Difference Between rRNA and Ribosomes

The key difference between rRNA and ribosomes is that rRNA is the RNA component of the ribosomes, which is a nucleic acid while ribosome is an organelle that carries out protein synthesis.

rRNA and ribosomes are two different entities that work together in cellular functions, especially in the translation process of living organisms. One is a macromolecule while the other is a small organelle which is extremely important. These two entities possess different characteristics, yet they may not be very familiar for many of you. Therefore, it would be of great importance to present their characteristics and discuss the difference between rRNA and ribosomes as well.

CONTENTS

1. Overview and Key Difference
2. What is rRNA 
3. What are Ribosomes
4. Similarities Between rRNA and Ribosomes
5. Side by Side Comparison – rRNA vs Ribosomes in Tabular Form
6. Summary

What is rRNA?

rRNA is the standard, shortened form for the ribosomal RNA. It is a nucleic acid that composes ribonucleotides. rRNA is present in the ribosome, hence the name ribosomal RNA. In other words, rRNA is the RNA component of a ribosome. Therefore, the basic functions of rRNA are associated with the function of ribosome: protein synthesis inside a cell. During the protein synthesis, rRNA governs the decoding of messenger RNA into amino acids with its mechanism. In addition, rRNA interacts with transfer RNA during translation during the conversion of the base sequence of the nucleic acid (nucleotide sequence) into a protein molecule.

rRNA occurs as two subunits known as the large subunit (LSU) and the small subunit (SSU) in the ribosome. During protein synthesis, small subunit read the mRNA strand while the large subunit assembles the protein molecule. However, it would be interesting to know that the messenger RNA strand is progressed through the two subunits, often sandwiched between SSU and LSU, while the formation of peptide bond in the protein molecule is catalyzed by the ribosome. In addition, rRNAs being nucleic acids with nucleotide sequences, these could be regarded as reserves of genetic material.

What are Ribosomes?

Ribosomes are amongst the smallest organelles in a cell with a size of about 20 nanometers. Despite its small size compared to other organelles, it constitutes of complex and large molecules of RNA and proteins, which play vital roles in the process of protein synthesis. These complex RNA and proteins are collectively referred to as ribonucleic proteins.

Ribosomes are present in all the living cells including both prokaryotes and eukaryotes. However, prokaryotic and eukaryotic ribosomes differ structurally with each other. Prokaryotic ribosomes are 70S while eukaryotic ribosomes are 80S. Ribosomes are predominantly found attached to RER (rough endoplasmic reticulum) and rarely as free organelles in the cytoplasm. However, the attachment of ribosomes with RER is not permanent since the attachment is in a state of attached and detached with RER surface.

The main function of ribosomes is to catalyze the formation of the peptide bond between two amino acids according to the order of codons in the messenger RNA sequence. In fact, ribosome binds with the messenger RNA strand and uses it as a template to understand the correct sequence of amino acids in each protein molecule. Thus, its function in protein synthesis is vital. It would be also interesting to notice that there may be more than one ribosome in function at a particular time in identifying the nucleotide sequences of messenger RNA to determine the corresponding amino acid sequence.

What are the Similarities Between rRNA and Ribosomes?

• • rRNA is the RNA component of the ribosome.
  • Both rRNA and ribosomes are essential for protein synthesis in all living organisms.
  • They are in the cytoplasm.

What is the Difference Between rRNA and Ribosomes?

rRNA is a type of nucleic acid whereas ribosome is an organelle. Therefore, we can consider this as the key difference between rRNA and ribosomes. Furthermore, nucleotides make up the rRNA while RNA and proteins called ribonucleic proteins make up the ribosomes. Thus, this is a significant difference between rRNA and ribosomes in the make up. Moreover, rRNA could be sometimes used as a reserve of genetic material but not ribosomes. So, this is also a difference between rRNA and ribosomes.

Below infographic summarizes the difference between rRNA and ribosomes.

Summary – RNA vs Ribosomes

Ribosomes are small organelles present in both prokaryotic and eukaryotic cells. This organelle is extremely important since it is the organelle that carries out protein synthesis of the cell. Ribosomes have two components as rRNA and proteins. Hence, rRNA is the ribosomal RNA which is a component of ribosomes. rRNA is composed of ribonucleotides. rRNA is responsible for reading the correct order of codons in the mRNA sequence and linking amino acids together according to it. On the other hand, ribosome is responsible for the overall process of protein synthesis. This summarizes the difference between rRNA and ribosomes.

Reference:

1. “Ribosomal RNA.” Wikipedia, Wikimedia Foundation, 17 Jan. 2019, Available here.
2. Nature News, Nature Publishing Group, Available here.

Image Courtesy:

1. “Ribosome Translation” By CNX OpenStax – (CC BY 4.0) via Commons Wikimedia
2. “Ribosome shape” By Vossman – Own work (CC BY-SA 3.0) via Commons Wikimedia