Translation/Protein Synthesis Flashcards
Prokaryotic ribosomes are a ___ multi-protein, multi-RNA complex, consisting of a large ___subunit (___ proteins + ___ rRNA + ___ rRNA) and a smaller ___ subunit (__ proteins + ___ rRNA).
- 70S
- 50s
- 31 proteins, 23S rRNA, 5s rRNA
- 30s
- 21 proteins, 16s rRNA
___ constitute most of the bulk of ribosomes and catalyze the formation of ___ ___.
- rRNAs
- peptide bonds
Translation is performed by ribosomes on mRNA and occurs in the ___ to ___ direction. The rate of translation in bacteria is about the same as the rate of ___ (___-___ bases or ___-___ amino acids per second).
- 5’ to 3’
- transcription
- 45-50
- 15-17
In translation, the 5’ end of the coding region corresponds to the ___ ___ of the protein. The 3’ terminus of the coding region corresponds to the ___ ___ of the protein.
- amino end
- carboxyl end
As polypeptides are being synthesized the previously synthesized chain is attached to the ___ ___ of the incoming (new) amino acid and the entire complex is, as a result, attached to the ‘new’ ___. Thus, polypeptides are synthesized in the ___ to ___ terminus.
- free amine
- tRNA
- amino to carboxyl
Transcription and translation are coupled together in bacteria, but not in ___. Multiple ___ performing translation on a single mRNA is known as a ___.
- eukaryotes
- ribosomes
- polysome
Prokaryotic (but NOT eukaryotic) mRNAs are often ___ - carrying coding for ___ ___ ___ protein.
- polycistronic
- more than one
Translational accuracy is about ___ error per ___to ___ ___ amino acids. Greater accuracy would ___ translation down, so a ___ is struck between the need for accuracy and the need to synthesize proteins reasonably rapidly.
- one
- thousand to ten thousand
- slow
- balance
tRNAs have extensive ___-___ regions. They are typically ___-___ bases long, with ___ regions at least partly in the __ form.
- self-complimentary
- 73-93
- duplex
- A
The shape of tRNAs is that of an ‘’. At the __ end of the tRNA is usually a ‘’ and at the __ end is a ___.
- ‘L’
- 5’
- ‘G’
- 3’
- CCA
Enzymes that catalyze the linkage of amino acids to tRNA’s __ or __ ends are called ___-___-____ (we nicknamed them “Terry” in class). There are __ of these enzymes - one for each amino acid.
- 3’ or 2’
- aminoacyl-tRNA-synthetases
- 20
Amino acids are linked to tRNAs by ___ bonds between the ___ group of the amino acid and either the ___ or ___ ___of the ___ of the terminal ___ residue of the tRNA. The ester bonds are extremely ___ in water and must be protected from it.
- ester
- carboxyl
- 2’ or 3’ hydroxyl
- ribose
- adenosine
- unstable
The anticodon loop has ___ bases complementary to the codon in the mRNA. tRNAs provide the ___ function between nucleic acid sequence and ___ ___.
- three
- translation
- amino acids
The anticodon loop frequently contains the ___ ___. The base at the ___ end of the codon of the mRNA (corresponds to the base at the 5’ end of the anticodon in the tRNA) is called the ___ ___ because it is ___ ___ for specifying the amino acid to be inserted than the first two bases.
- inosine base
- 3’
- wobble base
- less important
Aminoacyl-tRNA synthetases have the ability to ___ and ___ errors in joining of amino acids to tRNAs. For example, if one puts the wrong amino acid on the end of a tRNA and then adds an appropriate ___-___ ___, the amino acid is readily removed.
- recognize
- correct
- aminoacyl-tRNA synthetase
Two regions of aminoacyl-tRNA synthetases are important for editing - called the ___ site (also called the ___ site) and the ___ site.
- activation
- acylation
- editing
There are two classes of amino acid tRNA ___. They differ in the way they bind ___ and in which ___ of the ___ ___ they attach the amino acid to.
- synthetases
- tRNAs
- hydroxyl
- ribose ring
Class I enzymes attach the amino acid to the:
Class II enzymes attach the amino acid to the:
- hydroxyl on carbon #2.
- hydroxyl on carbon #3.
Base pairings in RNA are slightly different than in DNA. For example, - base pairs are not unstable. In addition, as will be seen later, I can pair with ,, or _.
- G-U
- C, U, or A
In the genetic code, there are ___ possible combinations of the bases of the codon. Three of the possibilities (___, ___, and ___) are used as ‘stop’ codons. They tell the ribosomes where to stop making protein. A start codon (___).
- 64
- UAA, UGA, UAG
- AUG
Ribosomes have three sites for binding/holding/releasing tRNAs. They are called the ,, and _ sites, corresonding to the order in which tRNAs move through them (except for the ___ ___ one).
- A, P, E
- very first
The ___-___ sequence (___) is located near the ___ start codon in prokaryotic sequences. It is complementary to a sequence in the ___ rRNA and serves to help align the ribosome with the ___ site for translation in prokaryotes.
