Vaculoe

 A cell contains a nucleus and membrane bound organelles 

A vacuole is a membrane-bound sac found inside cells.

Its main job is to store materials. 

What it stores depends on the type of cell:

In plant cells: vacuoles are usually very large (called central vacuoles). They store water, nutrients, and waste products. They also help keep the plant rigid by maintaining turgor pressure (water pressure inside the cell).

In animal cells: vacuoles are smaller and more numerous. They help store nutrients, waste, or other small molecules, and sometimes assist in breaking down materials.

In unicellular organisms (like amoebas): some vacuoles pump out extra water (contractile vacuoles), while others help digest food (food vacuoles).

Practice : 

A cell contains a nucleus and membrane bound organelle