-Which of the following statements about ribozymes is/are correct? a) Ribozymes are RNA molecules that function as enzymes. b) In some genes, intron RNA functions as a ribozyme and catalyzes its own excision. c) A ribosome can be regarded as one large ribozyme. d) All of the above
The Correct Answer and Explanation is:
Correct Answer: d) All of the above
All three statements about ribozymes are accurate.
Explanation:
Ribozymes are unique biological molecules because, unlike traditional enzymes made of proteins, ribozymes are composed of RNA. This was a groundbreaking discovery because it showed that RNA can have catalytic functions, not just act as a messenger of genetic information. Hence, statement (a) is true: ribozymes are RNA molecules that function as enzymes, meaning they can speed up chemical reactions, such as the cleavage and formation of phosphodiester bonds in RNA strands.
Statement (b) is also correct. Some genes contain introns, which are non-coding sequences that must be removed from RNA transcripts during processing. In some cases, the RNA segment itself—specifically the intron—can catalyze its own removal without the help of protein enzymes. This process is known as self-splicing and is one of the first pieces of evidence that RNA molecules can act enzymatically.
Statement (c) is true because the ribosome, the molecular machine that synthesizes proteins, includes a critical catalytic component made of RNA. The active site responsible for forming peptide bonds between amino acids is composed of ribosomal RNA, not protein. This RNA-based catalysis means that the ribosome can be considered a very large ribozyme. Specifically, the 23S rRNA in prokaryotic ribosomes and the 28S rRNA in eukaryotic ribosomes play this enzymatic role.
In conclusion, all the given statements describe important features of ribozymes. They highlight the versatility of RNA molecules in biological systems, showing that RNA can store genetic information and also catalyze essential biochemical reactions. This dual role supports the RNA world hypothesis, which proposes that early life may have relied solely on RNA before the evolution of DNA and proteins.