- Shine-Delgarno
- GGAGG
- AUG
- 16S
- start
In prokaryotes, the first amino acid incorporated into a protein is a ___ form of methionine called ___. The formyl group is put onto methionine ___ it is in the tRNA by a ___ enzyme
- formylated
- fMet
- after
- transformylase
Formylation of methionine in prokaryotes ___ the otherwise free amino end from ___ intramolecularly and ___ transcription.
- protects
- reacting
- terminating
Peptides exit the ribosome as they are being synthesized via a ___ in the structure.
-tunnel
Initiation of protein synthesis starts with binding of ___ and ___ to the ___ ribosomal unit. The mRNA is aligned with the ___ ___ site.
- IF1
- IF3
- 30s
- Shine-Delgarno
IF2 (when bound to GTP) acts to carry the ___-___ to the ___ ___ of the 30S subunit and base pairs it with the ___ ___ codon.The complex of mRNA, IF1, IF2, and Met-tRNAf is called the ___ ___ ___.
- Met-tRNAf
- P site
- AUG start
- 30S initiation complex
Hydrolysis of the ___ in ___ results in release of the ___ and ___ from the initiation complex. That, coupled with binding of the ___ subunit yields the 70S initiation complex with Met-tRNAf in the ___ ___ and the A and E sites open.
- GTP
- IF2
- IF2 and IF1
- 50s
- P-site
The process of elongation begins on the ___ ___ ___. ___ (a G protein coupled to GTP) carries a ___ tRNA to the ___ ___ of the complex. If the tRNA anti-codon base pairs properly with the codon in the mRNA, it stays matched with the codon and GTP is ___ on EF-Tu and ___ ___ is released.
- 70s initiation complex
- EF-Tu
- charged
- A site
- hydrolyzed
- EF-Tu GDP
If the tRNA anti-codon does not form a stable base pairing with the complex, the entire charged ___-___-___ complex ____.
- tRNA-EF-Tu-GTP
- dissociates
Next, the ___ group on the tRNA in the ___ ___ is transferred and ___ linked via peptide bond to the amino acid on the tRNA in the ___ ___. This reaction is catalyzed by an enzymatic activity called ___ - a ribozyme activity of the ___ rRNA in the ___ subunit.
- peptide
- P site
- covalently
- A-site
- peptidyltransferase
- 23S, 50S
The tRNA in the A site along with the peptide it is covalently attached to is transferred to the ___ ___ as the “___” tRNA in the P site is moved to the ___ ___
- P site
- empty
- E site
EF-G-GTP is involved in the process and ___ is ___ in the process. EF-G-GTP has a similarity to the ___-___-___ complex and may act to displace it.
- GTP
- hydrolyzed
- tRNAaminoacid-EF-Tu-GTP
As the old tRNA is released from the ___ ___, the empty A site accepts the ___ ___ corresponding to the next codon. The net result of one turn of this cycle is that the polypeptide has grown by ___ ___ ___ residue and the ribosome has moved along the ___ by ___ nucleotide residues. The process is repeated until a ___ signal is reached.
- E- site
- aminoacyl tRNA
- one amino acid
- mRNA
- three
- termination
The process of translation ___ begins when a stop codon appears in the ___ ___ of the ribosome. Termination of translation requires action of ___ ___ (___, ___)
- termination
- A-site
- release factors
- RF1, RF2
RF-1 and RF-2 carry ___ to the ___ ___.The ___ ___ transfers the polypeptide on the tRNA in the ___ ___ to water, thus ___ the completed polypeptide from the ribosome.
- water
- A site
- peptidyl transferase
- P site
- releasing
Translational diffs in eukaryotes relate to the structure of eukaryotic cells. Targeting of proteins to organelles, the membrane, or outside of the cell, starts during ___ ___. Proteins destined to leave the cytoplasm have a ___ ___, consisting of a stretch of ___ amino acids near their ___ terminus.
- protein synthesis
- signal sequence
- hydrophobic
- amino
When the ___ sequence emerges from the ribosome during translation, it is recognized by the ___ ___ ___ (___), which takes the entire ___/___/___ complex to the endoplasmic reticulum.
- signal
- signal recognition particle
- SRP
- ribosome/mRNA/polypeptide
At the ER it interacts with the ___ ___ and in the process it links the ___ with the emerging polypeptide sequence to the ___.
- SRP receptor
- ribosome
- translocon
The polypeptide passes through the ___ channel as it is being made and when the signal sequence completely exits the translocon, a ___ ___ clips it free of the rest of the polypeptide. The translation process continues until the ___ ___ is reached and then everything releases from the ___.
- translocon
- signal peptidase
- stop codon
- translocon
The polypeptide remains in the ___ ___ where it is further process to travel to the ___ for additional ___ and ___. Other sequences in the polypeptide may help to direct modifications and/or the final ___ of the mature protein.
- Endoplasmic reticulum
- Golgi
- processing and targeting
- destination
Antibiotics frequently are designed to target various aspects of translation. They include ___ (interferes with binding of ___ tRNA to ribosome), ___ (inhibits binding of ___-___), ___ (inhibits ___ ___ activity), and ___ (causes premature ___ ___).
- streptomycin (formylmethionyl)
- tetracytline (aminoacy-tRNAs)
- chloramphenical (peptidyl-transferase)
- puromycin (chain termination)
