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Karteikarten von Marissa Alvarez, aktualisiert more than 1 year ago
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Erstellt von Marissa Alvarez
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| The ribosome Learning objectives: understand the following concepts | • Definition of a ribosome and its physiological role • The two major ribosomal subunits- small subunit (SSU) and large subunit (LSU) • Role of ribosomal RNA (rRNA) • Formation of SSU and LSU from rRNA and ribosomal proteins • Composition of interface and solvent surfaces of SSU and LSU |
| Overview about ribosomes Ribosomes: molecular machines made of __ and ribosomal ___. Physiological role: synthesizing ___ from amino acids. The number of ribosomes in a cell depends on the activity of the cell. Ribosomes are freely suspended in the cytoplasm or attached to the endoplasmic reticulum forming the ___ endoplasmic reticulum. Both prokaryotes and eukaryotes contain multiple copies of rRNA genes with strong promoters. On average, in a mammalian cell, there can be about 10 million ribosomes. | rRNA & proteins proteins rough |
| Additional overview of ribosomes • The ribosome is responsible for the final step of translating genetic codes into functional ___. • This molecular machine consists of two universally conserved subunits, the ___ subunit (__) and the ___ subunit (__), both of which are composed of rRNAs and ribosomal proteins. • In eukaryotes, the mature subunits are the ___ (SSU) and the __ (LSU), whereas in prokaryotes they are called __ (SSU) and ___ (LSU) • The biogenesis of ribosomes is a central cellular event that consumes significant amounts of metabolites and ___. • In addition to rRNA and r-protein components, the eukaryotic ribosomal subunit assembly requires >350 ___-ribosomal factors. • In eukaryotes, both the 40S and the 60S subunits are produced from a single pre-ribosomal particle known as the __ that is assembled in the ___. • The mature eukaryotic 80S ribosomes contain -5500 nucleotides of rRNA (SSU has 18S rRNA, while LSU has 5S, 5.8S, and 25S rRNA) and more than 80 proteins. **Ratio = __ rRNA and __ proteins | proteins small SSU large LSU 40S, 60S (eukaryotes) 30S, 50S (prokaryotes) energy non- 90S nucleolus 2/3 rRNA & 1/3 proteins |
| Slide showing composition of prokaryotic and eukaryotic ribosomes with molecular mass, number of nucleotides and proteins | |
| Ribosome assembly in prokaryotes • Binding of ribosomal proteins to the __ rRNA and RNase __ and __ digestion Additional ribosomal protein binding and maturation to ___ • Assembly of the 50S subunit follows a similar principle. Note that the pre-ribosomal RNA is transcribed from the ___ gene. | 16S and RNase III and M16 same 30S |
| Overview of eukaryotic ribosome synthesis and maturation Co-transcriptional binding of early trans-acting factors to the 35S rRNA forms the __ pre-ribosome. Cleavage at the __ site separates the pre-60S subunit (blue) and the pre-40S subunit (green), which undergo independent maturation pathways in the nucleoplasm and, eventually, in the cytoplasm. Final maturation in the ___ allows the joining of both subunits to form the functional __ ribosome. | 90S A2 cytoplasm 80S |
| Export of pre-ribosomes through the NPC (Nuclear Pore Complex) Channel All transport events between the nucleus and cytoplasm occur through the __ ___ ___ (__), which are composed of approximately __ proteins. |
nuclear pore complexes (NPCs)
30
Image:
Np Cs (binary/octet-stream)
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| The Ribosome is a ribozyme • The ribosome is __-__ rRNA and __-__ ribosomal protein • rRNA is considered to be responsible for the overall ___, for positioning tRNAs on mRNA, and for the formation of ___ bonds between amino acids. • The r-proteins are generally found on the surface and fill the __ and __ to stabilize the RNA __. • The ___ provides the framework on which the tRNAs are accurately matched to the codons of mRNA, while the __ catalyzes the formation of peptide bonds. • The SSU and the LSU are ___when not actively synthesizing proteins, and they join on an mRNA molecule. • To carryout coordinated movements required for efficient translation, a ribosome contains __ RNA binding sites one for mRNA and three for tRNAs (the A site, the P site, and the E site). | two-thirds one-third structure peptide gaps & crevices core SSU LSU separate four |
| Prokaryotes - rRNA forms skeleton of ribosomes through secondary and tertiary structures Note that __-___ within each rRNA leads to the formation of secondary and tertiary structures that serve as the skeleton for r-protein binding and ribosome formation | base-pairing |
| The 30S SSU composition of PROKARYOTES Interface view (mainly __): -16S rRNA colored gray -SSU ribosomal proteins colored distinctly and labeled (S plus a numeral) Solvent view: -Note that the SOLVENT surface is occupied mainly by ___ -SSU ribosomal proteins colored distinctly and labeled (S plus a numeral) | rRNA proteins |
| The 50S LSU composition of PROKARYOTES Interface view: -Note that the interface is mainly ___ (gray) Solvent view: -The solvent surface is mainly ___ (colored) -LSU proteins are labeled as L plus a numeral |
rRNA
protein
Image:
50 S (binary/octet-stream)
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| Eukaryotes - rRNA forms skeleton of ribosomes through secondary and tertiary structures Note that __ or __ and ___ base-pair to form secondary and tertiary structures that serve as the skeleton for r-protein binding and ribosome formation | 25S or 28S and 5.8S |
| The 40S SSU composition of EUKARYOTES Interface surface is mainly occupied by the 18S ___ (gray) with some colored proteins The solvent surface is occupied mainly by ___ colored distinctively and labeled (S plus numeral). e in the label refers to eukaryotic specific proteins while the rest are common between prokaryotes and eukaryotes | rRNA proteins |
| The 60S LSU composition of EUKARYOTES Interface surface is mainly occupied by the 28S ___ (gray) with some colored proteins The solvent surface is occupied mainly by ___ colored distinctively and labeled (L plus numeral). e in the label refers to eukaryotic specific proteins while the rest are common between prokaryotes and eukaryotes. | rRNA proteins |
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