Identify the role of all molecular constituents present in a functional polyribosome.
The correct answer and explanation is:
A functional polyribosome, also called a polysome, is a complex formed by multiple ribosomes translating a single mRNA strand simultaneously. The main molecular constituents of a polyribosome include the mRNA, ribosomes, tRNAs, and amino acids. Each plays a specific role in the process of translation, which is the synthesis of proteins from an mRNA template.
- mRNA (messenger RNA): The mRNA serves as the template for protein synthesis. It carries the genetic instructions from the DNA in the nucleus to the ribosomes in the cytoplasm, where it is translated into a specific sequence of amino acids. Each polyribosome is associated with one mRNA molecule, and as ribosomes move along it, they read the codons (three-nucleotide sequences) to build the protein chain.
- Ribosomes: The ribosomes are the molecular machines that carry out the translation process. They consist of two subunits: the large and small subunits. The small subunit binds to the mRNA, while the large subunit is responsible for the formation of peptide bonds between amino acids. Ribosomes move along the mRNA, translating the codons into a growing polypeptide chain. In a polyribosome, multiple ribosomes simultaneously translate the same mRNA molecule, increasing the efficiency of protein synthesis.
- tRNA (transfer RNA): The tRNA molecules are responsible for bringing amino acids to the ribosome during translation. Each tRNA has an anticodon region that recognizes and binds to the complementary codons on the mRNA, and a corresponding amino acid attached to the other end. The ribosome helps facilitate the attachment of the correct amino acid to the growing protein chain, based on the mRNA codon sequence.
- Amino acids: Amino acids are the building blocks of proteins. They are linked together by peptide bonds to form a polypeptide chain, which eventually folds into a functional protein. Amino acids are supplied to the ribosome by tRNA molecules that match the mRNA codons.
This coordinated interaction between the mRNA, ribosomes, tRNAs, and amino acids ensures the efficient and accurate synthesis of proteins within the cell.