Ribosome
Cell Biology · Molecular Biology
Say it: RY-buh-sohm
A ribosome is a molecular machine of RNA and protein that reads messenger RNA and joins amino acids in the order it specifies to build a protein.
Also: ribosomes
Definition
What is a ribosome?
A ribosome is the structure that carries out translation, the step of gene expression in which a protein is assembled. It is made of ribosomal RNA and proteins arranged in two subunits, one large and one small, which come together around a strand of messenger RNA (mRNA). Ribosomes are found in every cell, and also inside mitochondria and chloroplasts.
As the ribosome moves along the mRNA, it reads the code three bases, or one codon, at a time. Transfer RNA molecules bring in the matching amino acids, and the ribosome links each new amino acid to the growing chain with a peptide bond. When it reaches a stop codon, it releases the finished chain and its two subunits come apart, ready to be used again.
In eukaryotes, ribosome subunits are assembled in the nucleolus. Finished ribosomes either float free in the cytoplasm, making proteins for use inside the cell, or attach to the rough endoplasmic reticulum, making proteins for membranes or for export. Bacterial ribosomes (70S) are smaller and built differently from those in the human cytoplasm (80S), a difference that many antibiotics exploit.
Word parts
Where does the word “ribosome” come from?
- ribo-
- from ribose, the sugar in RNAribose, a coined chemical name
- -some
- bodyGreek soma
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Terms that go with it
- TranslationTranslation is the process in which a ribosome reads the codons of a messenger RNA and links amino acids in that order to build a protein.
- Messenger RNAMessenger RNA is the RNA copy of a gene that carries protein-building instructions from DNA to the ribosomes, where it is read in three-base codons.
- Transfer RNATransfer RNA is a short adaptor RNA that brings a specific amino acid to the ribosome and pairs with the matching mRNA codon through its anticodon.
- CodonA codon is a sequence of three nucleotides in DNA or messenger RNA that stands for one amino acid or tells the ribosome to stop.
- ProteinA protein is a large molecule made of one or more chains of amino acids, folded into a specific shape that determines its job in the body.
- Endoplasmic reticulumThe endoplasmic reticulum is a network of membrane sacs and tubes in eukaryotic cells that makes and processes proteins and lipids.
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Written for biofideX in plain words, after checking these references:
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