Term
| Polypeptide synthesis takes place where and to what degree...and how? |
|
Definition
| Takes place on ribosomes....thousands of ribosome are in each cell. Ribosomes bind to mRNA and then tRNA binds to mRNA so a polypeptide chain can be synthesized. |
|
|
Term
| what do ribosomes consist of? |
|
Definition
large and small subunits a complex between RNA molecules and proteins.
Each subunit contains rRNA molecules.
Proks ribosomes have 3 r RNA molecules = 23S rRNA 5S rRNA in the large and 16S rRNA in the small.
Euks ribosome have 4 r RNA molecules= the 28 S rRNA, 5.89S rRNA 5S rRNA in the large ....and 18S rRNA in the small. and 18S in the large... rRNA is important in structure and function in translation |
|
|
Term
| Translation in the ribosome |
|
Definition
| mRNA passes through the small sub unit specifice sites of the ribosome bind tRNA at different states of polypeptide synthesis |
|
|
Term
| Specify the sites of the ribosome that bind tRNA at different stages of polypeptide synthesis |
|
Definition
A ( aminoacyl ) site = incoming aminoacyl - tRNA binds.
the P ( peptidyl ) site = tRNA carrying the growing chain is located.
E (exit) site = tRNA binds on the path from the P site to leave the ribosome
The P and A sites have regions of both large and small subgroups
E site in only on the large subunit. |
|
|
Term
| in proks and euks the area of DNA where ribosome genes are located is called |
|
Definition
rDNA or rDNA transcriptions units.
Proks have 7 one copy of 16S 23S and 5F rRNA with a single promoter for each rRNA and tanscription by RNA polymerase..with spacers
Euks have lots of copies of the four rRNA 18S 5.8 s and 5 S clusters of repeat sequences...the fourth is encoded by a seperate gene
|
|
|
Term
| translation begins at the _____, AUG, a few bases downstream of the___________. The AUG specifies methionine. In bacteria, a special initiator tRNA brings formylmethionine (fMet)–methionine modified by the addition of a formyl group–to the mRNA. The anticodon of this initiator tRNA complements AUG. The initiator fMet-tRNA is brought to the 30S subunit–mRNA complex by IF-2, which also carries a molecule of GTP. The result is the ______________________. |
|
Definition
start codon
ribosome-binding site
30S initiation complex |
|
|
Term
| Lastly in initiation of translation, the large ribosomal subunit (50S subunit) binds to the 30S initiation complex, GTP is hydrolyzed and IF-1, IF-2, and IF-3 are released. The final complex is called the ______complex. The fMet-tRNA is now situated________ , with its anticodon hydrogen bonded to the mRNA start codon. Initiation is now complete, and ___________follows. |
|
Definition
70S initiation
in the P site of the ribosome
elongation |
|
|
Term
When translation initiation is complete,
elongation begins.
The elongation phase consists of 3 steps: 1. binding of a ____to the _______, 2. formation of _____________ and ________________. Elongation continues one codon at a time until a stop codon is reached. |
|
Definition
tRNA
ribosome
a peptide bond between adjacent amino acids,
movement of the ribosome to the next codon |
|
|
Term
As initiation concluded, fMet–tRNA was _____
to AUG in the ___site of the ribosome.
The next codon is in ___the site. |
|
Definition
|
|
Term
| With a tRNA in both the P and A sites, a peptide bond can form between adjacent _______. This reaction is catalyzed by peptidyl transferase residing in the large ribosomal subunit. The first step involves breaking the bond ____________ Next, a peptide bond forms between the now-freed fMet and the serine(or whatever AA is next) which is attached to its ____________ |
|
Definition
amino acids
between fMet and its tRNA in the P site.
tRNA in the A site. |
|
|
Term
| Peptide bond formation is a _____________reaction that results in the release of water. At one time it was thought that peptidyl transferase was an enzymatic protein. However, more recently, it was discovered that peptidyl transferase is a catalytic RNA molecule. An RNA capable of catalyzing a reaction is called a_____. |
|
Definition
|
|
Term
Once the peptide bond has formed, there remains an uncharged tRNA in the_____, and a tRNA with the growing polypeptide chain in the ____.
The ribosome now moves one codon along the mRNA with the help of _____ and another GTP. An EF-G–GTP complex binds to the ribosome, hydrolysis of GTP occurs, and translocation begins. |
|
Definition
|
|
Term
Name the stop codons
True or false....There are no tRNAs that recognize the STOP codons UAA, UAG, or UGA
What recognizes the stop codons? |
|
Definition
UAG UAA UGA
true
RF (release facftors) recognize STOP codons and interact with GTP
|
|
|
Term
| A mutation resulting in a premature STOP codon is called a ___________ |
|
Definition
|
|
Term
____consists of three distinct steps to add one amino acid
Requires three elongation factors: ___ ___ ___
Requires two GTPs per cycle
Occurs many times per polypeptide
The elongation cycle is similar in prokaryotes and eukaryotes.
Fast: 15-20 amino acids added per second
Accurate: 1 mistake every ~10,000 amino acids
Termination results in the release of the polypeptide chain
Requires one of the three STOP codons: UAA, UAG, or UGA.
Requires RF1 or RF2, and RF3 in prokaryotes (eRF in eukaryotes)
Requires one GTP
|
|
Definition
elongation
EF-Tu / EF-Ts and EF-G |
|
|
Term
| Each step of protein synthesis (initiation, elongation and termination) requires |
|
Definition
|
|
Term
what does EF-G have to do with?
what does EF-Tu invovle? |
|
Definition
EF-G catalyzes the translocation of the tRNA and mRNA down the ribosome at the end of each round of polypeptide elongation.
protein factors in elongation
P-loop NTPases of the G-protein family play particularly important roles.
EF-Tu and EF-G, are small GTP-binding proteins.
EF-Tu-GTP binds and delivers an aminoacyl-tRNA to the A site on the ribosome.
|
|
|
Term
The uncharged tRNA moves from the P site into the____,
blocking the next aminoacyl–tRNA
from attaching to the A site
until translocation is complete. |
|
Definition
|
|
Term
| The tRNA in the A site, still bound to its codon, now moves into the ____. Once this tRNA is bound correctly in the P site, the uncharged tRNA is ejected from the E site and the EF-G–GDP is released from the A site. The A site is now open for the next aminoacyl–tRNA to enter allowing the elongation process to continue. |
|
Definition
|
|
