02/20 translation Flashcards
How many ribosomes are in prokaryotes?
one ribosome, 70S
Where is the ribosome for prokaryotes found
in the cytoplasm
How many ribosomes are in eukaryotes
there are two ribosomes
what are the two types of ribosomes in eukaryotes
One of them is in the cytoplasm (80S), and the other is found in organelles like the mitochondria. it is 70S and acts like a prokaryotic ribosome
what is the difference between the two ribosomes in eukaryotes
the 80S is eukaryotic functioning and the other is 70S and found in the mitochondria, it acts like a bacterial ribosome
what are the subunits for bacterial ribosomes?
larger subunit: 50S and smaller subunit is 30S
true or false, the holocomplex for the bacterial ribosome is 80S
false, the subunits are not additive and instead. meld together to form 70S
where are the ribosomes for eukaryotic organisms found
in the cytoplasm outside the nucleus
what are the subunits of the eukaryotic ribosome
the 40s and 60s
what is the holocomplex of the eukaryotic ribosome
the 80S
what RNA is important in the small subunits of bacterial and eukaryotic ribosomes
16sRNA in p and 18sRNA in e
what type of ribosome is found in the mitochondria
70S, the bacterial ribosome due to its circular DNA
what are the three critical ribosome sites
P site (peptidyl)
A site ( aminoacyl site)
E site (Exit site)
where does the charged tRNA enter
the A site
where is the growing polypeptide chain
the P site
after the tRNA in the P site has transferred its polypeptide chain and translocates to the E site, what happens to the uncharged tRNA
it leaves the ribosome to be recharged by aminoacyl tRNA synthetase
go review the process lol
where is the first initiator tRNA added
it is added at the P site, this is the only one that does this
in bacterial translation, what is the purpose of the 5’ UTR?
it is the ribosomal binding site
initially, the ribosome subunits are
uncoupled
what does the stop codon do
a release factor (protein) will bind at the A site, not an amino acid
what is post-translational modification
the polypeptide will form its tertiary structure and may be modified
as the polypeptide chain is formed, does it remain in its primary state
no, it begins its secondary folding immediately
What is the role of the 16aRNA component of the 30s subunit?
it binds complementary to the mRNA ribosomal binding site and attaches the mRNA to the 30s subunit
does the 18sRNA component of the 40s RNA in eukaryotes bind to the ribosomal binding site
no, there is no ribosomal binding site
how does the first tRNA bind at the P site and not the A site?
the initiation factors bind to the smaller subunit and block the E and A sites so only the P site can b accessed
after the mRNA binds to the 30S ribosomal subunit and the initiation factors bind, what occurs
the initiator tRNA binds at the P site followed by the larger 50S subunit
True or false; both prokaryotic and eukaryotic translation initiation uses the small unit of the ribosome to bind to a ribosomal binding sequence near the start codon
false
only prokaryotics do this. Eukaryotics have a scanning process where the ribosome seeks out the best AUG start codon after attaching to the 5’ Cap
how is initiation of trnaslationdifferent for eukaryotic cells
the ribosome will attach through the 5’ cap and scan through the 5’ UTR until it finds an AUG with a good consensus sequence
is every AUG considered a start codon in eukaryotic translation
no, usually the start AUG codon is the first one after the 5’ cap but it depends on the consensus sequence
what are kozak rules
usually the start codon is the first AUG after the 5’ cap but there is an optimal consensus sequence
which has a faster elongation process
prokaryotes are generally faster
what energy source is used for elongation of polypeptides
GTP
what creates the covalent bond between the previous polypeptide chain and the new amino acid
peptidyl transferase forms a peptide bond
what is the peptidyl transferase
it is a ribozyme on the large ribosomal subunit, it forms a peptide covalent bond
if a protein was boiled, what happens to the covalent bonds (e.g, cysteine disulfide bridges)
they remain intact
what is the reading frame
The reading frame describes how everything downstream of the AUG start codon is read in NON overlapping sets of 3
what is the high fidelity of translation determined by
the proper charging of tRNA through tRNA synthetase and its covalently modified bases and through anti-codon/ codon matching
What are the nonsense/ stop codons
they are codons that are not recognized by tRNAs but rather are recognized by release factor proteins that bind in the A site
where do release factor proteins bind in the ribosome
they bind in the A site of the ribosome
what is a polyribosome
an mRNA transcript with many bound ribosomes performing translation
what organisms can form polyribosomes
both prokaryotes and eukaryotes
what is coupling
coupling is the process where translation begins before transcription is done IN BACTERIA
THIS DOESNT OCCUR IN EUKARYOTES
can eukaryotes couple transcription and tranlsation
no! only prokaryotes
