A bound ribosome is an organelle involved in the synthesis of cellular protein that is attached to the endoplasmic reticulum (ER) inside a cell. The endoplasmic reticulum is called the rough ER when there are ribosomes embedded within it. Bound ribosomes are identical in structure to ribosomes that are free-floating in the cytosol of the cell; they differ only in the specific action of the protein that they synthesize. For example, ribosomes that are membrane-bound are more involved in creating proteins that are exported through exocytosis to other cells and tissues throughout the body. Proteins produced by this classification of ribosome can be directly inserted into the rough ER, where they can be transported for extracellular action without going through multiple steps.
Membrane-bound proteins only make up a small portion of the total number of ribosomes within the cell, but they are essential for complicated protein synthesis and eventual transport, which involves the incorporation of large amounts of amino acids to be transported outside the cell. Fetuses and newborn babies have significantly more bound ribosomes than older individuals, and this can help explain why the young assimilate proteins at a faster rate, accounting for periods of rapid growth and cell differentiation. All ribosomes, and in particular, bound ribosomes, initiate the transcription process that lets the body carry out the instructions it receives from the deoxy-ribonucleic acid (DNA). The scientist George Palade was the first to discover the differing functions and patterns of membrane-bound ribosomes in DNA transcription, specifically.
An individual-bound ribosome is a combination of two units: the smaller, which attaches to the messenger ribonucleic acid (mRNA), and the larger, which attaches to the transfer ribonucleic acid (tRNA). The mRNA is made from a set of specific codons that transfer information to the protein transcription system of the associated side of the membrane-bound ribosome. Then, the larger tRNA end of the ribosome reads a set of complementary codons, which initiates the transfer of translated information. The ribosome works its way through the RNA, reading each set of codons as it moves. The work of the bound ribosome can be thought of as an interpreter of an individual’s blueprint that is present upon conception.
The protein synthesis process begins at the codon, AUG, which is near the end of the mRNA. The bound ribosome alternates, creating proteins from available amino acids. Protein synthesis ends when a set of complete proteins are made. After this event, many bound ribosomes detach from the endoplasmic reticulum and become free ribosomes.