Translation Flashcards
Initiation/ start codon
AUG
Anticodon of the start/ initiation codon
UAC
3 stop/ terminating codons
UGA
UAG
UAA
is the process of decoding the mRNA into a polypeptide chain
Translation
read mRNA three bases or 1 codon at a time and construct the proteins
Ribosomes
Ribosomes are composed of rRNA (____) and proteins (____)
rRNA 40%
proteins 60%
three sites for tRNA attachment —
E, P and A
holds the aatRNA carrying the next amino acid to be added
A site
aminoacyl-tRNA site
holds the tRNA molecule carrying the growing polypeptide chain
P site
peptidyl-tRNA site
where tRNA molecules leave the ribosome
E site
Exit site
Single stranded molecule with attachment site at one end for an amino acid
Opposite end has three nucleotide bases called the anticodon
Transfer RNA
tRNA
is an enzyme that attaches the appropriate amino acid onto its tRNA
AMINOACYL-TRNA SYNTHETASE
catalyzes the esterification of a specific amino acid to one of its compatible tRNAs to form an aminoacyl-tRNA
AMINOACYL-TRNA SYNTHETASE
Once the tRNA is______, a ribosome can transfer the amino acid from the tRNA onto a growing peptide, according to the genetic code
charged
tRNA with amino acid attached to it
Charged/ loaded tRNA
THREE PHASES OF TRANSLATION
Initiation
Elongation
Termination
starts with mRNA binds to a small ribosomal subunit, positioning the initiating codon AUG in the P site
An activated tRNA with a complementary anticodon to the codon AUG attaches to it through base pairing
The resulting complex then interacts with a large ribosomal subunit to complete the formation of an initiation complex
Initiation
The mRNA moves a codon at a time relative to the ribosome
A tRNA pairs with each codon, adding an amino acid to the growing polypeptide
A _______ causes the mRNA-ribosome complex to fall apart
Elongation
STOP codon
requires energy
Ribosome moves:
tRNA from P site to E site: leaves ribosome
tRNA from A site to P site: polypeptide returns to P site, ready for next polymerization
A site is now empty
next aatRNA can bind
Translocation
At stop codon a protein called ________ binds to A site (no tRNA for stop codon, thus no aatRNA)
Release factor:
adds of_____ molecule instead of amino acid to polypeptide
polypeptide hydrolyzed from tRNA in P site and released
Translation complex disassembles
Termination
release factor - adds water
The end products of protein synthesis is a ______ structure of a protein
A sequence of amino acid bonded together by______ bonds
primary structure of a protein
peptide
Met residue is removed by hydrolysis
second hydrolysis reaction releases the polypeptide chain from its tRNA carrier
Some covalent modification of a protein can occur, such as the formation of disulfide bridges between cysteine residues
Completion of the folding of polypeptides into their active conformations occurs
POST-TRANSLATION PROCESSING
