Which of the following is the inducer of the lac operon in cells? Group of answer choiceslactose allolactosegalactoseglucoseisopropylthiogalactopyranoside

To determine the inducer of the lac operon in cells, we need to analyze the given options: lactose, allolactose, galactose, glucose, and isopropylthiogalactopyranoside (IPTG).

1. Lactose: Lactose is a disaccharide composed of glucose and galactose. It is known to be the natural inducer of the lac operon. When lactose is present in the cell, it can be converted into allolactose.

2. Allolactose: Allolactose is an isomer of lactose that is formed when lactose is present in the cell. It acts as an inducer by binding to the lac repressor protein and preventing it from binding to the operator region of the lac operon. This allows RNA polymerase to transcribe the genes involved in lactose metabolism.

3. Galactose: Galactose is a monosaccharide that is not directly involved in the induction of the lac operon. However, it can be converted into glucose-6-phosphate, which can then be used as a carbon source for energy production.

4. Glucose: Glucose is a monosaccharide that acts as a preferred carbon source for cells. When glucose is present in the cell, it inhibits the induction of the lac operon by preventing the formation of cyclic AMP (cAMP). cAMP is required for the binding of the cAMP receptor protein (CRP) to the lac operon, which enhances transcription.

5. Isopropylthiogalactopyranoside (IPTG): IPTG is a synthetic analog of lactose that is commonly used in laboratory experiments to induce the lac operon. It is not naturally occurring in cells but can mimic the effects of allolactose by binding to the lac repressor protein and preventing its binding to the operator region.

Based on this information, the correct answer for the inducer of the lac operon in cells is allolactose.