Translation (RNA - Protein) Flashcards
U2L4b
What are the three phases of RNA translation?
Initiation
Elongation
Termination
What happens in the Initiation phase?
In the initiation phase, the ribosomes recognize the 5’ cap on the mRNA strand, causing ribosomal subunits to ‘sandwich’ on to eachother with the strand in the between, forming a ribosomal complex.
Ribosomes then move along the mRNA strand in the 5’-3’ direction until it reaches the first codon.
What’s a codon?
A codon is a section which is composed of three nucleotides.
Codons are what code for a specific amino acid.
What does tRNA do?
tRNA carries individual amino acids to the ribosomal subunit, which eventually causes a polypeptide chain to form (more on that later).
one arm on the tRNA has an anticodon (nucleotides that are complimentary to the codons on the mRNA).
What happens in elongation?
in Elongation, the first codon is recognized and read as a ‘start’ sequence. This causes tRNA to enter the ‘P’ section of the unit. The tRNA carried a ‘MET’ amino acid which is always found on the beginning of any polypeptide chain.
What are the three sites found in the Ribosomal complex?
Exit Site (E)
Peptide Site (P)
Acceptor Site (A)
What happens in the termination phase?
The Ribosomal complex reads one of three codons: UAG, UGA or UGG. This causes a protein called a release factor to enter the activator site. The activator site looks similar to tRNA but contains NO amino acids. This essentially causes the polypeptide chain to be released to the surrounding region and causes the ribosomal complex to disassociate while it waits for the next strand to work on.
What happens after the polypeptide chain is formed?
Well as we learned last unit, it could bind with other polypeptide chains and fold over itself (secondary, tertiary and quaternary structures) and make proteins like hemoglobin.
