Question

What type of RNA has the shortest lifetime in cells?

Short answer

Answer: Messenger RNA (mRNA) has the shortest lifetime in cells.

Step-by-step solution

Identify the three major types of RNA

The three main types of RNA that play important roles in cell biology are messenger RNA (mRNA), transfer RNA (tRNA), and ribosomal RNA (rRNA).

Understand the functions of the different RNA types

Messenger RNA (mRNA) carries genetic information from DNA to ribosomes where it is used as a template for protein synthesis. Transfer RNA (tRNA) serves as an adaptor molecule that reads the information in mRNA and brings the correct amino acid required for building the protein. Ribosomal RNA (rRNA) is a component of ribosomes and helps in the assembly and structure of ribosomes during protein synthesis.

Compare the lifetimes of the RNA types

Messenger RNA (mRNA) has a short lifetime as it degrades quickly after delivering its genetic information during protein synthesis. This allows for better regulation of gene expression, as the mRNA does not persist in the cell for long periods. Transfer RNA (tRNA) and ribosomal RNA (rRNA) have longer lifetimes in the cell because they are reused multiple times during protein synthesis.

Determine the RNA type with the shortest lifetime

From the comparison of lifetimes, messenger RNA (mRNA) has the shortest lifetime in cells, serving its purpose of transferring genetic information for protein synthesis before degrading.

Key concepts

Messenger RNA (mRNA)

Messenger RNA, commonly abbreviated as mRNA, is a crucial type of RNA that serves as the direct messenger between the DNA in the nucleus and the ribosomes, the protein-making machinery of the cell. Its primary role is to transfer genetic instructions from DNA to the ribosome, where proteins are synthesized. This process is known as transcription.

• Temporary Blueprint: mRNA molecules act as a temporary blueprint for protein synthesis. Once the necessary information is transcribed from DNA, the mRNA transports these instructions to the ribosome.
• Short-lived Nature: mRNA is designed to be short-lived within the cell. It degrades quickly after its job of conveying the genetic instructions is complete. This short lifespan allows cells to rapidly change the protein production profile in response to the environment or signals.

The transient nature of mRNA is important for cellular regulation, ensuring that proteins are only produced when and where they are needed. This way, the cell can adapt quickly to changing conditions.

Transfer RNA (tRNA)

Transfer RNA, abbreviated as tRNA, plays a critical role in the translation phase of protein synthesis. It acts as a molecular adaptor that translates the genetic code carried by messenger RNA into the specific sequence of amino acids that make up a protein.

• Adaptor Function: Each tRNA molecule has a specific region called an "anticodon" that is complementary to a codon on the mRNA. This ensures that the correct amino acid is added to the growing protein chain, corresponding to the genetic code.
• Stable and Reusable: Unlike mRNA, tRNA molecules are quite stable and can be reused. They remain in the cell to participate in numerous rounds of protein synthesis, which is efficient and conserves cellular resources.

The ability of tRNA to precisely match amino acids to mRNA codons is essential for the accurate translation of the genetic code, ensuring that proteins are built correctly each time.

Ribosomal RNA (rRNA)

Ribosomal RNA, or rRNA, is a fundamental component of ribosomes, which are the cellular structures where proteins are synthesized. rRNA combines with proteins to form the ribosome, creating an environment for mRNA and tRNA to meet and facilitate the translation of genetic information into proteins.

• Structural Role: rRNA helps maintain the structural integrity of ribosomes. Its unique folding properties aid in forming the core scaffold of the ribosome, providing a platform for mRNA and tRNA binding during protein synthesis.
• Catalytic Function: Besides its structural role, rRNA also catalyzes the formation of peptide bonds between amino acids, a critical step in building proteins.
• Long-lasting: Like tRNA, rRNA has a longer life span compared to mRNA. Ribosomes can be reused for multiple rounds of protein synthesis, making rRNA an essential and durable component of the cell.

The continuous and efficient functioning of rRNA is vital for sustaining the cell's protein manufacturing capabilities, supporting the diverse array of cellular functions necessary for life.