70s ribosomes

Definition

70s ribosomes are a type of ribosome found primarily in prokaryotic cells, consisting of a large 50s subunit and a small 30s subunit. These ribosomes are essential for protein synthesis, translating mRNA into polypeptides, and are distinguished from eukaryotic ribosomes, which are larger and designated as 80s. The 's' in 70s and 80s refers to the Svedberg unit, a measure of sedimentation rate that correlates with size and shape.

5 Must Know Facts For Your Next Test

1. 70s ribosomes are typically found in prokaryotes, such as bacteria and archaea, and play a critical role in their cellular metabolism.
2. The structure of 70s ribosomes allows them to efficiently bind to mRNA and tRNA during protein synthesis.
3. Antibiotics such as tetracycline specifically target the 70s ribosome, inhibiting bacterial protein synthesis without affecting eukaryotic cells.
4. 70s ribosomes can also be found in mitochondria and chloroplasts of eukaryotic cells, which are thought to have originated from ancient prokaryotic ancestors.
5. The difference between 70s and 80s ribosomes is significant in understanding the evolution of protein synthesis mechanisms across different life forms.

Review Questions

• Compare the structure of 70s ribosomes to that of 80s ribosomes and explain how these differences affect their function.
  • 70s ribosomes consist of a large 50s subunit and a small 30s subunit, while 80s ribosomes are made up of a large 60s subunit and a small 40s subunit. The smaller size of the 70s ribosome allows for quicker assembly and more efficient translation in prokaryotic cells. This structural difference is crucial for understanding why certain antibiotics can specifically target bacterial ribosomes without harming eukaryotic cells.
• Discuss the role of 70s ribosomes in prokaryotic protein synthesis and how they interact with mRNA during translation.
  • In prokaryotes, 70s ribosomes play an essential role in translating mRNA into proteins. They bind to the mRNA at the start codon, facilitating the correct positioning of tRNA molecules that bring amino acids. This interaction allows for the sequential addition of amino acids to form polypeptides, highlighting the efficiency of protein synthesis in prokaryotic cells, which can occur simultaneously with transcription.
• Evaluate the significance of targeting 70s ribosomes with antibiotics in medical treatment and how this reflects on evolutionary biology.
  • Targeting 70s ribosomes with antibiotics like streptomycin is significant because it allows for selective inhibition of bacterial protein synthesis without affecting human cells that contain 80s ribosomes. This selective targeting illustrates the evolutionary divergence between prokaryotic and eukaryotic organisms. Understanding this difference not only aids in developing effective treatments but also provides insights into the evolutionary history of cellular machinery.

Related terms

Eukaryotic ribosomes: Ribosomes found in eukaryotic cells, composed of larger 60s and 40s subunits, and responsible for synthesizing proteins in the cell.

mRNA: Messenger RNA, a type of RNA that carries genetic information from DNA to the ribosome, where it serves as a template for protein synthesis.

Translation: The process of synthesizing proteins from mRNA templates using ribosomes, tRNA, and various enzymes.