What is the Difference Between Contractile Vacuole and Food Vacuole

The main difference between contractile vacuole and food vacuole is that contractile vacuole is responsible for osmoregulation and excretion, whereas food vacuole contains digestive enzymes to aid in digestion.

Contractile vacuole and food vacuole are two types of vacuoles with different functions. They are non-cytoplasmic areas separated by a specific membrane.  

Key Areas Covered

1. What is Contractile Vacuole
     – Definition, Structure, Function
2. What is Food Vacuole
     – Definition, Structure, Function
3. Similarities – Contractile Vacuole and Food Vacuole
     – Outline of Common Features
4. Difference Between Contractile Vacuole and Food Vacuole
     – Comparison of Key Differences

Key Terms

Contractile Vacuole, Cryptococcus

What is Contractile Vacuole

The contractile vacuole is a type of vacuole responsible for the osmoregulation ad waste removal of cells. It is a membrane-encased space within the cytoplasm. Osmoregulation is the movement of water and aqueous solutes in and out of the cell. It regulates the water volume and the osmotic pressure of the cell. The contractile vacuole expands to collect water and contracts to expel water. Moreover, contractile vacuoles mainly occur in unicellular organisms that belong to the kingdom Protista. Some multicellular organisms, such as sponges and hydra, also contain contractile vacuoles.

Figure 1: Contractile Vacuole

Furthermore, the stage of water coming into the contractile vacuole is the expansion of the vacuoles, and it occurs by diastole movements. The stage of water expelling out of the cell is the contraction of the vacuole, and it occurs through systole movements.

What is Food Vacuole

The food vacuole is a membrane-enclosed sac having a digestive function. Food vacuoles occur in protozoans such as amoeba and plasmodium. They serve as intracellular stomachs and digest food. It fuses with lysosomes that contain the digestive enzymes of the cell. Finally, the nutrients are released to the cytoplasm. Food vacuoles form by the fusion of phagosomes and pinosomes with lysosomes. In amoeba, the main method of food ingestion is either phagocytosis or pinocytosis. Food particles are trapped by pseudopodia to engulf food particles in the cell in phagocytosis. This forms the phagosome.

Figure 2: Food Vacuole

Moreover, in pinocytosis, the plasma membrane of the cell forms invaginations to trap extracellular fluid, forming vesicles called pinosomes. Both phagosomes and pinosomes move into the center of the cell after their formation. When they fuse with lysosomes, they are called food vacuoles. Therefore, the main function of the food vacuoles is to undergo digestion of the ingested food and release nutrients.  

Similarities Between Contractile Vacuole and Food Vacuole

• Contractile vacuole and food vacuole are two types of vacuoles that occur in cells.
• They are non-cytoplasmic areas surrounded by a specific membrane.
• They have different functions inside the cell.
• Both types of vacuoles occur in protozoans.

Difference Between Contractile Vacuole and Food Vacuole

Definition

Contractile vacuole refers to a vacuole in a unicellular organism that contracts regularly to discharge fluid and especially water from the cell, while food vacuole refers to a membrane-bound cell organelle associated with a digestive function.

Occurrence

Contractile vacuole occurs in freshwater protozoans and metazoans, including sponges and hydras, while food vacuole occurs in unicellular protozoans such as amoeba and plasmodium.

Function

The contractile vacuole is responsible for osmoregulation and excretion, while the food vacuole is responsible for the digestion of food inside the cell.

Importance

The contractile vacuoles excrete waste products to the outside by diastole and systole movement, while food vacuoles aid vacuoles to fuse with lysosomes, containing digestive enzymes.

Conclusion

In brief, the contractile vacuoles and food vacuoles are two types of vacuoles that occur in cells. Contractile vacuoles are a type of vacuoles that occur in freshwater protozoans and metazoans, such as sponges and hydras. They are responsible for the osmoregulation of the cell. Apart from that, contractile vacuoles remove waste products from the cell by diastole and systole movements. In comparison, food vacuoles are a type of vacuoles that occur in unicellular protozoans such as amoeba and plasmodium. They are responsible for digestion. They aid the fusion with lysosomes that contain digestive enzymes for digestion. Therefore, the main difference between contractile vacuoles and food vacuoles is their function.    

References:

1. “Excretion Systems – contractile vacuoles in microorganisms.“ Biology LibreTexts. 
2. “Food vacuole: Definition, location, formation and function.” BYJUS. 

Image Courtesy:

1. “Paramecium contractile vacuoles” By Josh Grosse – Own work (CC-BY SA 3.0) via Commons Wikimedia
2. “Blepharisma diagram” By Deuterostome – Own Work (CC-BY SA 4.0) via Commons Wikimedia