70s ribosome

Definition

The 70s ribosome is a type of ribosome found in prokaryotic cells, consisting of a large 50s subunit and a small 30s subunit. This structure is crucial for protein synthesis, as it facilitates the translation of messenger RNA (mRNA) into polypeptide chains. The 70s ribosome plays a key role in various cellular processes, including the assembly of amino acids into proteins based on the genetic instructions carried by mRNA.

5 Must Know Facts For Your Next Test

1. 70s ribosomes are smaller than the eukaryotic 80s ribosomes and are essential for protein synthesis in prokaryotes like bacteria.
2. The 's' in 70s refers to Svedberg units, which measure the sedimentation rate during centrifugation, indicating their size and density.
3. Each subunit of the 70s ribosome is made up of ribosomal RNA (rRNA) and proteins, contributing to its structure and function in translation.
4. Inhibitors such as antibiotics can target bacterial 70s ribosomes, disrupting protein synthesis and effectively treating bacterial infections.
5. 70s ribosomes can also be found in mitochondria and chloroplasts of eukaryotic cells, reflecting their evolutionary origin from prokaryotes.

Review Questions

• How does the structure of the 70s ribosome facilitate its function in protein synthesis?
  • The structure of the 70s ribosome is designed to efficiently facilitate protein synthesis. The large 50s subunit and small 30s subunit work together to decode mRNA and assemble amino acids into polypeptides. The 30s subunit recognizes the start codon on mRNA, while the 50s subunit catalyzes the formation of peptide bonds between amino acids, ensuring a seamless translation process.
• Discuss how antibiotics can selectively target the 70s ribosome in bacteria without affecting eukaryotic cells.
  • Antibiotics are designed to exploit the structural differences between prokaryotic 70s ribosomes and eukaryotic 80s ribosomes. By targeting specific components or functions of the 70s ribosome, such as inhibiting peptide bond formation or disrupting mRNA binding, these drugs effectively halt protein synthesis in bacteria while leaving eukaryotic cells unharmed. This selectivity is crucial for treating bacterial infections without harming the host's own cells.
• Evaluate the evolutionary significance of the presence of 70s ribosomes in mitochondria and chloroplasts of eukaryotic cells.
  • The presence of 70s ribosomes in mitochondria and chloroplasts provides strong evidence for endosymbiotic theory, which suggests that these organelles originated from ancient prokaryotic cells. By retaining their prokaryotic-type ribosomes, these organelles maintain a level of autonomy in protein synthesis that is distinct from the nuclear-encoded processes found in eukaryotic cytoplasm. This evolutionary relationship highlights how mitochondria and chloroplasts contribute to cellular functions while preserving remnants of their prokaryotic ancestry.

Related terms

70s ribosome subunits: The two distinct components of the 70s ribosome, with the 50s subunit containing ribosomal RNA and proteins, while the 30s subunit contains its own ribosomal RNA and proteins.

Polypeptide:

A chain of amino acids linked together by peptide bonds, which is synthesized during the process of translation on the ribosome.

Translation: The process by which ribosomes synthesize proteins by decoding the mRNA sequence into a specific sequence of amino acids.