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| Front-side | Reverse-side |
|---|---|
| Do organelle ribosomes differ from cytosolic (i.e., ‘classic’ eukaryotic) ribosomes? How? | Organelle ribosomes are distinct from cytosolic; they often resemble prokaryotic ribosomes (70% RNA), though there are exceptions (as small as 60S; 30% RNA). |
| How large is a ribosome (both subunits)? | 200×220 angstroms, about the length of a 35 bp mRNA. |
| Movement of the ribosome along the mRNA during translation is called: | translocation |
| mRNA binds to which ribosomal subunit? | mRNA binds to the small subunit. |
| Peptide bond syntheses involves transfer of the nascent polypeptide from the ….................... to the …..................This is followed by ….................... | tRNA present in the P site; tRNA present in the A site; translocation |
| The deacylated tRNA leaves via the ….................., after which it is released into the….................. | E tRNA binding site; cytosol. |
| What are ribosome-associated proteins called? | r-proteins |
| What are the three stages of protein synthesis? | Initiation, elongation and termination. |
| What is present in the P site during protein synthesis, at the point that the A site binds an incoming charged tRNA? | The peptydl-tRNA (the ‘second’ tRNA, bound to the nascent polypeptide). |
| What is the RNA/protein composition of the _E. coli _30S ribosomal subunit? | 16S rRNA and 21 r-proteins. |
| What is the RNA/protein composition of the E. coli 50S ribosomal subunit? | 23S rRNA, 5S rRNA, and 31 r-proteins. |
| What is the RNA/protein composition of the eukaryotic 40S ribosomal subunit? | 18S, 33 r-proteins. |
| What is the RNA/protein composition of the eukaryotic 60S ribosomal subunit? | 28S, 5.8S and 5S rRNA, plus 49 r-proteins. |
| What two general types of errors can be made by the ribosome during translation? What is the consequence of each for the polypeptide? |
1) base skip (omitting a codon) or duplication (reading the same codon twice; failure of translocation?). Results in a shift of the reading frame. 2)Incorrect base addition (due to a, aminoacyl-tRNA mispair). Results in a single-residue error (analogous to a point mutation?). |
| Which ribosome site is bound by an incoming tRNA? | The A (acceptor?) site. |