Unit 3 - Translation (Nucleic Acid to Polypeptide) Flashcards
Translation from RNA to proteins
is the assembly of aa into a polypeptide using info encode in the mRNA
initation simple
a ribosome binds to mRNA
elongation simple
tRNA delivers right aa to the ribosome for + to the growing pp chain
Termination simple
transcription ceases, and the polypeptide is released
transfer RNA to tRNA
small RNAs - abt 70 to 90 nucleotides long making a cloverleaf pattern
function of transfer RNA - tRNA
delivers correct aa to ribosomes (recognition between codon and anticodon is complementarity)
if anticodon is 3’-UCA-5’ what is the complimentary codon
5’-AGU-3’
Transfer RNA
-amminoacyl-RNA
-enzymes adds AAs to each tRNA
-attached via ESTER BONS
-amino acid to a tRNA is called aminoacylation
Ribosomes
- free-floating in cytoplasm or temporary associated w the rough ER
- Eukaryotes recognize the 5’cap of mRNA transcript
Eukaryotic ribosome
-made pf two diff sized parts called LARGE (50s) and SMALL (30s) ribosomal subunits
subunits made up of
a combination of ribosomal RNA (rRNA) and ribosomal proteins
initiation step 1 in debth
AUG start
- assembly of initiation complex
- Met-tRNA forms a complex w the small ribosomal subunit
Initiation step 2 in debth
- complex binds mRNA at 5’ cap
- moves along the mRNA (process = scanning) until it finds the first AUG codon
Elongation
ribosome moves along the mRNA in the 5’ to 3’ direction
- condons read = amico acids
elongation = three sites for tRNA
a (aminoacyl)
p (pepdityl)
e (exit)
aminoacyl site
where incoming aminoacyl-tRNA anticodon binds to mRNA codon
pepdityl site
tRNA with growing chain is bound
exit site
exiting tRNA leaves the ribosome
Elongation step 1 in depth
an aminoacyl-tRNA binds the A site
Elongation step 2 in depth
peptidyl transferase cleaves the aa from the P site tRNA and bonds it to the aa on the A site tRNA
Elongation step 3 in depth
the ribosome moves codon
- tRNA with the growing polypeptide is now in P site
- empyt tRNA is now E site
Elongation step 4 in depth
Empty tRNA in E site is now released and the cycle repeats
Reading Frame
positioning of ribosome on the mRNA is important and is where mRNA is read and depending on bp from which the ribosome starts translating
Termination
tRNA that exit from the P site are recycled by adding more AAs to them
- chain grows until a stop Condon arrives in A site
release factor
protein binds in A site
+ protein dismantles the ribosome mRNA complex and the polypeptide chain is released along w the tRNA
