Food Vacuole: Structure, Type and Functions

A membrane-enclosed sac is termed a Food Vacuole. Food Vacuole is present in unicellular protozoans such as plasmodium, amoeba, etc. In biology, a vacuole is termed as a space in a cell that is fully empty of cytoplasm. It is a lined membrane filled with fluid. Vacuoles are usually cytoplasmic organs. They perform functions such as ingestion, storage, digestion, expulsion, and excretion of excess water. In-plant cells large central vacuoles are found. It enables them to attain a large size without accumulating bulk, which makes metabolism difficult. In this article, we will learn in-depth about Food Vacuole. 

Read More: Difference Between Cytoplasm and Protoplasm

Definition And Meaning Of Food Vacuoles

Food Vacuoles are an organelle that is membrane-bound and present in all fungal cells and plants and some proteins, bacterial cells, and animals. Food Vacuole is present in unicellular protozoans such as plasmodium, amoeba, etc. The vacuole is bound by a single membrane.

Vacuoles are those non-cytoplasmic areas that are found inside the cytoplasm and separated by the specific membranes from the latter. These are believed to be formed because of the pinching and expansion of the ER. A membrane-enclosed sac is termed a Food Vacuole. It has one important function which is a Digestive Function. space in a cell that is fully empty of cytoplasm. It is a lined membrane and it’s filled with fluid. 

Large vacuoles are even found in 3 genera of filamentous bacteria of sulfur, the Beggiatoa, Thioploca, and Thiomargarita. Several vacuoles in a single cell may be found. Every vacuole is segregated from the cytoplasm with a single unit membrane which is called the Tonoplast.

Food vacuoles contain sap, water, excretory products, and other materials which are not useful for the cell.

Structure Of Food Vacuole

• Food Vacuoles have no specific or basic size or shape. Food Vacuole’s structure varies according to the need and requirements of the cells.
• In the actively dividing and immature plant cells these vacuoles are quite small. They arise priorly in young dividing cells, generally by progressive fusion of vesicles which are derived from Golgi apparatus.
• The vacuole is surrounded by a cell membrane which is called a vacuolar or tonoplast membrane which is filled with the sap of the cell.
• Every vacuole is segregated from the cytoplasm with a single unit membrane which is called the Tonoplast. Tonoplast is a cytoplasmic membrane. It separates the vacuolar contents of the cytoplasm from the cells. 
• These vacuoles are functionally and structurally linked to lysosomes in animal cells and they may contain a range of hydrolytic enzymes.
• The plant vacuoles' pH may be as high as 10 because of large quantities of alkaline particles and substances or low to 3 because of accumulation of acids.

Read More: Human Digestive System

Types Of Vacuoles

1. Sap Vacuoles

These are those types of vacuoles that have several transport systems to pass the different substances. Numerous small sap vacuoles are there in animal and young plant cells. In some mature plants, small vacuoles fuse to form a single large central vacuole. It occupies around 90% of the cell. The central vacuole spreads the cytoplasm of a thin peripheral layer. It facilitates rapid exchange and the surrounding environment.

2. Contractile Vacuoles

These are those kinds of vacuoles that occur in some algae and protist cells which are found mostly in freshwater. These are those types of contractile vacuoles which have a highly collapsible and expandable membrane. These are also connected to a few canals which are for feeding. These canals have water with or without waste products from the cytoplasm surrounding them. It pours the same into the vacuole of the contractile.

3. Food Vacuoles

These kinds of vacuoles are present in protozoan protists cells, in several lower animals, and phagocytes of higher animals. These are formed by the fusion of a lysosome and a phagosome. It has digestive enzymes with which the nutrients are digested. Then these digested materials pass out into the cytoplasm’s surroundings.

4. Air Vacuoles (Gas Vacuoles, Pseudo-Vacuoles)

These kinds of vacuoles are found only in Prokaryotes. This vacuole is not just a single entity, and it is as such surrounded by a common membrane. It has numerous numbers of sub-microscopic vesicles. In this, every vesicle is the one that is surrounded by a membrane of protein and encloses metabolic gases. It does not only store gases but also provides mechanical strength, buoyancy, and protection from harmful radiations.

Function And Structure Of Vacuoles

Functions Of Food Vacuoles

Vacuoles have numerous functions. Some of them are-

• They can store various types of molecules. It even acts as a storage organelle for both waste products and nutrients.
• Some products which are stored by vacuoles have a metabolic function.
• They can sequester substances that are harmful to cells of plants, only if they are present in the cytoplasm in bulk.
• They have a vital homeostatic function in cells of plants and these are subjected to various variations in the environment.
• These vacuoles maintain turgor pressure at constant levels due to the large changes in tonicity of fluids in the immediate nature by interchanging somatic pressure of vacuole and cytoplasm. A part of which is resynthesis of polymers and controlled breakdown such as polyphosphate in the vacuole, by altering.
• Due to the increase in size, they allow the organs or germinating plants to grow quickly and mostly water.
• Stored proteins in seeds are needed for germination and these are kept in ‘Protein Bodies’, and these are modifying vacuoles.

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Things To Remember Based on Food Vacuole

• A membrane-enclosed sac is termed a Food Vacuole. It has one important function which is a Digestive Function.
•  Food Vacuole is present in unicellular protozoans such as plasmodium, amoeba, etc. 
• In biology, a vacuole is termed as a space in a cell that is fully empty of cytoplasm. 
• It is a lined membrane filled with fluid. 
• Vacuoles are usually cytoplasmic organs, especially found in Protozoa.
• There are 4 types of food vacuoles.
  • Sap Vacuole
  • Contractile Vacuole
  • Air Vacuole
  • Food Vacuole
•  It even acts as a storage organelle for both waste products and nutrients.
• Food Vacuole’s structure varies according to the need and requirements of the cells.