Ribozymes Group of answer choices Are RNAs with catalytic activity Are found in bacteria, but not eukaryotic cells May have evolved later than protein enzymes All of the above
The Correct Answer and Explanation is:
Correct answer: Are RNAs with catalytic activity
Explanation:
Ribozymes are RNA molecules that have the unique ability to catalyze specific biochemical reactions, similar to protein enzymes. The discovery of ribozymes challenged the traditional view that only proteins could function as enzymes. These RNA catalysts play vital roles in various cellular processes such as RNA splicing, replication, and protein synthesis.
One well-known ribozyme is the self-splicing intron, where a segment of RNA removes itself from a longer RNA molecule without the help of proteins. Another is the ribosome itself, particularly the large subunit, which catalyzes the formation of peptide bonds during protein synthesis. This reaction is carried out by the ribosomal RNA (rRNA), not the proteins in the ribosome. This means that the ribosome can be regarded, in part, as a ribozyme.
Ribozymes are found in both bacteria and eukaryotic cells, contradicting the second choice in the question. For example, the hammerhead ribozyme, first discovered in some plant viruses, has since been found in various organisms across all domains of life. Similarly, RNase P, which processes tRNA molecules, is found in bacteria, archaea, and eukaryotes and contains an essential RNA component that acts as the catalyst.
Regarding the third statement, it is more likely that ribozymes evolved earlier than protein enzymes. The RNA world hypothesis suggests that early life forms may have relied solely on RNA for both genetic information and catalytic functions before proteins and DNA became predominant. This implies that ribozymes are ancient molecules that may have existed before protein-based enzymes.
In summary, ribozymes are RNAs with catalytic activity, they are present in both bacteria and eukaryotes, and they likely predate protein enzymes in evolutionary history. Thus, only the first statement is correct.
