Sometimes biology can seem confusing, usually due to the fact that there is a ton of information to learn on every function within a living thing. But this can be overcome by learning bits of information and building it back up into the larger picture of life and what it means. Ribosomes are part two of our journey through the eukaryotic cell and its many organelles. Be sure to check out the other entries as the go up for a basic overview of the cell and what it does.
A ribosome does not have a phospholipid membrane as do most other organelles, so it is known in certain instances as a “non-membranous organelle”. Ribosomes are first of all produced within the nucleolus and are made up of a type of RNA called ribosomal RNA and different kinds of proteins creating two different sized subunits (strands of ribosomal RNA and ribosomal proteins). Their job within the cell is to take nucleic acids delivered by transfer RNA and produce proteins in a process called translation. Messenger RNA gives the instructions on what type of protein is to be made for the cell. Once ribosomes are assembled they leave the nucleus through nuclear pores.
Ribosomes can be found within eukaryotic cells in two places
1. Cytoplasm, occurring as either free ribosomes or attached to the endoplasmic reticulum.
2. Inside mitochondria and chloroplasts.
Free ribosomes move about the cytosol (semi fluid medium of the cytoplasm) and create proteins for the cell that are usually utilized within the cytosol. The ribosomes that are attached to the endoplasmic recticulum will produce proteins that are to be used within the cell membrane (surface receptors), lysosomes, or outside of the cell when exocytosis (material in vesicles is expelled from the cell) occurs. The product of the ‘bound’ ribosomes (polypeptide/protein) is sent into the endoplasmic recticulum before it is processed and distributed by the golgi apparatus. Cells that require more protein synthesis contain more ribosomes and most human cells contain millions of them. They also occur in prokaryotic cells without being bound to any organelle obviously and are smaller than the ones found in eukaryotic plant and animal cells.
Ribosomes are without a doubt more complex than what this article provides but this was a simple primer on what they do and what exactly their function is. I didn’t include a step by step breakdown of the process of protein synthesis or give any names of the proteins involved in the ribosomes make up. If you wish to learn more read a damn book!
Life: The Science of Biology 7th edition by Sadava