Final answer:
The key catalytic sites in the ribosome are composed of both RNA and protein.
Step-by-step explanation:
Ribosomes are composed of rRNA and protein. rRNA is a major constituent of ribosomes, composing up to about 60% of the ribosome by mass and providing the location where the mRNA binds. The rRNA ensures the proper alignment of the mRNA, tRNA, and the ribosomes and has enzymatic activity, catalyzing the formation of peptide bonds during protein synthesis. Therefore, the key catalytic sites in the ribosome are composed of Both RNA and protein.