Protein synthesis Flashcards
proteins are synthesized at the ____
ribosome
During the process of translation, proteins are synthesized at the ____ by linking ___ ____ together in the order specified by the sequence of codons in mRNA
ribosome, amino acids
prokaryotes are know as the ____S ribosomes
70
eukaryotes are known as the ___S ribosomes
80
what are the two parts of the prokaryotic ribosomes?
30S, 50S
what are the two parts of the eukaryotic ribosomes?
40S, 60S
a prokaryote can contain ____ ribosomes and a eukaryote can contain _____
20,000, 200,000
what percent rRNA is the small pro subunit (30S)?
60
what percent rRNA is the large pro subunit (50S)?
70
what percent rRNA is the small euk subunit (40S)?
50
what percent rRNA is the large euk subunit (60S)?
65
What are the three phases of protein synthesis?
initiation, elongation, and termination
Involves binding of mRNA to the small and large ribosomal subunits, and binding of an initiator tRNA
initiation
Includes the formation of all peptide bonds of the growing polypeptide chain.
elongation
Occurs when a “stop” codon is reached along the mRNA, which leads to the release of the completed polypeptide.
termination
what is the purpose of the gap between the ribosomal subunits?
mRNA goes through, RNA, growing protein chain
where does the new amino acid bind to the ribosome?
A site
at what site does the growing polypeptide growing?
P site
at what site is the exit site for tRNA
E site
what holds the growing chain to the P site?
the anticodon and tRNA
pro: EF-Tu
eEf1(alpha)
pro: EF-Ts
eEF1(beta)(gamma)
pro: EF-G
eEF2
what is the eukaryotic release factor?
eRF1
what are the prokaryotic release factors?
RF-1, RF-2, RF-3
initiation begins with the binding of ____ and the ___ _____ to the 30S ribosomal subunit
mRNA, initiator tRNA
all other parts of the growing chain attach to the ___ site except for the initiator, which attaches to the ___ site
A, P
what happens to GTP during initiation?
breaks down into GDP
what it the anticodon sequence of f-met-tRNA?
5’CAU3’
The 70S initiation complex consists of the __ and __ ribosomal subunits, mRNA, and the initiator tRNA bound to the P site
30S and 50S
The mRNA and ___ are in the gap between the two subunits
tRNA
What else is involved in the initiation of protein synthesis?
The initiation factors IF-1, IF-3, IF-2, and GTP
are also required
The initiator ___ binds to the P
site on the 30S subunit, and the
___ subunit joins the 30S subunit
tRNA, 50S
The initiator tRNA of E coli is
f-Met-tRNA
during peptide chain elongation, the first stage is the binding of a new ______ to the A site
aminoacyl-tRNA
what elongation factor brings about the binding of a new aminoacyl-tRNA to the A Site?
EF-Tu
what elongation factor recycles EF-Tu after it binds an aminoacyl-tRNA?
EF-Ts
the ____ _____ activity is not due to a protein enzyme, but is due to an RNA enzyme activity of the peptidyl transferase center of the 23S rRNA and the 50S subunit
peptidyl transferase
translocation of the peptide chain back to the P site is brought about by elongation factor _____
EF-G
Peptidyl transfer is the step that forms the ___ ___ between the new amino acid and the growing polypeptide chain
peptide bond
The elongation cycle requires what three factors?
EF-Tu, EF-Ts, EF-G
activated EF-TU is required for aminoacyl-tRNA to bind, and it is activated by ____
GTP
____ is the second enzyme in addition to EF-TU that needs to be activated by GTP
EF-G
The binding of release factors to the A site transforms
the ___ ___ ___, that forms the peptide bond between amino acids, into a hydrolase.
ribosomal peptidyl transferase
The peptidyl transferase then ____ the bond
linking the polypeptide to its tRNA carrier, thereby
releasing the polypeptide
hydrolyzes
the presence of a ___ ____ at the A site brings about the binding of 2 release factors to the A site (always at lease RF-3) along with GTP
stop codon
the biding of release factors to the A site transforms the ribosomal peptydyl transferase into a ____, which breaks covalent bonds
hydrolase
after dissocitation, there is ___ ____ between the pool of 50S ribosomes and 30S ribosomes
dynamic equillibrium
a ____ is multiple ribosomes synthesizing proteins on a single mRNA molecule
polysome
prokaryotic mRNAs can have up to _____ ribosomes attached
10
what are Hsp70, GroES/GroEL exmaples of?
molecular chaperones that aide in the folding of proteins into the cell
_____ percent of proteins require GroES/GroEL to fold (all else requires either none or Hsp70)
15 %
After the 70S ribosomes dissociate from the mRNA, the ribosomes separate into free __ and ___ subunits
30S and 50S
