Food Vacuole

The term vacuole is derived from the word “Vacuum”. The vacuole is a closed sac that is made up of membranes and enzymes. These vacuoles are distributed throughout the cell’s cytoplasm. Vacuoles perform various kinds of functions such as storage of food, disposal of waste, growth, and protection. Food vacuole meaning is as follows: a vacuole which stores food. Food vacuoles are present in smaller sizes in animal cells compared to plant cells.

There 4 different types included in the vacuole: 

1. Sap vacuole

2. Contractile vacuole

3. Food vacuole

4. Air vacuole

What is a Food Vacuole?

So, let us understand food vacuole in a detailed way.

In biological terms, Vacuoles are defined as space in a cell that is fully empty of cytoplasm.  Food Vacuoles are sacs that are enclosed that are membrane-bound. It is present in all fungal cells and plants and some proteins, bacterial cells, and animals. Food Vacuole is present in unicellular protozoans. Plasmodium, Amoeba, etc. are called unicellular protozoans. The space in a cell is fully empty of cytoplasm. Food vacuoles are lined membranes and filled with fluid.

As per the food vacuole definition, it is an enclosed large sac present in the cell. It can also be defined as a specific type of digestive vacuole that can be found in microorganisms. 

Food vacuoles are found in cells of plants, protists, animals and fungi. Food vacuoles are circular portions of the plasma membrane that capture or encircle food particles when they enter the cell. When food particles are entered into the food vacuole the food gets digested and stored as energy. This energy is utilized by the cell. 

Large vacuoles are primarily found in 3 genera of filamentous bacteria of sulfur. They are the Beggiatoa, Thioploca, and Thiomargarita. Food vacuoles also contain sap, water, excretory products, and other materials which are not useful for the cell.

How is Food Vacuole Formed?

• Food vacuoles are formed by the fusion of phagosomes and endosomes to lysosomes. Protozoans like Amoeba take their food by a process called phagocytosis or pinocytosis. 

• In phagocytosis, the surrounding pseudopodia traps the food particles and this food engulfs it inside the cell forming a vesicle called phagosomes. 

• In pinocytosis, the plasma membrane present in the cell forms invagination and traps the droplet of extracellular fluid by forming a vesicle known as pinosomes.

• The phagosomes and endosomes move inside the cell and move towards the center of the cell. These cells fuse with the lysosomes to form the food vacuoles. Then the food is digested and gets diffused into the cytoplasm. The waste material is removed out as the vacuole again merges with the membrane.

• In Paramecium, when the membrane of the discoid vesicle fuses with the cyto pharyngeal membrane, the food vacuoles are formed at the cytopharynx. Then the food is digested and absorbed by the cytoplasm. The waste material is ejected from the cytoproct or anus.

 Types & Functions of Vacuoles

 There are mainly 4 types of Vacuoles. They are as follows:

1. Contractile Vacuoles: These types of vacuoles are mainly found in freshwater. They have a highly collapsible and expandable membrane. They are connected to a few canals having water with or without waste products for the purpose of feeding.

2. Air Vacuole: Air vacuoles are also known as gas vacuoles and pseudo-vacuoles. They are found only in Prokaryotes. It is surrounded by a common membrane. It contains an enormous number of sub-microscopic vesicles. Here, each and every vesicle is surrounded by members of protein and metabolic gases are enclosed in them. The primary functions of air vacuoles are the storage of gases, protection from harmful radiations, buoyancy and mechanical strength.

3. Sap Vacuoles: These are other types of food vacuoles having several transport systems to pass different kinds of substances. In animal and young plant cells, there are numerous small sap vacuoles that are fused to form a single large central vacuole.

4. Food Vacuoles: Food vacuoles are formed as a result of the fusion of lysosomes and phagosomes. They perform different kinds of functions such as ingestion, storage, and excretion of excess water. It is mainly present in unicellular protozoans which includes plasmodium, amoeba, etc.

Functions of Food Vacuole

There are many functions that are performed by food vacuole. The important functions are listed below:

• Food vacuoles contain an enzyme called hydrolyzing enzyme which helps in the digestion of food.

• The cell membrane forms a curve to allow the passage of food particles, when the food is captured completely inside the membrane it pushes into the cell.

• Food vacuole performs the metabolic function in a way that succulent plants open their stomata and take the carbon dioxide from the atmosphere at night. This will be converted then to malic acid and stored in vacuoles until the next day. In the daytime, light energy can be used to convert it to sugar.

• They also perform homeostatic functions in cells of plants that are subjected to wide variations in the environment.

• Molecules can be stored in plant vacuoles and act as a storage organelle for both nutrients and waste products.

• They also perform functions in fungal cells which include the homeostasis of cell pH and storing of amino acids. In animal cells, they tend to perform by helping in exocytosis and endocytosis.

• Food vacuoles allow the organs or germinating plants to grow fastly because of the increase in size.