The ribosome is important for catalyzing the formation of peptide bonds. Which of the following statements is true?
(a) The number of rRNA molecules that make up a ribosome greatly exceeds the number of protein molecules found in the ribosome.
(b) The large subunit of the ribosome is important for binding to the mRNA.
(c) The catalytic site for peptide bond formation is formed primarily from an rRNA.
(d) Once the large and small subunits of the ribosome assemble, they will not separate from each other until degraded by the proteasome.
Choice (c) is correct. A ribosome is built from many more proteins than rRNA molecules, although the ribosome is about two-thirds RNA and one-third protein by weight. Thus, (a) is incorrect. The small subunit binds to mRNA, so (b) is incorrect. Choice (d) is incorrect, as the assembly and disassembly of the small subunit with the large subunit occurs every time a protein is produced from an mRNA. When release factor binds to an mRNA, the ribosome will release the mRNA and dissociate into its two subunits, to be recycled during another round of protein synthesis.
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