Translation

What role does the ribosome play in assembling proteins?

The sequence of nucleotide bases in an mRNA molecule is a set of instructions that gives the order in which amino acids should be joined to produce a polypeptide. Once the polypeptide is complete, it then folds into its final shape or joins with other polypeptides to become a functional protein.

If you've ever tried to assemble a complex toy, you know that instructions alone don't do the job. You need to read them and then put the parts together. In the cell, a tiny factory—the ribosome—carries out both these tasks. Ribosomes use the sequence of codons in mRNA to assemble amino acids into polypeptide chains. The decoding of an mRNA message into a protein is a process known as translation.

Steps in Translation Transcription isn't part of the translation process, but it is critical to it. Transcribed mRNA directs that process. In a eukaryotic cell, transcription goes on in the cell's nucleus; translation is carried out by ribosomes after the transcribed mRNA enters the cell's cytoplasm. Refer to Figure 13–7 as you read about translation.

A Translation begins when a ribosome attaches to an mRNA molecule in the cytoplasm. As each codon passes through the ribosome, tRNAs bring the proper amino acids into the ribosome. One at a time, the ribosome then attaches these amino acids to the growing chain.

VISUAL SUMMARY

TRANSLATION

FIGURE 13–7 During translation, or protein synthesis, the cell uses information from messenger RNA to produce proteins.

dd

Table of Contents