#INTRODUCTION:
-> Vacuoles are membrane bound sacs .
-> They are present in the cytoplasm of both plant and animal cell .
-> They actually like storage bubbles that hold water nutrients and waste products.
-> Vacuoles are much larger in size in plant cell as compared to animal cells .
# STRUCTURE :
A) SHAPE AND SIZE :
-> In plant cell there is usually one large central vacuole that can occupy upto 90% of the cell volume.
-> In animal cells the vacuoles are small and numerous.
B) MEMBRANE :
-> The vacuole is surrounded by single membrane called tonoplast . It is selectively permeable membrane .
[Note; selective permeable means it allows only certain molecules to pass in or out . ]
C) VACUOLAR FLUID :
-> The inside of Vacuole is filled with cell sap and waste of toxins .
D) ORIGIN OF VACUOLE :
-> Vacuoles are form by fusion of vesicle from endoplasmic reticulum and golgi apparatus.
# FUNCTIONS :
1) In plant cells ;
A) STORAGE :
-> It stores nutrients, sugars , amino acids , organic acids and ions .
-> It also store waste products and toxic substances to protect cytoplasm.
B) MAINTAIN TURGOR PRESSURE :
-> The Vacuole helps to maintain turgidity by storing water as it pushed the cytoplasm against the cell wall helping plants to stay upright.
C) pH AND IONIC STRENGTH :
-> It maintains the acidic environment ( pH approx 5 ) inside the Vacuoles which regulates ions concentration within the cell.
D) DIGESTION AND BREAKDOWN :
-> They contain hydrolytic enzymes that help to breakdown macromolecules .
E) PIGMENT STORAGE :
-> They store pigments Anthocyanins which gives colour to the flower , fruit and leaf of the plant .
F) WASTE DISPOSAL :
-> They actually as the dumping ground for waste and harmful materials.
G) DEFENSE :
-> Some Vacuoles contains toxic compounds or secondary metabolites that deter herbivores or pathogen.
2) In animal cells ;
A) ENDOCYTOSIS AND EXOCYTOSIS SUPPORT :
-> They help in uptake of materials and release of waste by fusing with the plasma membrane.
B) STORAGE AND TRANSPORT :
-> Temporary storage of nutrients and ions help in transport of substances within the cell .
C) OSMOREGULATION :
-> They maintain water balance within the cell .
D) PHAGOCYTIC VACUOLES : ( Food Vacuoles)
-> They are formed when amoeba or white blood cells engulf food or foreign material .
3) In unicellular organisms ; ( protozoa)
A) CONTRACTILE VACUOLES :
-> It is present in amoeba and paramecium and regulates water balance by expelling excess water ( prevents bursting ).
-> They are important for osmoregulation.
B) FOOD VACUOLES :
-> They are formed after engulfing food particles in which enzyme digest the food vacuole.
At last ,the vacuole acts as the cell’s multi-purpose storage and support hub, essential for maintaining structural integrity and internal balance.
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