Ribosome is a cell organelle present in the cytoplasm of all living cells. It is a site of protein synthesis in all type of cells. It is made up of two sub-units namely, small sub-unit and large sub-unit.
Both the sub-units are formed by rRNA (ribosomal RNA) and associated proteins. rRNA is ribozyme, that is, it is a ribonucleic acid with catalytic ability. The protein component helps in providing the structure to the ribosome.
Ribosomes are membrane-free granules made up of protein-associated RNA molecules, present in all cell types and visible only through the electron microscope. They are formed by two subunits of different sizes and densities, being called major and minor.
Ribosomes are responsible for the synthesis of proteins by joining their amino acids. This synthesis is controlled by mRNA (messenger RNA) formed in gene transcription under DNA command. MRNA, associated with a group of ribosomes called polyribosomes, guides the sequence of amino acids that will form proteins. These amino acids are brought by the tRNA (carrier RNA) and are nested according to the sequence determined by the mRNA. As polyribosomes traverse the mRNA strand, proteins are synthesized.
Vestigial structures are parts of an animal's body that serve no function, but did in earlier evolutionary stages. Two examples of this are the human appendix and the snake pelvic bone.
