80S ribosomes

Definition

80S ribosomes are the type of ribosomes found in eukaryotic cells, composed of a large 60S subunit and a small 40S subunit. They play a crucial role in protein synthesis by facilitating the translation of messenger RNA (mRNA) into polypeptide chains, which eventually fold into functional proteins. The 'S' in 80S refers to the Svedberg unit, a measure of the sedimentation rate during centrifugation, indicating the size and density of the ribosomal particles.

5 Must Know Facts For Your Next Test

1. 80S ribosomes are larger than prokaryotic 70S ribosomes, allowing for more complex interactions during protein synthesis.
2. The large 60S subunit contains three ribosomal RNA molecules and approximately 49 proteins, while the small 40S subunit contains one ribosomal RNA molecule and about 33 proteins.
3. Eukaryotic ribosomes are often found free-floating in the cytoplasm or attached to the endoplasmic reticulum, playing a role in both free and membrane-bound protein synthesis.
4. The Svedberg unit reflects the ribosome's shape and density rather than its molecular weight, which is why 80S is not simply the sum of its subunits' S values.
5. Ribosome biogenesis is a highly regulated process that involves multiple cellular compartments and requires coordination with other cellular activities like cell growth and division.

Review Questions

• How do 80S ribosomes differ from prokaryotic ribosomes in structure and function?
  • 80S ribosomes are distinct from prokaryotic 70S ribosomes primarily in their size and composition. The 80S structure consists of a larger 60S subunit and a smaller 40S subunit, whereas prokaryotic ribosomes have a smaller 50S large subunit and a 30S small subunit. This difference in size allows eukaryotic ribosomes to accommodate more complex protein synthesis processes, including post-translational modifications that often occur in eukaryotic cells.
• Discuss the significance of the Svedberg unit in relation to ribosomal function and how it relates to the sedimentation rate during centrifugation.
  • The Svedberg unit indicates how quickly particles, like ribosomes, sediment when subjected to centrifugal force, which is influenced by their size and shape. For example, an 80S ribosome sediments faster than smaller particles due to its larger mass. This sedimentation rate is critical for isolating ribosomal components during experiments, allowing researchers to study their functions and interactions during processes like translation, which is essential for protein synthesis.
• Evaluate the role of 80S ribosomes in eukaryotic cells and how their dysfunction could impact cellular processes.
  • 80S ribosomes play an essential role in translating mRNA into proteins, which are vital for various cellular functions. If these ribosomes malfunction or are improperly assembled, it can lead to incomplete or faulty proteins being synthesized. This dysfunction can disrupt critical cellular processes such as metabolism, signaling, and response to environmental changes, potentially leading to diseases like cancer or genetic disorders where protein synthesis is compromised. The implications are vast, highlighting the importance of proper ribosomal function in maintaining cellular health.

Related terms

Prokaryotic ribosomes: Ribosomes found in prokaryotic cells, typically composed of a 70S structure made up of a 50S large subunit and a 30S small subunit.

Translation: The process by which ribosomes synthesize proteins using the genetic information carried by mRNA.

Polypeptide:

A chain of amino acids linked by peptide bonds that fold into a functional protein after synthesis.