Question

Where are polysomes found?

Answer 1

Hint: Groups of ribosomes which are bound in mRNA like beads on strings are known as polysomes. Ribosomes are macromolecular machines which are found in almost every cell which performs the synthesis of biological proteins.

Complete answer:
A macromolecular machine whose main function is to synthesize biological proteins also known as translation of mRNA is known as ribosome. Ribosomes consist of two subunits, a larger and a smaller one. Each unit contains many ribosomalRNA (rRNA) and ribosomal proteins.
Polysomes are mRNA bound with ribosomes like beads on strings. Polysomes are also known as polyribosomes or ergosomes. It consists of complex mRNA molecules and ribosomes which translate mRNA to polypeptides. During the elongation phase, when ribosomes and elongation factors synthesize, polysomes are formed. Polysome activity is used to measure the level of gene expression by a technique called polysomal profiling.
Polysomes are present mostly in rapidly fixing liver tissues. Glycogen polymer of glucose serves as storage of cytoplasm of hepatocytes and other cells. Hepatocytes vary in the amount of glycogen which is present in their cytoplasm. Under the microscope, polysomes appear as basophilic cytoplasmic granules but they are extremely liable during post mortem change in the liver.

Thus, A polysome is an mRNA that is attached to a large number of ribosomes that are involved in protein synthesis. It can be found in the cytoplasm or on the endoplasmic reticulum.

Note:
Polysomes, also known as polyribosomes, are divided into two categories in eukaryotic cells. A polysome is made up of a single mRNA and several ribosomes, with one ribosome for every 100 nucleotides or so. A ribosome in a eukaryotic cell takes about 30 seconds to synthesize a 400-amino-acid protein.