Ribosome

Definition

A ribosome is a molecular machine found within all living cells that serves as the site of protein synthesis, translating messenger RNA (mRNA) into polypeptide chains. These structures are composed of ribosomal RNA (rRNA) and proteins, and can be found either freely floating in the cytoplasm or attached to the endoplasmic reticulum. Ribosomes play a critical role in the process of translation, where they decode the genetic information carried by mRNA to assemble amino acids into functional proteins.

5 Must Know Facts For Your Next Test

1. Ribosomes can exist as free ribosomes in the cytoplasm or bound to the endoplasmic reticulum, forming rough ER.
2. Each ribosome consists of two subunits, a large subunit and a small subunit, which come together during protein synthesis.
3. The ribosome has three binding sites for tRNA: A (aminoacyl), P (peptidyl), and E (exit), facilitating the translation process.
4. Ribosomes are found in both prokaryotic and eukaryotic cells, although their structure and size differ slightly between these two types of cells.
5. Ribosomal RNA makes up about 60% of the mass of a ribosome and plays an essential role in the ribosome's catalytic functions.

Review Questions

• How do ribosomes contribute to the process of protein synthesis?
  • Ribosomes are crucial for protein synthesis as they serve as the site where translation occurs. They read the sequence of codons in mRNA and facilitate the binding of transfer RNA (tRNA) that carries specific amino acids. This assembly line process results in the formation of polypeptide chains, which eventually fold into functional proteins. Without ribosomes, cells would not be able to produce proteins necessary for various cellular functions.
• Discuss the differences between prokaryotic and eukaryotic ribosomes, particularly in terms of structure and function.
  • Prokaryotic ribosomes are typically smaller than eukaryotic ribosomes, with a sedimentation coefficient of 70S compared to 80S in eukaryotes. The smaller subunit in prokaryotes consists of 16S rRNA, while eukaryotes have 18S rRNA. Functionally, while both types carry out protein synthesis, eukaryotic ribosomes are often associated with the endoplasmic reticulum and can undergo more complex regulation. These structural differences also influence the effectiveness of antibiotics that target bacterial ribosomes without affecting eukaryotic ones.
• Evaluate how alterations in ribosomal function might impact overall cellular health and organismal development.
  • Changes in ribosomal function can have profound effects on cellular health and organismal development. For instance, mutations in ribosomal proteins or rRNA can lead to ribosomopathies, which are diseases caused by dysfunctional ribosomes that impair protein synthesis. This can disrupt cell growth and differentiation processes, potentially leading to developmental disorders or increased susceptibility to diseases such as cancer. By understanding these impacts, researchers can develop targeted therapies to correct or mitigate these issues related to ribosomal dysfunction.

Related terms

mRNA: Messenger RNA is a type of RNA that conveys genetic information from DNA to the ribosome, where proteins are synthesized.

tRNA: Transfer RNA is a type of RNA that brings amino acids to the ribosome during protein synthesis, matching its anticodon with the corresponding codon on the mRNA.

Translation: Translation is the process by which the sequence of bases in mRNA is decoded to produce a specific sequence of amino acids in a polypeptide chain.