70S ribosomes

Definition

70S ribosomes are a type of ribosome found in prokaryotic cells, characterized by their sedimentation coefficient of 70S, which reflects their size and density. These ribosomes are essential for protein synthesis, translating messenger RNA (mRNA) into polypeptide chains by facilitating the binding of transfer RNA (tRNA) and the ribosomal subunits during translation. The 'S' stands for Svedberg units, which measure how fast particles sediment in a centrifugal field, indicating that 70S ribosomes are smaller than the 80S ribosomes found in eukaryotic cells.

5 Must Know Facts For Your Next Test

1. 70S ribosomes consist of two subunits: a smaller 30S subunit and a larger 50S subunit, each composed of rRNA and proteins.
2. The size and composition of 70S ribosomes allow them to efficiently synthesize proteins necessary for the growth and function of prokaryotic cells.
3. In addition to prokaryotes, 70S ribosomes can also be found in organelles like mitochondria and chloroplasts, suggesting an evolutionary link to ancient prokaryotic organisms.
4. The process of translation in prokaryotes occurs simultaneously with transcription, allowing for rapid protein production.
5. Antibiotics such as streptomycin target 70S ribosomes specifically, disrupting protein synthesis in bacteria while leaving eukaryotic ribosomes unaffected.

Review Questions

• How do the structural components of 70S ribosomes contribute to their function in protein synthesis?
  • The structural components of 70S ribosomes, including the 30S and 50S subunits, work together to create an environment where mRNA can be accurately translated into proteins. The small 30S subunit binds to the mRNA and ensures that the correct tRNA molecules bring the appropriate amino acids to the growing polypeptide chain. Meanwhile, the larger 50S subunit facilitates peptide bond formation between amino acids, effectively linking them together to form functional proteins.
• Discuss the implications of targeting 70S ribosomes with antibiotics for bacterial infections.
  • Targeting 70S ribosomes with antibiotics is crucial in treating bacterial infections because it selectively disrupts protein synthesis in bacteria without affecting human cells. Since human cells have 80S ribosomes, antibiotics can inhibit bacterial growth by blocking their ability to produce essential proteins needed for survival. This specificity is vital for minimizing side effects and ensuring effective treatment, making it a strategic approach in combating antibiotic-resistant bacteria.
• Evaluate the evolutionary significance of the presence of 70S ribosomes in mitochondria and chloroplasts.
  • The presence of 70S ribosomes in mitochondria and chloroplasts highlights their evolutionary significance as these organelles are believed to have originated from ancient prokaryotic ancestors through endosymbiosis. This relationship suggests that they retain features similar to prokaryotes, allowing them to independently synthesize some proteins necessary for their function. The retention of 70S ribosomes supports the idea that these organelles evolved from free-living bacteria, emphasizing the shared evolutionary history between eukaryotic cells and their prokaryotic relatives.

Related terms

Ribosomal RNA (rRNA): A type of RNA that makes up the structural and functional components of ribosomes, playing a critical role in protein synthesis.

Translation: The process by which ribosomes synthesize proteins by decoding the sequence of mRNA into a polypeptide chain.

Amino acids: The building blocks of proteins that are linked together in a specific sequence during translation to form polypeptides.