Question

Describe the structure of a ribosome and its three sites. Explain how it interacts with an mRNA and tRNAs to build a protein.

Answer 1

Structure of ribosome - They are made up of RNA and protein. They read RNA and synthesizes protein. Ribosomes are composed of two subunits, small and large subunits. At large subunit the amino acids get added to the growing protein chain. At small subunits, the mRNA binds and decodes. Three binding sites located on the ribosome, for tRNA and one binding site for mRNA. The three receptor sites are P, A and E. The A site, acceptor site binds to the aminoacyl tRNA, which holds the new amino acid to add to the polypeptide chain. The P site, peptidyl site, binds to the tRNa holding the growing polypeptide chain of amino acids. The E site, exit site, serves as threshold, the final transitory step binds a free tRNA.

Each tRNA has sequence of three nucleotides located in a loop at one end of the molecule that can basepair with an mRNA codon. This is called the tRNA's anticodon. Synthesizing a protein from an mRNA sequence occurs on ribosomes. Amino acids are brought to the ribosome by trnas.