The main difference between free and attached ribosomes is that free ribosomes occur in the cytosol, whereas attached ribosomes occur bound to the exterior surface of the endoplasmic reticulum.
Free and attached ribosomes are two types of ribosomes that occur inside the cell. Also, ribosomes’ function is in protein production through translating messenger RNA.
Key Areas Covered
1. What are Ribosomes
– Definition, Structure, Function
2. What are Free Ribosomes
– Definition, Structure, Function
3. What are Attached Ribosomes
– Definition, Structure, Function
4. Similarities Between Free and Attached Ribosomes
– Outline of Common Features
4. Difference Between Free and Attached Ribosomes
– Comparison of Key Differences
Key Terms
Attached Ribosomes, Free Ribosomes
What are Ribosomes
Ribosomes are intracellular structures important for the synthesis of proteins. The process of protein synthesis is translation. Ribosomes can read the codon sequence in the messenger RNA and translate it into the amino acid sequence of a protein, depending on the genetic code.
Figure 1: Ribosome
Furthermore, the ribosome comprises ribosomal RNA (rRNA) and ribosomal proteins. Ribosomal proteins have no function in translation. However, they assemble rRNA to produce two subunits. These two subunits arrange together to form the translational apparatus of the ribosome. Prokaryotes and eukaryotes contain ribosomes in two sizes. They are 70S and 80S ribosomes, respectively. Eukaryotic organelles such as chloroplasts and mitochondria contain 70S ribosomes. Importantly, the function of ribosomes is to synthesize proteins depending on the information in messenger RNA. This process is called translation.
What are Free Ribosomes
Free ribosomes are ribosomes that occur free in the cytosol. The key feature of free ribosomes is that they produce proteins utilized inside the cell. In other words, the proteins produced by free ribosomes are essential for internal cellular activity. Also, the proteins produced by free ribosomes provide structural support, such as proteins in the cytoskeleton. Further, other proteins used by mitochondria and chloroplasts and proteins used for energy synthesis are examples of proteins produced by free ribosomes. Additionally, both individual and clumped ribosomes, called polyribosomes, can occur in the cytosol.
Figure 2: Attached Ribosomes to ER
What is Attached Ribosomes
Attached ribosomes are the ribosomes that are attached to the endoplasmic reticulum. Also, it makes rough endoplasmic reticulum. By contrast to the location of the free ribosomes, attached ribosomes occur close to the endoplasmic reticulum, which is a site for sorting proteins according to their function. Therefore, the secretory proteins produced by attached ribosomes can be easily exported into the endoplasmic reticulum. Digestive enzymes are an example of proteins the attached ribosomes produce. Notably, attached ribosomes synthesize them into the endoplasmic reticulum and are packed into the lysosomes.
Similarities Between Free and Attached Ribosomes
- Free and attached ribosomes are two forms that the ribosomes occur in the cell.
- They produce different proteins.
Difference Between Free and Attached Ribosomes
Definition
Free ribosomes refer to the ribosomes unattached to any cellular structure and float freely around in the cytosol. In contrast, attached ribosomes refer to small organelles attached to the surface of the endoplasmic reticulum.
Importance
Free ribosomes occur in the cytosol, while attached ribosomes are attached to the endoplasmic reticulum.
Type of Proteins Synthesized
Free ribosomes synthesize proteins mostly used within the cell, while attached ribosomes synthesize proteins for secretion.
Examples
Free ribosomes produce structural proteins and enzymes, while attached ribosomes produce digestive enzymes.
Conclusion
In brief, free and attached ribosomes are the two ribosome types that occur in cells. Importantly, their function is to translate proteins from messenger RNA. Free ribosomes occur in the cytosol. Also, they synthesize proteins mostly used within the cell. Structural proteins and enzymes are examples of proteins produced by free ribosomes. In comparison, attached ribosomes occur on the surface of the endoplasmic reticulum. Also, they synthesize proteins for secretion. Further, digestive enzymes are examples of proteins produced by attached ribosomes. Therefore, the main difference between free and attached ribosomes is their location and function.
References:
- Ribosome. Genome.gov. (n.d.-c).
Image Courtesy:
- “Ribosome Translation” By CNX OpenStax – Own Work (CC-BY 4.0) via Commons Wikimedia
- “OSC Microbio 03 04 Endomemb” By CNX OpenStax – Own work (CC-BY 4.0) via Commons Wikimedia
Leave a Reply