VACUOLES (NON-CYTOPLASMIC INCLUSIONS)

VACUOLES (NON-CYTOPLASMIC INCLUSIONS)

Nature and Occurrence

• Vacuoles are fluid filled or solid filled single membrane bound spaces. They are storage sacs.
• In plant cells, a single prominent very large vacuole is present which occupies 50-90% of cell volume.
• In plant cell, vacuole is bound by a membrane called tonoplast, filled with cell sap (a watery solution rich in sugars, amino-acids, proteins, minerals, metabolic wastes etc.

Types of Vacuoles

• Food vacuoles : In Amoeba and amoeboid cells of higher animals the sacs containing ingested food particles fuse with lysosomes to form food vacuoles.
• Contractile vacuole : Occur in some unicellular fresh water organisms e.g. Amoeba, Paramoecuim. They perform the function of osmoregulation.

Structure of Vacuole

Functions

• Vacuoles play important role in expelling excess water and waste from the cell in unicellular organisms. This is called osmoregulation and excretion.
• They store and help in digestion of food in unicellular organisms (food vacuole).
• They store toxic metabolic by-products or end products of plant cells.
• They provide turgidity and rigidity to the plant cells.
• They are store houses of the cell. The storage products include amino acids, sugars various organic acids and some proteins.