Question

In the lac operon model, lactose molecules function as
A. Inducers, which bind with the operator gene
B. Repressors, which bind with the operator gene
C. Inducers, which bind with the repressor protein
D. Corepressors, which bind with repressor protein

Answer 1

Hint: The lac operon is the commonly known form of the lactose operon which is a combination of genes that are specific for uptake and metabolism of lactose. Lac operon is present in E. coli and some other bacteria. The lac operon is made up of three structural genes, that are lacZ, lacY, and lac A.

Complete answer:
An operon is a unit of genomic DNA containing a group of genes and it is a functioning unit that is responsible for the transport and metabolism of lactose. The lactose operon is popularly known as lac operon. This type of operon is observed in E. coli and many other enteric bacteria.
The lac operon contains a set of genes which are used for coding the proteins for the purpose of transporting lactose into the cytosol and then digesting it into glucose. This glucose is then used to produce energy as required in the bacteria. It is worked only when lactose is present and glucose is absent.
There are three structural genes found in the lac operon that are LacZ, LacY, and LacA. The function of these genes is controlled by the two regulators. These regulators of genes turn the operon on and off in response to lactose and glucose levels. These regulators are known as the lac repressor and catabolite activator protein (CAP). The lac repressor acts as a lactose sensor and produces repressor protein.
Lactose present in the lac operon of E.coli is an example of the inducer and this is the substrate for the enzyme beta−galactosidase. The lactose which is known as inducer binds with the repressor protein. It is not capable of binding with the operator gene. After binding with the repressor protein lactose is converted into a non-DNA binding state which leads to the activation of the operon.

Therefore, the correct option is option C.

Note: The lac operon is the combination of genes present in prokaryotes like E. coli and many other enteric bacteria. This operon is mainly involved in lactose metabolism. In the lac operon, lactose molecules function as inducers and it binds with the repressor protein.