Describe the types of vacuoles and its functions
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Type # 1. Sap Vacuoles:
They are fluid filled vacuoles or vesicles which are separated from the cytoplasm by a selectively permeable membrane called tonoplast. It has a number of transport systems for the passage of different substances. A number of small sap vacuoles occur in animal cells and young plant cells. In mature plant cells, the small vacuoles fuse to form a single large central vacuole which occupies up to 90% of the volume of the cell.
The large central vacuole spreads the cytoplasm in the form of a thin peripheral layer. This is a device to facilitate rapid exchange between cytoplasm and the surrounding environment. The fluid present in the sap vacuoles is often called sap or vacuolar sap. It contains mineral salts, sugars, amino acids, esters, proteins, waste products and water soluble pigments called anthocyanin’s.
Type # 2. Contractile Vacuoles:
They occur in some protistan and algal cells found mostly in fresh water. A contractile vacuole has a highly extensible and collapsible membrane. It is also connected to a few feeding canals (e.g., Paramecium). The feeding canals obtain water with or without waste products from the surrounding cytoplasm. They pour the same into the contractile vacuole.
The vacuole swells up. The process is called diastole. The swollen contractile vacuole comes in contact with plasma membrane and collapses. Collapsing is called systole. This throws the vacuolar contents to the outside. Contractile vacuoles take part in osmoregulation and excretion. Osmoregulation is required in fresh water habitats where water has tendency to enter the living cells.
Type # 3. Food Vacuoles:
They occur in the cells of protozoan protists, several lower animals and phagocytes of higher animals. A food vacuole is formed by fusion of phagosome and a lysosome. The food vacuole contains digestive enzymes with the help of which nutrients are digested. The digested materials pass out into the surrounding cytoplasm.
Type # 4. Air Vacuoles (Pseudo-vacuoles, Gas vacuoles):
They have been reported only in prokaryotes. An air vacuole is not a single entity, neither it is surrounded by a common membrane. It consists of a number of smaller sub-microscopic vesicles. Each vesicle is surrounded by a protein membrane and encloses metabolic gases. Air vacuoles not only store gases but provide buoyancy, mechanical strength and protection from harmful radiations.
They are fluid filled vacuoles or vesicles which are separated from the cytoplasm by a selectively permeable membrane called tonoplast. It has a number of transport systems for the passage of different substances. A number of small sap vacuoles occur in animal cells and young plant cells. In mature plant cells, the small vacuoles fuse to form a single large central vacuole which occupies up to 90% of the volume of the cell.
The large central vacuole spreads the cytoplasm in the form of a thin peripheral layer. This is a device to facilitate rapid exchange between cytoplasm and the surrounding environment. The fluid present in the sap vacuoles is often called sap or vacuolar sap. It contains mineral salts, sugars, amino acids, esters, proteins, waste products and water soluble pigments called anthocyanin’s.
Type # 2. Contractile Vacuoles:
They occur in some protistan and algal cells found mostly in fresh water. A contractile vacuole has a highly extensible and collapsible membrane. It is also connected to a few feeding canals (e.g., Paramecium). The feeding canals obtain water with or without waste products from the surrounding cytoplasm. They pour the same into the contractile vacuole.
The vacuole swells up. The process is called diastole. The swollen contractile vacuole comes in contact with plasma membrane and collapses. Collapsing is called systole. This throws the vacuolar contents to the outside. Contractile vacuoles take part in osmoregulation and excretion. Osmoregulation is required in fresh water habitats where water has tendency to enter the living cells.
Type # 3. Food Vacuoles:
They occur in the cells of protozoan protists, several lower animals and phagocytes of higher animals. A food vacuole is formed by fusion of phagosome and a lysosome. The food vacuole contains digestive enzymes with the help of which nutrients are digested. The digested materials pass out into the surrounding cytoplasm.
Type # 4. Air Vacuoles (Pseudo-vacuoles, Gas vacuoles):
They have been reported only in prokaryotes. An air vacuole is not a single entity, neither it is surrounded by a common membrane. It consists of a number of smaller sub-microscopic vesicles. Each vesicle is surrounded by a protein membrane and encloses metabolic gases. Air vacuoles not only store gases but provide buoyancy, mechanical strength and protection from harmful radiations.
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Answer:
A vacuole is a membrane bound, multifunctional organelle found in the cells of plants (including algae and fungi) and some protists and bacteria. Vacuoles are acidic in nature and share some basic properties with lysosomes that are predominantly found in plant cells.
Depending on the type of plant, there are different types of vacuoles with specific properties that are crucial to their functions.
* Unlike lysosomes in animals, there is only one of a few vacuoles in individual plant cells.
* Vacuoles take up 80-90 percent of the entire plant cell volume
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