BCH5413 Exam 3 ACTUAL Exam Questions and
CORRECT Answers
The ribosome consists of both ribosomal RNA and ribosomal proteins.
Which part primarily determines the shape of the ribosome - ANSWER
-The structure of the ribosome is dependent on the ribosomal RNA and
how they might base pair with each other at different segments.
The ribosome consists of both ribosomal RNA and ribosomal proteins.
Which part contains the peptidyl transferase activity? - ANSWER -The
50S subunit (large subunit) contains the peptidyl transferase activity.
The ribosome consists of both ribosomal RNA and ribosomal proteins.
Which part contains the GTP hydrolysis activity? - ANSWER -The 50S
subunit (large subunit) contains GTPase activity.
During protein synthesis, what kind of bond joins the amino acids?
Which parts (functional groups) of the amino acids are bonded together?
- ANSWER -The 50S subunit links amino acids together through
peptide bonds. Amino acids connect to form a peptide bond through a
reaction between the amino group and carboxyl group. A peptide bond is
formed through a dehydration reaction. This involves the removal of two
hydrogens and an oxygen.
,tRNA Charging: How does the aminoacyl-tRNA synthetases recognize
which tRNA gets its amino acid? - ANSWER -Recognition will depend
on nucleotides within the tRNA and binding sites within the protein.
tRNA Charging: Describe the 2-step process for charging the tRNA. -
ANSWER -The first step is the activation of the amino acid with the
help of ATP to form aminoacyl-AMP. The second step will use the
energy from the aminoacyl-AMP bond to transfer the amino acid onto
the acceptor stem of the tRNA.
tRNA charging: Where does the amino acid get added to the tRNA? Be
specific about the end of the RNA and the position of binding on the
RNA. - ANSWER -The high-energy bond between the aminoacyl and
AMP will be used to transfer the amino acid to the 3' end of the tRNA;
specifically, the amino acid will form an ester bond between the
3'carbon hydroxyl group on the adenosine of the tRNA and the carboxyl
group of the amino acid.
What is the wobble hypothesis? What is its significance? - ANSWER
The wobble hypothesis is: The 3rd position base on a codon which is
allowed to be different to accommodate different tRNA, this exception
allows it to form a non Watson-Crick base pair with the anticodon.
This is significant because the wobble allows some aminoacyl-tRNAs to
pair with more than one codon
True/False: Protein synthesis requires GTP. - ANSWER -TRUE, When
binding an aminoacyl-tRNA to the A site
, True/False: Wobble allows the different aminoacyl-tRNA to pair with
same codon. - ANSWER -TRUE, 3rd base of a codon is allowed to
move slightly from it snormal position, allowing same
aminoacryltRNAs to pair with more than one codon
True/False: Ligase enzyme joins the amino acids to the respective
tRNAs - ANSWER -FALSE, AA attached by ester bond between 2'-OH
of terminal adenosine of tRNA
True/False: Aminoacylation of tRNAs requires GTP - ANSWER
FALSE, 2 step process reuire AMP from ATP to activate AA, then,AMP
is used to transfer the AA to tRNA
True/False: Fmet-tRNA is the initiator tRNA in Eukaryotes -
ANSWER -FALSE, N-Formylmethionine=Fmet-tRNA is the initiator of
Prokaryotes
What differences are there between the ribosome binding in prokaryotes
vs. eukaryotes? - ANSWER -During translation in prokaryotes, the
ribosome binds an operon at a ribosome binding site that precedes an
open reading frame. Once the ribosome binds, there are various soluble
factors that ensure the ribosome reads the correct code to make the
correct protein.During translation in eukaryotes, the ribosome binds the
5' cap, then scans the mRNA for the AUG start site. The ribosome also
requires soluble factors to initiate translation.
What is the function of IF1? - ANSWER -binds to the A site and keeps
the fmet-tRNA from binding there
, What is the function of IF2? - ANSWER -binds to the fmet-tRNA and
GTP and brings the complex to the P site
What is the function of IF3? - ANSWER -binds to 30S subunit to keep
it separate from the large subunit
What is the function of hydrolysis of GTP after 70s initiation complex
is formed? - ANSWER -releases IF2 and GDP from the complex so
polypeptide chain elongation can begin
Explain the three steps in formation of 70s complex. - ANSWER -The
ribosome first dissociates. The 30S initiation complex is the first to
form. IF3 binds to the 30s ribosome to prevent reassociation of the 2
ribosomal subunits. With the assistance of IF1 and IF2, IF3 binds to the
Shine-Delgarno sequence (RBS) on the 5' end mRNA. This sequence is
also recognized by a complementary sequence in the 16S rRNA.. IF2
will bind to the fmet-tRNA and to GTP and bring them to the P-site. No
GTP hydrolysis occurs at this point. IF3 will leave the 30S initiation
complex, allowing the 50S subunit to join the complex. At this point,
GTP is hydrolyzed by the GTPase of the 50S subunit. This hydrolysis
allows the release of IF2 (and GDP), leaving the fmet-tRNA in the Psite.
At this point the 70S complex is complete and elongation can begin.
Explain the three main steps of elongation. Be sure to indicate when
GTP is needed and why. - ANSWER -Once the 30S initiation complex
is formed, IF3 comes off, allowing 50S subunit to bind. When 50S joins
the 30S complex GTP is hydrolyzed to form 70S complex. GTP
hydrolysis is carried out by GTPase in 50S subunit. The purpose of
CORRECT Answers
The ribosome consists of both ribosomal RNA and ribosomal proteins.
