Question

What is feedback inhibition ? Compare it with the mechanism of regulation based on operon model.

Answer 1

In feedback inhibition, the end product of a biosynthetic pathway inhibits the activity of the first enzyme that is unique to the pathway, thus controlling production of the end product. It is usually seen in eukaryotes.

While an operon is a cluster of functionally-related genes that are controlled by a shared operator. Operons consist of multiple genes grouped together with a promoter and an operator. Operons are present in prokaryotes (bacteria and archaea), but are absent in eukaryotes. Each operon contains regulatory DNA sequences, which act as binding sites for regulatory proteins that promote or inhibit transcription. Regulatory proteins often bind to small molecules, which can make the protein active or inactive by changing its ability to bind DNA. Some operons are inducible, meaning that they can be turned on by the presence of a particular small molecule. Others are repressible, meaning that they are on by default but can be turned off by a small molecule.