Page 3 - Lesson Notes

 In animals and young plant cells, sap vacuoles are small whereas in
mature plant cell there is a large central vacuole occupying 50-90% of cell

volume.
 The covering of the sap vacuole is called tonoplast.

 Sap vacuole stores salts, sugar, amino acids, organic acids and some

proteins.
Function

1. Provides rigidity and turgidity to the cell. Hence responsible for maintaining
the shape of plant cells. When the cell is full of water, the vacuole exerts

pressure outwards, pushing the cell membrane against the cell wall. This

pressure is called turgor pressure.
2. Dump organelle for waste products in plants.

3. Also, importance substances of plant cell are stored.
(b) Food vacuole

In some unicellular organisms, the sac containing ingested food particles fuse with
lysosomes to form food vacuole. Digestion takes place in food vacuole.

Figure- Food vacuole in Amoeba cell

(c) Contractile vacuole
These vacuoles are specialised to collect liquid from the cell, swell up, reach from

the surface, and burst to release their contents, thus they take part in osmoregulation
and excretion as in Amoeba, Paramecium.