What is a ribosome?
Ribosome is the organelle concerned with the synthesis of protiens
Protein molecule is made up of large number of amino acids arranged in specific sequence. The amino acids are joined together by peptide linkage (NH-CO) formed by reaction of NH2OH group of one amino acid and -COOH group of adjoining amino acid, with the removal of H2O molecule.
The sequence of amino acids in protein molecule is controlled by the genetic code, the sequence of nucleotides in DNA molecule that is located in the nucleus.
DNA does not move out of the nucleus, but sends the message to ribosome through mRNA that gets attached to smaller sub-unit of ribosome.
Each amino acid has specific sequence of codons of mRNA. Each amino acid has specific tRNA having codon sequence complementary to codon sequence of its specific mRNA.
During protein synthesis, all amino acids are attached to their specific tRNAs and are wandering in cytoplasm. Ribosome moves over mRNA and various tRNAs reach the acceptor site of ribosome as per the sequence of codons on mRNA. In this way, various codons of mRNA in specific sequence reach the acceptor site and various amino acids are reaching the acceptor site as per the sequence of mRNA codons.
A protein molecule is thus synthesized at the ribosome and is released when the termination codon reaches the acceptor site, because there is no amino acid tRNA having anticodon for that codon sequence.