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Difficulty: EasyKingdom Protista: Protozoa and Unicellular Algae

Which organelle is primarily responsible for osmoregulation and removing excess water in *Amoeba proteus*?

  1. Contractile vacuoleAnswer
  2. B
    Food vacuole
  3. C
    Chloroplast
  4. D
    Cell wall

Answer

The contractile vacuole is the organelle responsible for osmoregulation in *Amoeba proteus*.
In freshwater protozoa such as *Amoeba*, the cytoplasm is hypertonic relative to the surrounding water. Consequently, water continuously diffuses into the cell through osmosis. The contractile vacuole acts as an osmoregulatory structure that accumulates this excess fluid and regularly discharges it to the exterior environment, preventing hydrostatic swelling and cell rupture.

Step-by-Step Solution

1
Identify the physiological challenge faced by freshwater protozoans like *Amoeba proteus*.
Freshwater is hypotonic to the cytoplasm of *Amoeba*, causing water to constantly enter the cell by osmosis.
Understanding the osmotic gradient explains why a specialized water-expelling structure is necessary to prevent lysis.
2
Select the organelle dedicated to collecting and expelling this excess water.
The contractile vacuole expands as it fills with water and periodically fuses with the cell membrane to pump water out.
This process maintains the organism's water and solute balance (osmoregulation).

Key Concept

Osmoregulation in Protozoa via Contractile Vacuole
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Topics

Kingdom Protista: Protozoa and Unicellular Algae

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