Consider statements about human nutrition: 1. Fats provide more energy per gram than carbohydrates. 2. Roughage prevents constipation. 3. Water is not considered a nutrient. Which are correct? MCQ with Answer and Explanation

Explanation:
Vitamin A (retinal) combines with opsin to form rhodopsin, the visual pigment in rod cells for dim-light vision. Deficiency causes night blindness.

Explanation:
Aerenchyma is a specialized parenchyma tissue with large intercellular air spaces, providing buoyancy and facilitating gas exchange in aquatic plants. It also helps in oxygen transport to submerged roots. Sclerenchyma is supportive, collenchyma flexible support, xylem water-conducting.

Explanation:
In the lac operon, the 'i' gene (regulatory gene) constitutively produces a repressor protein. In the absence of lactose (the inducer), this active repressor binds specifically to the operator region of the operon. The operator overlaps with the promoter, physically blocking RNA polymerase from binding to the promoter or moving forward to transcribe the structural genes (z, y, a). When lactose is present, it binds to the repressor, inactivating it and allowing transcription.