Question

Polyribosomes are aggregation of
A. Only rRNA
B. Peroxisomes
C. Several ribosome held together by a string of mRNA
D. Ribosome and rRNA

Answer 1

Hint: Ribosome plays a vital role in the synthesis of proteins. Ribosomes can be found in smaller and larger subunits. Smaller subunits contain mRNA. During the translation process, Ribosome grouped together. Polypeptide chains are formed on larger subunits. Transfer RNA attaches with the polypeptide chain.

Complete answer:
Ribosomes contain RNA and associated proteins that function to synthesize proteins. Proteins are the building blocks of the body. Proteins help to perform many cellular functions. Ribosomes are found floating in the cytoplasm. Some of the ribosome is also attached to the endoplasmic reticulum. Ribosomes may be found as monosome or polysome. During the active protein synthesis, different types of ribosomes are found.
The group of ribosomes bound to an mRNA molecule and called as polyribosomes. It appears as beads on a thread. mRNA helps in the process of translation. When the ribosomes and elongation factors synthesize the encoded polypeptide, polysomes are formed. Many ribosomes move along the coding region of mRNA, creating polysomes. Smaller subunits carry mRNA while the larger subunits consist of tRNA.
The rRNA is the ribosomal RNA. Peroxisomes are the organelles which help in the lipid metabolism and chemical detoxification. It is also responsible for the oxidation reactions.
From the above information we have found that Polyribosomes are aggregation of several ribosomes held together by a string of mRNA.

Hence, the correct answer is option (C).

Note: The polysome structure of prokaryotes is different from the eukaryotic polysome and membrane bound polysomes. The prokaryotic polysome forms a double row structure. They contact each other through smaller subunits. The linear configuration is observed in eukaryotic polysomes. The endoplasmic reticulum which carries ribosomes is called a rough endoplasmic reticulum.