BCH5413 EXAM 3 WITH ALL QUESTIONS AND
ANSWERS
What are the subunits of 70s and 80s ribosomes and their main
functions? - ANSWER 70S has two subunits : 30S is the small submit
that decodes mRNA and 50S is the subunit links amino acids together
through peptide bonds
80S has two subunits: 40S and 50S:
40S small subunit, analogous to the 30S subunit in the prokaryotic
ribosome
60S large subunit, analogous to the 50S subunit in the prokaryotic
ribosome
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
aminoacryl-tRNAs 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
ANSWERS
What are the subunits of 70s and 80s ribosomes and their main
functions? - ANSWER 70S has two subunits : 30S is the small submit
that decodes mRNA and 50S is the subunit links amino acids together
through peptide bonds
80S has two subunits: 40S and 50S:
40S small subunit, analogous to the 30S subunit in the prokaryotic
ribosome
60S large subunit, analogous to the 50S subunit in the prokaryotic
ribosome
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
aminoacryl-tRNAs 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
