Question

What prevents the two subunit of ribosome to bind together befor tehy are attached to mrna

Answer 1

Introduction

Translation requires some specialized equipment. Just as you wouldn't go to play tennis without your racket and ball, so a cell couldn't translate an mRNA into a protein without two pieces of molecular gear: ribosomes and tRNAs.

Ribosomes provide a structure in which translation can take place. They also catalyze the reaction that links amino acids to make a new protein.

tRNAs (transfer RNAs) carry amino acids to the ribosome. They act as "bridges," matching a codon in an mRNA with the amino acid it codes for.

Here, we’ll take a closer look at ribosomes and tRNAs. If you're not yet familiar with RNA (which stands for ribonucleic acid), I highly recommend checking out the nucleic acids section first so you can get the most out of this article!Structure of the ribosome

A ribosome is made up of two basic pieces: a large and a small subunit. During translation, the two subunits come together around a mRNA molecule, forming a complete ribosome. The ribosome moves forward on the mRNA, codon by codon, as it is read and translated into a polypeptide (protein chain). Then, once translation is finished, the two pieces come apart again and can be reused.

Overall, the ribosome is about one-third protein and two-thirds ribosomal RNA (rRNA). The rRNAs seem to be responsible for most of the structure and function of the ribosome, while the proteins help the rRNAs change shape as they catalyze chemical reactions^1

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Below, you can see a 3D model of the ribosome. Proteins are colored in blue, while strands of rRNA are colored in tan and orange. The green spot marks the active site, which catalyzes the reaction that links amino acids to make a protein. It surprised me to see that the ribosome is wrinkly, kind of like the surface of a brain!