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rRNA Function, Location Production, & Synthesis

Deedhiti Patel, Shannon Compton
  • Author
    Deedhiti Patel

    My name is Dee Patel and I am a current dental student in my third year! I graduated from the University of Massachusetts in 2018 with my degree in Biology. There, I also worked as a biology tutor and teachers assistant for freshman biology.

  • Instructor
    Shannon Compton

    Shannon teaches Microbiology and has a Master's and a PhD in Biomedical Science. She also researches cancer and neurodegenerative diseases.

Define ribosomal RNA. Learn rRNA types, locations, and roles in protein synthesis. Understand inference of rRNA gene sequences in taxonomy and medical studies. Updated: 12/04/2021

What is Ribosomal RNA (rRNA)?

All proteins made within the body go through the process of DNA transcription and translation. DNA transcription is the process of converting DNA into RNA. During the process of translation, the transcribed RNA is used as a genetic blueprint to convert the information into proteins, which are necessary for the functions of all cells within the body.

Within this process of DNA transcription and translation, when DNA is converted into RNA, there are three different RNAs that are crucial to the process of protein synthesis. The three different types of RNA include messenger RNA (mRNA), transfer RNA (tRNA), and ribosomal RNA (rRNA).

In eukaryotic cells, when the DNA is transcribed into MRA, that very first transcription produces pre-mRNA. This first transcription is known as pre-mRNA because, in order for it to be translated into a blueprint that can be used for protein synthesis, it must undergo maturation. When the DNA is transcribed into RNA, the pre-mRNA contains non-coding regions, known as introns, which must be spliced out from the coding strand. Once the introns are spliced out from the pre-mRNA, the pre-mRNA undergoes maturation, and the coding strands (exons) are joined together. Once the coding regions are joined together, a 5 prime cap and 3 prime poly-A tail are added onto the RNA strand, which then makes the strand mature mRNA. This mature mRNA is now ready to move on to the next step of protein synthesis.

mRNA from the previous step is now ready to be translated into proteins. This synthesis of proteins is done through tRNAs. tRNAs are molecules that translate the mRNA into proteins.

The structure of tRNA resembles that of a 3-leaf clover. The 3 leaves are hairpin structures, and one of the hairpin structures is known as the anti-codon region. This anticodon region is where the mRNA is read and the corresponding amino acid is added amino acid chain. This process continues until the mRNA strand has been translated into a protein.

rRNA is a non-coding RNA that helps to form ribosomes, which are the protein-synthesizing organelle of the cell. rRNA when encoded are either small or large. These small and large rRNA's combine with ribosomal proteins and once assembled in the proper location, serve as ribosomal subunits for protein synthesis.

rRNA can be measured using Svedberg units, and this unit is composed of the particles' mass, density, and shape. The value of this unit is labeled 'S' and is based on how quickly it will settle to the bottom of a solution. For example, a bigger particle will have a higher S value because it will settle faster at the bottom of a given solution.

Eukaryotic rRNA = 60S and 40S = when combined is 80S = created in the nucleolus

Prokaryotic rRNA = 50S and 30S = when combined is 70S = created in the cytoplasm

What Is rRNA?

To begin, ribonucleic acids (RNA) are a group of large molecules that have many different roles. They are especially important in the coding, decoding, regulation, and expression of our genes. As the name implies, ribosomal RNA (rRNA) is part of the ribosome. A ribosome is the protein builder of the cell. The rest of a ribosome is made up of proteins. In addition, there are two rRNA in each ribosome, one in the large subunit and one in the small subunit.

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This picture depicts the small and large subunits coming together

rRNA Function in Protein Synthesis

Protein synthesis is dependent on organelles known as ribosomes. Ribosomes are the location in which the RNA is translated into proteins. Each ribosome is composed of a large subunit and small subunit, as well as ribosomal proteins. The ribosome acts as a binding site for the codons of mRNA and tRNA. mRNA is what provides the blueprint of the protein strand that is to be synthesized. Once the pre-mRNA undergoes maturation, the mRNA is then used as a blueprint by tRNA to assemble the proper amino acids for the protein chain. This process takes place within rRNA. And in this way, rRNA provides the location for mRNA and tRNA to come together.

Function

Translation is the name of the process our cells use to make proteins. Ribosomes are the organelles that can take a copy of our genetic material and translate it into a protein. The original genetic material is DNA, and it is stored in the cell's nucleus. When a specific protein is needed, our cells make a copy of the DNA. This copy is also RNA, but it is called messenger RNA, or mRNA. Thus, ribosomes translate mRNA into protein.

