Cell Biology

Vacuoles are membrane-bound and contain water and excretory substances.

(A) It is membrane bound and contains storage proteins and lipids - Incorrect: While vacuoles are membrane-bound, they primarily store water, not proteins/lipids.

(B) It is membrane bound and contains water and excretory substances - Correct: Vacuoles are tonoplast-bound organelles containing cell sap with water, ions, and waste products.

(C) It lacks membrane and contains air - Incorrect: Vacuoles always have membranes (tonoplast).

(D) It lacks membrane and contains water and excretory substances - Incorrect: All vacuoles are membrane-bound structures.

The correct answer is (B), as vacuoles are membrane-bound sacs containing cell sap with water and metabolic wastes.