Question

Assembly of 60 S and 40 S subunits of ribosomes produce
(A) 80 S
(B) 70 S
(C) 50 S
(D) 100 S

Answer 1

Hint:The assembly of 60 S and 40 S subunits of ribosomes produces 80 S units. It is a characteristic feature of the eukaryotic cell. This type of ribosome is predominantly found in the nucleus of eukaryotic cells.

Complete answer:
Ribosomes are acting as macromolecular machines that are found within the living cells. It performs the function of the synthesis of biological protein. They help in linking amino acids together in the order specified by the codon of messenger RNA (mRNA) molecules that form polypeptide chains. The ribosomes comprise two essential components: smaller subunits and larger subunits.

Each of them is having one or more ribosomal RNA (rRNA). Eukaryotes have an 80 S type of ribosome which is formed by the assemblage of 60 S and 40 S subunits. This type of ribosome is localized in the cytosol of eukaryotic cells. 80 S eukaryotic ribosome is having larger subunits i.e. 60 S and smaller subunits i.e. 40 S. The 40 S unit consists of an 18 S RNA which is made up of 1900 nucleotides and 33 proteins.

The larger subunit (the 60S) is composed of a 5 S RNA (120nucleotide) and 28 S RNA (4700 nucleotides) and 5.8 S RNA (160 nucleotides) subunits and 46 proteins. Ribosomes may be having the first originated structure in the RNA world. Ribosomes may sometimes be known as “non – membranous organelles”. There is the presence of ribosomes on the surface of the endoplasmic reticulum that is known as “rough endoplasmic reticulum”.

Hence the correct answer is option ‘B’ 80 S.

Note:The assembling of 60 S and 40 S subunits leads to the formation of 80 S ribosomes which is a unique feature of eukaryotic organisms. The function of the ribosome is to form different types of protein. Ribosomes may be present in mitochondria and are regarded as “mitoribosomes” and in plastids such as chloroplasts regarded as “plastic ribosomes”.