To make a protein, ribosomes link together amino acids. The mRNA has the specific order in which the amino acids must be joined, and each protein has a different order of amino acids. The small subunit of rRNA can read the order of amino acids. Linking amino acids together is the function of the rRNA in the large subunit of the ribosome.

Sequence

rRNA Subnits
table of components of rRNA subunits

The sequence of rRNA is highly complex and derived from multiple genes. The table summarizes the components of the large and small subunit rRNA. Sedimentation rate (S) of the subunit is affected by the size of each subunit. As you can see, the large subunit of rRNA is made of two smaller pieces, while the small subunit is only one piece. The structure of the small subunit of eukaryotic rRNA has been discovered.

Synthesis

All RNA molecules are created by transcription, or making a copy of DNA. The protein that makes a copy of DNA is RNA polymerase. This protein is an enzyme that can read DNA and make an RNA copy. Transcription starts when the RNA polymerase enzyme binds DNA at a specific location called a promoter. Promoters are found 'upstream' of a gene. RNA polymerase reads the DNA in only one direction and continues reading and creating RNA until it reaches the end of the gene. The end of the gene has a special region called a stop codon. This region literally signals the RNA polymerase enzyme to stop copying the DNA.

Importance

Ribosomal RNA characteristics are important in medicine. Both prokaryotes (single-celled organisms, like bacteria) and eukaryotes (organisms whose cells have a nucleus and organelles, like the cells in our bodies) have ribosomes with rRNA. Prokaryotes and eukaryotes differ in the size and sequence of the rRNA in each subunit. Modern medicine exploits this difference using antibiotics. Therefore, rRNA is the target of several antibiotics, including chloramphenicol, erythromycin, and streptomycin.

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Video Transcript

What Is rRNA?

To begin, ribonucleic acids (RNA) are a group of large molecules that have many different roles. They are especially important in the coding, decoding, regulation, and expression of our genes. As the name implies, ribosomal RNA (rRNA) is part of the ribosome. A ribosome is the protein builder of the cell. The rest of a ribosome is made up of proteins. In addition, there are two rRNA in each ribosome, one in the large subunit and one in the small subunit.

Function

Translation is the name of the process our cells use to make proteins. Ribosomes are the organelles that can take a copy of our genetic material and translate it into a protein. The original genetic material is DNA, and it is stored in the cell's nucleus. When a specific protein is needed, our cells make a copy of the DNA. This copy is also RNA, but it is called messenger RNA, or mRNA. Thus, ribosomes translate mRNA into protein.

To make a protein, ribosomes link together amino acids. The mRNA has the specific order in which the amino acids must be joined, and each protein has a different order of amino acids. The small subunit of rRNA can read the order of amino acids. Linking amino acids together is the function of the rRNA in the large subunit of the ribosome.

Sequence

rRNA Subnits
table of components of rRNA subunits

The sequence of rRNA is highly complex and derived from multiple genes. The table summarizes the components of the large and small subunit rRNA. Sedimentation rate (S) of the subunit is affected by the size of each subunit. As you can see, the large subunit of rRNA is made of two smaller pieces, while the small subunit is only one piece. The structure of the small subunit of eukaryotic rRNA has been discovered.

Synthesis

All RNA molecules are created by transcription, or making a copy of DNA. The protein that makes a copy of DNA is RNA polymerase. This protein is an enzyme that can read DNA and make an RNA copy. Transcription starts when the RNA polymerase enzyme binds DNA at a specific location called a promoter. Promoters are found 'upstream' of a gene. RNA polymerase reads the DNA in only one direction and continues reading and creating RNA until it reaches the end of the gene. The end of the gene has a special region called a stop codon. This region literally signals the RNA polymerase enzyme to stop copying the DNA.

Importance

Ribosomal RNA characteristics are important in medicine. Both prokaryotes (single-celled organisms, like bacteria) and eukaryotes (organisms whose cells have a nucleus and organelles, like the cells in our bodies) have ribosomes with rRNA. Prokaryotes and eukaryotes differ in the size and sequence of the rRNA in each subunit. Modern medicine exploits this difference using antibiotics. Therefore, rRNA is the target of several antibiotics, including chloramphenicol, erythromycin, and streptomycin.

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Frequently Asked Questions

What is the function of rRNA?

The function of rRNA is to serve as a location for protein synthesis. rRNA is the location in which mRNA and tRNA are able to come together to synthesize proteins.

Where is rRNA?

rRNA in eukaryotic cells is synthesized in the nucleolus and found in the cytoplasm and in prokaryotic cells is synthesized and found in the cytoplasm.

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