Question

Chemical nature of ribosomes is?

Answer 1

Ribosome is defined as the granular structure that was first observed under the electron microscope as dense particles by George Palade (1953). They are made up of ribonucleic acid (RNA) and proteins and are not surrounded by any membrane.

Complete answer:
Location: Ribosomes are mainly located in all kinds of cells prokaryotic as well as eukaryotic. In prokaryotic cells, they are present freely in the cytoplasm. In a eukaryotic cell, they are present free in the cytoplasmic matrix and also attached to the outer surface of the rough endoplasmic reticulum and nuclear envelope. The ribosome is defined as actively synthesizing cells, such as liver cells, pancreatic cells, endocrine cells, lymphocytes, and meristematic cells. The ribosomes are also located in the matrix of mitochondria and the stroma of plastids in the eukaryotic cells.

Types of the ribosome: The eukaryotic ribosome is the 80S kind and that of the prokaryotic ribosome is 70S. Here s is used for the sedimentation coefficient it is indirectly a measure of density and size. Both 70S and 80S are made of two subunits.
Chemical composition: A ribosome is composed of a highly folded rRNA molecule and many attached proteins and $\mathop {Mg}\nolimits^{2 + }$ ions. The ribosomes are composed of proteins and RNA (rRNA). Usually, three to four rRNA molecules and about forty to eighty different ribosomal proteins are observed in the ribosomes.

Functions of ribosomes:
Ribosomes play a role in providing space for the synthesis of proteins in the cell. Hence these are termed as protein factories of the cell. Ribosome furnishes enzymes and factors required for the formation of polypeptides. Ribosome also gives sites for the attachment of tRNA and mRNA which participate in protein synthesis and they help to form the site for the synthesis of the polypeptide.

Note: Escherichia coli cell may have and constitute 20,000 to 30,000 ribosomes and a eukaryotic cell may contain up to half a million ribosomes. Svedberg's constant represents their sedimentation rate.