chapter 14 Flashcards
the biological polymerization of amino acids into polypeptide chains
- requires mRNA, tRNA, amino acids, and ribosomes
Translation
serve as adaptor molecules to adapt the triplet codons in mRNA to the correct amino acid
tRNA
base adenine, has a NH2
adenosine
deaminated adenosine; base hypoxanthine
Inosine
(rare bases in tRNA)
A tRNA has an _ that base-pairs with the codon in the mRNA
anticodon
- s catalyze attachment of amino acid to tRNA
- charges (activates) tRNAs with the appropriate amino acid
Aminoacyl-tRNA synthetases
where translation occurs
ribosome
prokaryotic cells have _ type of ribosome located in the ___
1; cytoplasm
eukaryotic cells have __ types of ribosom:
located in
2 ; cytoplasm & organelles
- consist of ribosomal proteins and ribosomal RNAs
- have large and small subunits
- rRNAs provide for important catalytic functions associated with translation
ribosomes
ribosome: small subunit binds to
mRNA
3 distinct binding areas
E,P, and A sites
large subunit has _
peptidyl transferase activity
- the small and large ribosomal subunits
- GTP
- charged initiator tRNA, Mg2+
- initiation factors
translation initiation requires
In bacteria, the AUG start codon is preceded by a _), which base-pairs with a region of the 16S rRNA of the _S small subunit
Shine-Dalgarno sequence (AGGAGG); 30
1) small ribosomal subunit binds first
2) fMet tRNA positioned in P site
3) then the large subunit binds
Three sequential steps in initiation phase:
in eukaryotic initiation tRNA is designated with _;
- it carries methionine rather than a formylmethionine
- 40s subunit
tRNA met
consensus sequence for optimal start codon recognition
- aka Kozak’s consensus
A/G at -3 and AUG G at 1,2,3, 4
Small ribosomal subunit binds to 5’ cap, then scans the mRNA for the first AUG codon
initiation phase in eukaryotes
Initiation factors bind to the _ cap in mRNA & to the _
5’ ; polyA tail
Once right AUG found, the _ subunit joins
60S
Addition of amino acids to C-terminus of polypeptide
Elongation phase
elongation requires both ribosomal subunits assembled with the mRNA to form the _site and _ site
P (peptidyl) site and A (aminoacyl) site
Charged tRNAs ushered into A site by _
elongation factors
