Which answer option explains why rRNAs are the most abundant type of RNA in a mammalian cell?

• A. Ribosomal RNAs (rRNAs) are required in large quantities because they are the main structural and functional components of ribosomes, which are present in high numbers to support protein synthesis.
• B. rRNAs are more stable than other types of RNA, so they accumulate over time.
• C. rRNAs are produced as a byproduct of mRNA degradation.
• D. rRNAs function as enzymes in metabolic pathways, requiring high abundance.

Answer: (A)

Verified step by step guidance

1. Step 1: Understand the role of rRNAs in the cell. Ribosomal RNAs (rRNAs) are essential components of ribosomes, which are the molecular machines responsible for synthesizing proteins. Protein synthesis is a critical and constant process in mammalian cells, requiring a large number of ribosomes.
2. Step 2: Recognize the structural and functional importance of rRNAs. Ribosomes consist of both rRNAs and ribosomal proteins, with rRNAs forming the core structure and playing a direct role in catalyzing peptide bond formation during translation.
3. Step 3: Consider the abundance of ribosomes in mammalian cells. Mammalian cells contain thousands of ribosomes to meet the high demand for protein synthesis, especially in actively dividing or metabolically active cells. This explains why rRNAs, as key components of ribosomes, are produced in large quantities.
4. Step 4: Evaluate the stability of rRNAs compared to other types of RNA. rRNAs are more stable than mRNAs and tRNAs, which are more transient and degrade more quickly. This stability contributes to their accumulation in the cell over time.
5. Step 5: Eliminate incorrect options. rRNAs are not produced as a byproduct of mRNA degradation, nor do they function as enzymes in metabolic pathways. Their high abundance is directly tied to their role in ribosome structure and function, supporting protein synthesis.