Which part primarily determines the shape of the ribosome - ANSWER
-The structure of the ribosome is dependent on the ribosomal RNA and
how they might base pair with each other at different segments.
The ribosome consists of both ribosomal RNA and ribosomal proteins.
Which part contains the peptidyl transferase activity? - ANSWER -The
50S subunit (large subunit) contains the peptidyl transferase activity.
The ribosome consists of both ribosomal RNA and ribosomal proteins.
Which part contains the GTP hydrolysis activity? - ANSWER -The 50S
subunit (large subunit) contains GTPase activity.
During protein synthesis, what kind of bond joins the amino acids?
Which parts (functional groups) of the amino acids are bonded together?
- ANSWER -The 50S subunit links amino acids together through
peptide bonds. Amino acids connect to form a peptide bond through a
reaction between the amino group and carboxyl group. A peptide bond is
formed through a dehydration reaction. This involves the removal of two
hydrogens and an oxygen.
,tRNA Charging: How does the aminoacyl-tRNA synthetases recognize
which tRNA gets its amino acid? - ANSWER -Recognition will depend
on nucleotides within the tRNA and binding sites within the protein.
tRNA Charging: Describe the 2-step process for charging the tRNA. -
ANSWER -The first step is the activation of the amino acid with the
help of ATP to form aminoacyl-AMP. The second step will use the
energy from the aminoacyl-AMP bond to transfer the amino acid onto
the acceptor stem of the tRNA.
tRNA charging: Where does the amino acid get added to the tRNA? Be
specific about the end of the RNA and the position of binding on the
RNA. - ANSWER -The high-energy bond between the aminoacyl and
AMP will be used to transfer the amino acid to the 3' end of the tRNA;
specifically, the amino acid will form an ester bond between the
3'carbon hydroxyl group on the adenosine of the tRNA and the carboxyl
group of the amino acid.
What is the wobble hypothesis? What is its significance? - ANSWER
The wobble hypothesis is: The 3rd position base on a codon which is
allowed to be different to accommodate different tRNA, this exception
allows it to form a non Watson-Crick base pair with the anticodon.
This is significant because the wobble allows some aminoacyl-tRNAs to
pair with more than one codon
True/False: Protein synthesis requires GTP. - ANSWER -TRUE, When
binding an aminoacyl-tRNA to the A site
, True/False: Wobble allows the different aminoacyl-tRNA to pair with
same codon. - ANSWER -TRUE, 3rd base of a codon is allowed to
move slightly from it snormal position, allowing same
aminoacryltRNAs to pair with more than one codon
True/False: Ligase enzyme joins the amino acids to the respective
tRNAs - ANSWER -FALSE, AA attached by ester bond between 2'-OH
of terminal adenosine of tRNA
True/False: Aminoacylation of tRNAs requires GTP - ANSWER
FALSE, 2 step process reuire AMP from ATP to activate AA, then,AMP
is used to transfer the AA to tRNA
True/False: Fmet-tRNA is the initiator tRNA in Eukaryotes -
ANSWER -FALSE, N-Formylmethionine=Fmet-tRNA is the initiator of
Prokaryotes
What differences are there between the ribosome binding in prokaryotes
vs. eukaryotes? - ANSWER -During translation in prokaryotes, the
ribosome binds an operon at a ribosome binding site that precedes an
open reading frame. Once the ribosome binds, there are various soluble
factors that ensure the ribosome reads the correct code to make the
correct protein.During translation in eukaryotes, the ribosome binds the
5' cap, then scans the mRNA for the AUG start site. The ribosome also
requires soluble factors to initiate translation.
What is the function of IF1? - ANSWER -binds to the A site and keeps
the fmet-tRNA from binding there
, What is the function of IF2? - ANSWER -binds to the fmet-tRNA and
GTP and brings the complex to the P site
What is the function of IF3? - ANSWER -binds to 30S subunit to keep
it separate from the large subunit
What is the function of hydrolysis of GTP after 70s initiation complex
is formed? - ANSWER -releases IF2 and GDP from the complex so
polypeptide chain elongation can begin
Explain the three steps in formation of 70s complex. - ANSWER -The
ribosome first dissociates. The 30S initiation complex is the first to
form. IF3 binds to the 30s ribosome to prevent reassociation of the 2
ribosomal subunits. With the assistance of IF1 and IF2, IF3 binds to the
Shine-Delgarno sequence (RBS) on the 5' end mRNA. This sequence is
also recognized by a complementary sequence in the 16S rRNA.. IF2
will bind to the fmet-tRNA and to GTP and bring them to the P-site. No
GTP hydrolysis occurs at this point. IF3 will leave the 30S initiation
complex, allowing the 50S subunit to join the complex. At this point,
GTP is hydrolyzed by the GTPase of the 50S subunit. This hydrolysis
allows the release of IF2 (and GDP), leaving the fmet-tRNA in the Psite.
At this point the 70S complex is complete and elongation can begin.
Explain the three main steps of elongation. Be sure to indicate when
GTP is needed and why. - ANSWER -Once the 30S initiation complex
is formed, IF3 comes off, allowing 50S subunit to bind. When 50S joins
the 30S complex GTP is hydrolyzed to form 70S complex. GTP
hydrolysis is carried out by GTPase in 50S subunit. The purpose of
