8.5 Translation, polypeptide synthesis Flashcards
What is a triplet code of DNA transcribed into on mRNA
A codon
How many different types of tRNA is there
What is on tRNA that is important for translation
Around 60
They have anticodons
Once mRNA passes out of a nuclear pore, what is the process of translation
Use an example of codons, that do not need to be learned
. Ribosome in cytoplasm becomes attached to starting codon (AUG) at one end of mRNA molecule.
. The tRNA molecule that has a complimentary anticodon sequence UAC moves to the ribosome and pairs with the codon on mRNA.
. This tRNA molecule carries an amino acid with it (methionine)
. A tRNA molecule with the complimentary codon UGC pairs with the next codon on the mRNA (ACG) .
. This tRNA molecule carries another amino acid (threonine)
. The ribosome moves along the mRNA, bringing together two tRNA molecules at any one time, each pairing up with the corresponding two codons on mRNA
. The amino acids on the tRNA are joined by a peptide bond using an enzyme and ATP which is hydrolysed to provide the energy for it.
-The ribosome moves to the third codon (GAU) in the mRNA sequence, and the tRNA that has the anticodon for it has amino acid aspartic acid.
This aspartic acid will form a peptide bond with the threonine from before.
As these bind, the first tRNA is released from its amino acid methionine and is free to collect another methionine from the amino acid pool in the cell
. Many identical polypeptides can be assembled simultaneously as up to 50 ribosomes can pass immediately behind the first
. This protein synthesis occurs until it reaches a stop codon so the mRNA, tRNA and ribosomes separate and amino acid polypeptide chain is complete.
When does translation stop
This protein synthesis occurs until it reaches a stop codon on the mRNA so the mRNA, tRNA and ribosomes separate and amino acid polypeptide chain is complete.
What effect does the DNA sequence of triplets on mRNA, tRNA and overall the polypeptides made
The DNA triplet is responsible for the complimentary codon on mRNA
The sequence of codons on mRNA determine what order the tRNA molecules line up to connect their amino acids
The order of amino acids impacts the polypeptide chain, so what proteins are made
What happens to the polypeptide chain produced , how is it assembled into a protein
. It is coiled or folded into secondary structure
. Then this secondary structure is folded more, producing tertiary structure
. Different polypeptide chains along with prosthetic groups are linked to form quaternary structure
