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Ribosomal RNA (rRNA) forms the ribosome, which translates mRNA into proteins. It can be found in free-floating ribosomes or in the rough endoplasmic reticulum. rRNA is made up of a large and small subunit that work together to attract transfer RNA (tRNA) molecules carrying amino acids. The peptidyl transferase, which joins amino acids, is a ribozyme. rRNA is essential for sustaining life and is targeted by antibiotics.
Ribosomal ribonucleic acid (ribosomal RNA or rRNA) helps form the ribosome itself. Unlike messenger RNA (mRNA), it does not carry genetic information. Instead, it combines with proteins to create a structure that systematically transforms mRNA into proteins.
The central dogma of cell biology is that DNA is transcribed into RNA, which is translated into proteins. The second step of this process, translation, is performed by the ribosome. A ribosome intercepts mRNA, which then requires specific amino acids to produce the protein for which it contains information. Ribosomal RNA forms a complex with various proteins to bind amino acids together.
Ribosomes can float freely in the cell cytoplasm or can be bound in a membrane called the endoplasmic reticulum (ER). ER that contains ribosomes is called rough ER. The proteins produced in the crude ER are transported through the ER to specific destinations. Ribosomes can also appear in different sizes. Larger ribosomes simply contain repeating copies of the same basic ribosomal RNA.
Ribosomal RNA appears as two separate parts working together. They are the large subunit (LSU) and the small subunit (SSU). The LSU and SSU move smoothly in tandem along the mRNA strand they are translating. LSU attracts transfer RNA (tRNA) molecules that carry the necessary amino acids.
The part of the ribosome at the meeting point of the two subunits that does the job of joining amino acids is called peptidyl transferase. It is a catalyst: it facilitates a chemical reaction by creating an environment in which the reaction can take place easily. As such, it is called a ribozyme and is one of the few organic catalysts that is not a protein.
Living organisms contain several hundred copies of the genes required for the two ribosomal RNA molecules. This abundance and redundancy reflect the crucial role this RNA plays in sustaining the process of life. There is no known organism on Earth that would be able to function without rRNA.
Ribosomal RNA is as basic and widespread among bacteria as it is in the animal kingdom. As a result, many antibiotics target ribosomal RNA in bacteria. This rRNA is unique enough that it can be targeted without killing the infected organism, but also similar enough between bacteria that single antibiotics can kill many different strains. Many of these antibiotics are naturally occurring chemicals: products of the benefits bacteria can gain by independently killing each other!
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