Explain the process of translation of proteins in a ribosome.

Translation is the process by which mRNA strands are converted into polypeptides that can be used within the cell or released from the cell in order to carry out specific functions. There are four stages to translation; initiation, elongation, translocation and elimination.Initiation is the process by which the ribosome complex is assembled around the mRNA strand. The small subunit binds first to the 5' end and moves along the mRNA until the start codon (AUG) is found. The tRNA with the complementary anticodon for AUG then binds to the mRNA using the principle of complementary base-pairing. Then large subunit of the ribosome then aligns itself with the tRNA molecule in the P site of the ribosome, forming the ribosome complex.After initiation, elongation occurs. This process begins the repeated cycle that is responsible for ensuring the whole mRNA chain is read and translated. The second tRNA is bound into the A site and the amino acid attached to the original tRNA is covalently bonded to the amino acid in the A site by a peptide bond, through a condensation reaction. The original tRNA is now deacylated and the A site tRNA carries the polypeptide chain.Translocation is the process by which the ribosome complex moves along the mRNA chain to translate the next portion of code, it moves one codon in the 5'-3' direction. The tRNA in the P site moves to the E site and is removed from the complex and the tRNA with the polypeptide chain is moved to the P site. A new tRNA that is complementary to the codon now in the A site binds and the processes of elongation and translocation repeat, until a stop codon is reached.When a stop codon is reached, elimination is triggered. The stop codons do not code for a tRNA molecule, but instead retrieve factors that disassemble the ribosome complex. The polypeptide is released and the ribosome is removed from the mRNA, this mRNA can then be used to code for another, identical, polypeptide, or it can be destroyed by the enzymes within the cell.

Answered by Sarah C. Biology tutor


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