Question

List and describe the role of all molecular constituents present in a functional polyribosome.

Short answer

Answer: The main function of a polyribosome is to synthesize proteins more efficiently by allowing multiple ribosomes to translate the same messenger RNA (mRNA) simultaneously. Its molecular constituents, including mRNA, ribosomes, transfer RNA (tRNA), amino acids, initiation factors (IF), elongation factors (EF), and release factors (RF), play crucial roles in different stages of translation, contributing to efficient protein synthesis.

Step-by-step solution

Introducing Polyribosomes

A polyribosome, also known as a polysome, is a structure composed of multiple ribosomes attached to a single messenger RNA (mRNA) molecule. The function of a polyribosome is to synthesize proteins more efficiently by allowing multiple ribosomes to translate the mRNA simultaneously.

List of Molecular Constituents of Polyribosomes

The main molecular constituents present in a functional polyribosome are: 1. Messenger RNA (mRNA) 2. Ribosomes (Small and large subunit) 3. Transfer RNA (tRNA) 4. Amino acids 5. Initiation factors (IF) 6. Elongation factors (EF) 7. Release factors (RF)

Describing the Role of mRNA in Polyribosomes

Messenger RNA (mRNA) serves as the template that ribosomes read to translate the genetic information into a protein sequence. In a polyribosome, multiple ribosomes bind and translate the same mRNA molecule, increasing the efficiency of protein synthesis.

Describing the Role of Ribosomes in Polyribosomes

Ribosomes are the protein synthesizing machinery, composed of small and large subunits. In a polyribosome, multiple ribosomes bind to the mRNA and synthesize proteins simultaneously by moving along the mRNA molecule and translating the genetic information into a polypeptide chain.

Describing the Role of tRNA in Polyribosomes

Transfer RNA (tRNA) molecules act as adaptors that bring the amino acids to the ribosome, where they match the mRNA codon with the appropriate amino acid. In a polyribosome, tRNAs deliver amino acids to each ribosome translating the mRNA, contributing to the synthesis of the polypeptide chain.

Describing the Role of Amino Acids in Polyribosomes

Amino acids are the building blocks of proteins; they are linked together by peptide bonds to form the polypeptide chain. In a polyribosome, amino acids are delivered by tRNAs to the ribosome-mRNA complex, and they are incorporated into the growing polypeptide chain according to the genetic information encoded in the mRNA.

Describing the Role of Initiation Factors, Elongation Factors, and Release Factors in Polyribosomes

Translation involves three phases: initiation, elongation, and termination. Initiation factors (IF), elongation factors (EF), and release factors (RF) play crucial roles in the different stages of translation. 1. Initiation factors (IF): They are needed for ribosome-mRNA-tRNA complex formation during the initiation process of translation. They help establish the proper reading frame, ensuring the correct start codon is recognized. 2. Elongation factors (EF): They play roles in tRNA recruitment and translocation within the ribosome during the elongation phase of translation. They ensure the correct amino acid-tRNA pair is brought to the ribosome, and they assist in the movement of the ribosome along the mRNA. 3. Release factors (RF): They recognize stop codons in the mRNA and help in terminating the translation process. They release the newly synthesized polypeptide chain from the ribosome-mRNA complex, allowing the ribosome and mRNA to participate in another round of protein synthesis.