Question

In amoeba, osmoregulation is carried out by
a. Food vacuole
b. Plasma membrane
c. Contractile vacuole
d. Both B and C

Answer 1

Hint: Amoeba is a unicellular prokaryotic organism capable of changing its shape. It moves with the help of contracting and retracting pseudopodia. Being unicellular and prokaryotic, there are very few organelles enclosed within the cell membrane.

Complete answer:
Amoeba is a unicellular organism belonging to the class of Sarcodina that possesses pseudopodia. The word pseudopodia means false foot. Therefore, Amoeba moves with the help of false feet by the process of contracting and retracting. This movement is known as the Amoeboid movement. The contractile vacuoles present in them are responsible for excretion, osmoregulation, and circulation.

> Option A is incorrect: Food vacuole is the storage unit of amoeba. It is an organelle that only emerges after the amoeba has engulfed its prey and digestion is required. This vacuole contains enzymes for the digestion of the food.

> Option B is correct: Amoeba has a thin membrane composed of proteins and lipids called the plasma membrane. It is responsible for allowing substances to enter the cell and protect the constituents of the cell. When the vacuole is full, the cell can burst. To control the excess amount of water the cell membrane throws out the extra water by exosmosis.

> Option C is correct: The contractile vacuole is the one that contains solutes and solvents dissolved. The concentration of solutes in amoeba is always higher than the surrounding. So, the process of endosmosis maintains the water balance. But when the cell has excess water it gets expelled with the help of the cell membrane.

Since both the plasma membrane and the contractile vacuole is responsible for osmoregulation in amoeba.
Hence, the correct answer is option (D).

Note: Marine amoeba does not contain contractile vacuoles. This is because the concentration of solutes within the cells is in balance with the surrounding environment. Their tonicity is the same, so they do not require osmoregulation.