70S ribosome

Definition

The 70S ribosome is a type of ribosome found in prokaryotic cells, consisting of a small 30S subunit and a larger 50S subunit. This structure is crucial for protein synthesis, where it facilitates the translation of mRNA into polypeptide chains. The '70S' designation refers to the sedimentation rate measured in Svedberg units, which reflects the ribosome's size and density.

5 Must Know Facts For Your Next Test

1. 70S ribosomes are found not only in bacteria but also in organelles like mitochondria and chloroplasts, which have similar structures to prokaryotic cells.
2. The 30S subunit contains 16S rRNA and about 21 proteins, while the 50S subunit consists of 5S and 23S rRNA along with approximately 34 proteins.
3. 70S ribosomes are essential for the proper functioning of prokaryotic cells, allowing them to quickly synthesize proteins necessary for survival and growth.
4. Antibiotics such as tetracycline and streptomycin specifically target 70S ribosomes, inhibiting protein synthesis in bacteria without affecting eukaryotic ribosomes.
5. The assembly of the 70S ribosome occurs through a complex series of steps involving rRNA and various initiation factors that ensure accurate translation.

Review Questions

• How do the components of the 70S ribosome contribute to its function in protein synthesis?
  • The 70S ribosome is made up of two subunits: the small 30S subunit and the larger 50S subunit. The 30S subunit is responsible for decoding the mRNA, while the 50S subunit catalyzes peptide bond formation between amino acids. Together, they facilitate the entire process of translation by providing a platform for tRNA molecules to bring amino acids in sequence as dictated by the mRNA, ultimately synthesizing proteins effectively.
• Discuss how the structure of the 70S ribosome differs from that of eukaryotic ribosomes and why these differences are significant.
  • The primary difference between the 70S ribosome and eukaryotic ribosomes (which are 80S) lies in their size and composition. Eukaryotic ribosomes contain a larger small subunit (40S) and large subunit (60S), along with different types of rRNA. These structural differences are significant because they allow for selective targeting by antibiotics that can inhibit bacterial protein synthesis without affecting eukaryotic cells, making them valuable in medicine.
• Evaluate the implications of targeting 70S ribosomes with antibiotics on bacterial resistance mechanisms.
  • Targeting 70S ribosomes with antibiotics can effectively halt bacterial growth by disrupting protein synthesis. However, bacteria can develop resistance through various mechanisms such as mutations in ribosomal RNA or proteins that alter the binding sites for antibiotics. Additionally, bacteria may produce enzymes that degrade antibiotics or use efflux pumps to expel them. Understanding these resistance mechanisms is crucial for developing new antibiotics and treatment strategies as antibiotic resistance continues to rise globally.

Related terms

Ribosomal RNA (rRNA): The type of RNA that combines with proteins to form ribosomes, playing a key role in the process of translation.

Messenger RNA (mRNA): A type of RNA that carries genetic information from DNA to the ribosome, serving as a template for protein synthesis.

Translation: The process by which ribosomes synthesize proteins by decoding the sequence of codons in mRNA.