Questions & Answers

What are vacuoles? Name their types and functions.

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Hint: The majority of the structure of a living system is composed of carbohydrates, proteins, fats and nucleic acids. The composition of carbohydrates, proteins, fats and nucleic acids to find the majority of elements present in the body.

Step by step answer:Vacuoles are membrane-bound cavities found inside both eukaryotic and prokaryotic cells that often carry watery liquid or gases. These are small storage bundles which contain water with inorganic and organic substances. Contractile vacuole was the first discovered vacuole in protozoan. A vacuole is surrounded by a membrane called tonoplast, is biochemically similar to the cell membrane. Plant cell carries a single large-sized vacuole while an animal cell has multiple small vacuoles.

 Vacuoles are of 4 types:
Sap Vacuole: Several small sap vacuoles occur in animal cells and young plant cells. In plant cells, small vacuoles fuse to form a single large central vacuole that occupies the maximum volume of the cell. It facilitates rapid exchange between the cytoplasm and the surrounding environment. The fluid present in the sap vacuoles is often called a sap or vacuole sap.
Contractile Vacuoles: They occur in some protistan and algal cells found mostly in freshwater. It has a highly extensible and collapsible membrane. They pour the same into the contractile vacuole. The vacuole swells up (diastole). The swollen contractile vacuole comes in contact with the plasma membrane and collapses (systole). This throws the vacuole contents to the outside. Contractile vacuoles are imperative for osmoregulation and excretion.

Food Vacuoles: These vacuoles occur in the cells of protozoan protists, some lower animals, and phagocytic higher animals. A food vacuole originates from the fusion of a phagosome and a lysosome. The food vacuole contains digestive enzymes for the breakdown of the nutrients. The digested materials are passed out into the surrounding cytoplasm.
Air Vacuoles (Pseudo-vacuoles, Gas vacuoles): Found in prokaryotes, they are not a single entity, neither is it surrounded by a common membrane. It consists of several smaller sub-microscopic vesicles. Each gas vesicle is surrounded by a protein membrane that encloses metabolic gases. Air vacuoles store gases and also provide buoyancy and mechanical strength.

Note: Vacuoles are membrane-bound organelles that are found in both prokaryotes and eukaryotes cells. Vacuoles are of 4 types: Food vacuole, Sap vacuole, Gas vacuole, Contractile vacuole.