Question

Tonoplast is
a. Permeable membrane
b. Semi-permeable membrane
c. Impermeable membrane
d. Selectively permeable membrane

Answer 1

Hint: Cells are of two main types- animal cells and plant cells. Plant cells have many vacuoles which fuse to form central vacuole. Vacuole occupies major space in the plant cell. Vacuole maintains turgor pressure.

Complete answer:
Cell is the structural and functional unit of life. The two main types of cells- plant cell and animal cell have certain differences. For example- a plant cell has a cell wall whereas a cell wall is absent in an animal cell. Another difference is that a plant cell contains more vacuoles than animal cells.

Vacuoles are large vesicles derived from the endoplasmic reticulum and Golgi body. Plant cells have many vacuoles which fuse to form central vacuole. Vacuole occupies major space in the plant cell. Vacuole maintains turgor pressure. It is able to do because the vacuole is surrounded by a membrane called the tonoplast. It is a single layered membrane. The vacuole is filled with cell sap. The concentration of cell sap inside vacuole is higher than cytosol.

Vacuole stores food and excretory products. The main difference between semi permeable and selectively permeable is that semi permeable allows solvent molecules and solute molecules to easily pass through it whereas selectively permeable membrane chooses the substances to allow them to pass through. The tonoplast does so. The tonoplast selects substances that it would allow to pass through. It takes up molecules and ions against concentration gradient which results in higher concentration inside vacuole than cytosol. Tonoplast contributes to flexibility of cell. This property is very prominent in case of certain protists like amoeba. Amoeba has contractile vacuole.

Hence, The correct answer is option (D).

Note: Vacuoles are present in both plant and animal cells. Plant cell has a large central vacuole whereas an animal cell has fewer vacuoles. Vacuoles are of different types and these types have different functions.