Definition of ribosomes
Large and complex molecular machine, found within all living cells, that serves as the primary site of biological protein synthesis.
Examples of ribosomes in the following topics:
- As mRNAs are transcribed a phenomenon of "stuck" or stalled ribosomes can occur.
- Ribosomes translating the mRNA eventually translate into the 3’poly-A tail region of transcripts and stalls.
- Ribosomes thus may become sequestered associated with the nonstop mRNA and would not be available to translate other mRNA molecules into proteins.
- There are two ways in which cells deal with stuck ribosomes, nonstop mediated decay (NSD) and Trans-translation.
- Nonstop mediated decay mediates this problem by both freeing the stalled ribosomes and marking the nonstop mRNA for degradation in the cell by nucleases.
- Ribosomes can get stuck on mRNAs, cells have ways of unsticking them.
- Ribosomes are tiny spherical organelles that make proteins by joining amino acids together.
- Many ribosomes are found free in the cytosol, while others are attached to the rough endoplasmic reticulum.
- In prokaryotes, ribosomes can be found in the cytosol as well.
- Ribosomes are not membrane bound.
- All prokaryotes have 70S (where S=Svedberg units) ribosomes while eukaryotes contain larger 80S ribosomes in their cytosol.
- Macromolecules Macromolecules found within bacterial cytoplasm include the nucleoid region, ribosomes, proteins, and enzymes.
- The ribosomes, similar to ribosomes in eukaryotes, are responsible for protein synthesis.
- Eukaryotes have multiple types of ribosomes, including the mitochondria and cytosol).
- The differences in structure allow some antibiotics to kill bacteria by inhibiting their ribosomes, while leaving human ribosomes unaffected.
- While there exists a wide range of peptides that are not synthesized by ribosomes, the term nonribosomal peptide typically refers to a very specific set of these as discussed in this article.
- Nonribosomal peptides are synthesized by nonribosomal peptide synthetases, which, unlike the ribosomes, are independent of messenger RNA.
- Sixteen S ribosomal RNA (or 16S rRNA) is a component of the 30S small subunit of prokaryotic ribosomes .
- Transcription and translation in archaea resemble these processes in eukaryotes more than in bacteria, with the archaean RNA polymerase and ribosomes being very close to their equivalents in eukaryotes.
- Positive-sense ssRNA viruses (Group IV) have their genome directly utilized as if it were mRNA, with host ribosomes translating it into a single protein which is modified by host and viral proteins to form the various proteins needed for replication.
- Ribosomes are their only type of organelle.
- Like the Planctomycetes species, Verrucomicrobia possess a compartmentalised cell plan with a condensed nucleoid and the ribosomes pirellulosome (enclosed by the intracytoplasmic membrane) and paryphoplasm compartment between the intracytoplasmic membrane and cytoplasmic membrane.