Biology Fundamental unit of life Part : 8

 

 

                                           Biology

                         Class – 9

             Fundamental unit of life

                            Part – 8 

# Vacuoles

·       Vacuoles are membrane bound sacs for storage of solid or liquid contents.

·       Vacuoles are small size in animal clls and large size in plant cells.

·       The central vacuole of some plants cells may occupy 50-90% of the cell volume due to which nucleus and other cell organelles are pushed to the sides.

#Types of vacuoles

1.    Sap vacuoles:

Ø These are the most common type’s vacuoles.

Ø They contain cell sap.

Ø The sap vacuoles bounded by a membrane called tonoplast.

Ø These vacuoles store amino acids, sugars, various organic acids and some proteins.

Ø They provide turgidity and rigidity to the plant cell and are also required absorption of water.

2.    Contractile vacuoles:

Ø These vacuoles help in osmoregulation, maintenance of water and salts balance in unicellular organisms like Paramoecium and Amoeba.

3.     Food vacuoles:

Ø These vacuoles are found in some unicellular organisms like Amoeba and other protozoans.

Ø These vacuoles contain food particles ingested by the process of phagocytosis.

Ø They also contain digestive enzymes which digest the complex food particles into small, simpler particles.

4.     Gas vacuoles:

Ø These vacuoles occur in some prokaryotes.

Ø They contain metabolic gases which help in maintaining buoyancy of the cell.

Ø They are not surrounded by any membrane.

# Functions of vacuoles

      i.          Help in osmoregulation and excretion.

    ii.          Help in storage of a number of substances like salt, sugar, amino acid, organic acid and some proteins.

  iii.          They function as dump house of waste products in plant cells.

  iv.          Provide turgidity and rigidity to the plant cells.

     v.          Maintain osmotic concentration of cytoplasm required for absorption of water in plant cells.