Translation - Lecture 7 Flashcards
What is Translation?
Translation is a step in protein biosynthesis wherein the genetic code carried by mRNA is decoded to produce the specific sequence of amino acids in a polypeptide
What are the 4 phases of Translation?
Activation
Initiation
Elongation
Termination
What occurs in the Activation phase of Translation?
The Correct amino acid is covalently bonded to the correct tRNA
What occurs in the Initiation phase of Translation?
Small subunit of the ribosome binds to the 5’ end of mRNA with the help of initiation factors
Ribosome moves along the mRNA until AUG start codon is found (ATP dependent)
Initator tRNA (UAC) joins with starting codon
Large subunit joins - tRNA located in the P Site
What is occurs in the Elongation Phase of Translation?
Elongation factor brings next aminoacyl-tRNA
The next aminoacyl-tRNA binds to the Ribosome
GTP hydrolysed
Elongation factor is released from tRNA - goes to pick up a new tRNA
Peptide bond formation between amino acids in the P and A sites
EF2 moves ribosomes along the mRNA by one triplet
Empty tRNA moves to E site
tRNA with growing peptide moves from A to P
“A” site free
What occurs in the Termination phase of Translation?
The A site of the ribosome faces a stop codon
Release factor binds with the stop codon
Finished protein cleaved off
What is a codon?
Three Nucleotides
What is the anticodon?
tRNA molecules
What is the codon?
mRNA
What binds the amino acids to the tRNA molecules?
Aminoacyl-tRNA Synthetase
What is required for Aminoacyl-tRNA Synthetase to form a covalent bond between the Amino Acid and tRNA?
ATP
What are the three tRNA binding sties in the Ribosome?
(From Start to finish)
A - Aminoacyl
P - Peptidyl
E - Exit
What is the start codon?
AUG
What amino acid does the Initiator tRNA carry?
UAC Anticodon carries Methionine
What is the enzyme that catalyses peptide bond formation?
Peptidyl transferase
What moves the ribosome along by one mRNA triplet?
EF2
What are the stop codons?
UAA
UAG
UGA
What is a Polysome?
Many ribosomes moving along the same piece of mRNA at the same time
What is a Missense Nutation?
Results in a change in the amino acid sequence
What is a Nonsense Mutation?
Creates new terminating codon
Changes length of protein due to premature stop translation
What is a Silent mutation?
No change of amino acid sequence due to degeneracy of genetic code
- No effect
What is a Frameshift mutation?
Addition or deletion of a single base. This changes the reading frame of translation into protein
What do proteins in the cytosol make proteins destined for?
Cytosol
Nucleus
Mitochondria
What do bound ribosomes on the RER make proteins destined for?
Plasma Membrane
ER
Golgi apparatus
Secretion
What is modification of a protein?
The addition of further functional chemical groups
What is Degradation of a protein?
Degradation is when unwanted or damaged proteins are broken down and removed
