.
b. transfer RNA.
c. small cytoplasmic RNA.
d. aminoacyl tRNA synthetase.
e. signal recognition particle.
b. Transfer RNA.
E. coli contains about ___ different tRNAs that code for ___different amino acids.
a. 62;40
b. 62;20
c. 50;20
d. 40;20
e. 20; 16
40;20
The capacity for some tRNAs to recognize more than one codon in mRNA is explained by a phenomenon called
a. a reading mistake.
b. redundancy.
c. wobble.
d. a reading frameshift.
e. degeneracy.
c. wobble
Prokaryotic and eukaryotic ribosomes are
a. the same size.
b. 30S and SOS, respectively.
c. 40S and 60S, respectively.
d. 70S and 80S, respectively.
e. 80S and 90S, respectively.
d. 70S and 80S, respectively.
Which of the following statements is (are) true and provide(s) evidence that a certain component of the ribosome catalyzes protein synthesis?
a. Ribosomes are inactive after protease digestion.
b. Ribosomes are inactive after RNase digestion.
c. Structural analysis shows that proteins occupy the catalytic site where peptide bonds are formed.
d. Structural analysis shows that rRNA occupies the catalytic site where peptide bonds are formed.
e. Both b and d
f. Both b and c
e. Both b and d
Translation of mRNAs starts at
a. the 3’ end of the mRNA.
b. a site downstream of a 3’ untranslated region.
c. the 5’ end of the mRNA.
d. a site downstream of a 5’ untranslated region.
e. the cap structure.
d. a site downstream of a 5’ untranslated region.
Eukaryotic ribosomes recognize and initially bind to what structure on the mRNA?
a. A Shine-Dalgarno sequence
b. The 7-methylguanosine cap
c. A TAT A sequence
d. An AUG initiation codon
e. A CAT sequence.
b. The 7-methylguanosine cap
The first step in the initiation of protein synthesis is the binding of ___ to the
a. initiation factors; initiation codon
b. initiation factors; small ribosomal subunit
c. the small ribosomal subunit; initiation codon
d. the initiator tRNA; initiation codon
e. initiation factors; large ribosome subunit
b.initiation factors; small ribosomal subunit
The first amino acid that initiates the eukaryotic polypeptide is which of the following? a. Any amino acid b. Glutamine c. Methionine d. N-formylmethionine e. Arginine
c. Methionine
Termination of translation and release of the polypeptide chain occurs when
a. tRNA binds to a termination codon via a complementary anticodon but lacks an amino
acid.
@a protein release factor binds to the termination codon.
c. a tRNA with a complementary anticodon binds to a termination codon, and a release
factor bound to the CCA end releases the chain.
d. a small molecule shaped like puromycin binds to the termination codon.
e. Ef-TU binds to the termination codon.
b. a protein release factor binds to the termination codon.
The correctly folded three-dimensional configuration of a protein is determined primarily by the
a. sequence of nucleotides of its gene.
b. primary sequence of its amino acids.
c. chaperones with which it interacts.
d. pathway by which it folds.
e. All of the above
b. primary sequence of its amino acids.
Proteins that facilitate the folding of other proteins are called
a. foldases.
b. binding proteins.
c. chaperones.
d. escorts.
e. BIPs.
c. chaperones.
A signal peptidase
a. removes a signal sequence from a polypeptide chain after it passes through a channel into the rough ER.
b. attaches a signal sequence to a growing polypeptide chain before it passes into the rough ER.
c. attaches an acetyl group to the 5’ end of a polypeptide after removal of the initial methionine.
d. removes the initial methionine from a polypeptide chain.
e. removes a signal sequence from a polypeptide chain before it passes through a channel into the rough ER.
a. removes a signal sequence from a polypeptide chain after it passes through a channel into the rough ER.
In a major protein degradation pathway, a short polypeptide called _____ is attached to a protein to target it for destruction.
a. glutathione
b. ubiquinone
c. Ubbiquitin
d. KDEL
e. protease
c. ubiquitin
A proteasome is a
a. vesicle containing proteolytic enzymes.
b. precursor to lysosomes.
c. complex of a proteolytic enzyme and the protein that is being degraded.
d. multisubunit protease complex that degrades proteins marked for destruction.
e. type of lysosome.
d. multisubunit protease complex that degrades proteins marked for destruction.
Degradation of cytoplasmic organelles occurs by fusion of lysosomes with structures called
a. secondary lysosomes.
b. phagolysosomes.
c. Autophagosomes.
d. mitochondria.
e. primary lysosomes.
b. phagolysosomes
Which of the following statements regarding tRNAs is false?
a. tRNAS are approximately 70-80 bases long and form a cloverleaf structure.
b. All tRNAs have a CCA sequence at their 3’ terminus.
c. tRNAs differ in sequence only at the anticodon.
d. There are several modified bases present in mature tRNAS.
c. tRNAs differ in sequence only at the anticodon.
Signal sequences are sequences of hydrophobic amino acids that target membrane translocation. Signal sequences are found
a. at the amino terminus of the secreted protein.
b.at the carboxy terminus of the secreted protein.
c. on the cytoplasmic side of the membrane channel proteins.
d. on the amino terminus of the 28S of certain ribosomal complexes associated with
secretion.
a. at the amino terminus of the secreted protein.
The adapters that align amino acids in a sequence determined by the mRNAs are called _____
tRNA
Prokaryotic ribosomes differ from eukaryotic ribosomes in that their large and small subunits are ____ and ____, rather than 60S and 40S.
50s; 30s
True or False: A single mRNA can code for more than one polypeptide chain.
True
True or False: Eukaryotic mRNAS have a 7-methylguanosine cap on their 3’ end.
False
