Food vacuole is a membrane-enclosed sac, which has a digestive function. It is present in unicellular protozoans such as amoeba, plasmodium, etc.
They work as an intracellular stomach, digesting the ingested food. It contains digestive enzymes, which break down the food and then it is released into the cytoplasm for utilization.
Food Vacuole Formation
Food vacuoles are formed by the fusion of phagosomes and pinosomes to lysosomes.
Protozoans like Amoeba take their food by phagocytosis or pinocytosis. In phagocytosis, food particles are trapped by surrounding pseudopodia and they engulf it inside the cell forming a vesicle called phagosomes. In pinocytosis, the plasma membrane of the cell forms invagination and traps the droplet of extracellular fluid by forming a vesicle known as pinosomes.
Phagosomes and pinosomes pinch off inside the cell and move towards the centre of the cell. They fuse with lysosomes to form food vacuoles. Here food is digested and diffuses to cytoplasm. The waste material is expelled out as the vacuole again merges with the membrane.
In Paramecium, food vacuoles are formed at cytopharynx, when membrane of discoid vesicle fuses with cytopharyngeal membrane. The food is digested and absorbed by the cytoplasm. The waste material is ejected from the cytoproct or anus.
Food Vacuole Function
Food vacuoles contain hydrolysing enzymes as they are formed by fusion with lysosomes. The food is digested by hydrolysing enzymes. The amino acids, sugar, etc. which are produced after breakdown are diffused into cytosol. Thus, ingested food is digested and absorbed.
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