Which one of the following cell organelles may play a role in expellin

Which one of the following cell organelles may play a role in expelling excess water and wastes in case of unicellular organisms ?

Lysosome
Vacuole
Golgi body
Endoplasmic reticulum
This question was previously asked in
UPSC NDA-2 – 2020
In many freshwater unicellular organisms like *Paramecium* or *Amoeba*, contractile vacuoles are specialized organelles that collect excess water that enters the cell by osmosis and periodically expel it out. This process is crucial for osmoregulation, preventing the cell from bursting in a hypotonic environment. Wastes can also be expelled via this mechanism or through other means like diffusion or exocytosis.
– Vacuoles in unicellular organisms can include contractile vacuoles, which are vital for maintaining osmotic balance by expelling excess water.
– Lysosomes are involved in intracellular digestion.
– Golgi body (or Golgi apparatus) is involved in modifying, sorting, and packaging proteins and lipids for secretion or delivery to other organelles.
– Endoplasmic reticulum is involved in protein and lipid synthesis.
Contractile vacuoles are found mainly in protists living in freshwater habitats. Their rate of pulsation is regulated by the osmotic potential of the surrounding medium; they pump faster in more dilute environments. While primarily for water expulsion, they also contribute to the removal of some metabolic wastes.
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