Translation

Question 1

why are codon 3 letters long

Answer 1

there are 20 amino acids which need to be uniquly coded for, 4^3 = 64, which is the smallest demonination giving a minimum of 20 codons. this gives 61 amino acid coding codons and 3 stop codons

Question 2

what is the role of tRNA in translation
note on shape.

Answer 2

Amino acids cannot directly interact with mRNA. tRNA has an anticodon which can interact with mRNA and an amino acid attachment site to bind to an amino acid.

the 3d shape is also very importnat as it fits into the sections of ribosomes

Question 3

how do tRNA become chanrged

Answer 3

each amino acid has a different enzyme which binds a tRNA to that amino acid. this makes a charged tRNA ready for transcription

Question 4

describe ribosomal structure

Answer 4

Ribosomes are made from rRNA and the small and large ribosomal sub unit. they have the A, P and E sites. they have an exit tunnel for the forming polyamino acid to be released from

Question 5

What are the three stages of translation

Answer 5

initiation
elongation
termination

Question 6

describe the steps occuring at of initation translation

Answer 6

tRNA binds to a small ribosomal sub unit which will then locate the active G site of an mRNA.
They will then move down the 5’->3’ direction of mRNA until they find the start codon
The large ribosomal subunit will then bind onto the small ribosomal sub unit with the inital tRNA in the P site. this forms the initation complex

Question 6

describe the steps occuring at elongation of translation

Answer 6

A tRNA with an anticodon which is complementary to the next codon will bind to the A site.
then at the same time the ribosome will shift one cdon in the 5’->3’ direction while the poly amino acid bound to the tRNA in the P location is bonded to the new amino acid in the A location
due to the ribosomal movement the A-> p and P-> E location
the tRNA whihc is no longer charged in the E site exits the ribosome
the next tRNA binds to the A site

Question 6

describe the steps occuring termination at of translation

Answer 6

when a stop codon is the next codon in the mRNA a release factor binds to this section of mRNA in the A site. this then hydrolises the bond between the P site trna and the polyamino acid releasing this into the cytosol to undergo compleation. the small and large ribosomal sub units then dissociate

Question 7

after a translation is the protein compleated

Answer 7

no, often the first amino acid is lost aswell as other processes to make a functional protein