Question

If the solute concentration is higher in the external solution, then the solution is called
(A)Hypotonic
(B)Isotonic
(C)Hypertonic
(D)None of the above

Answer 1

Hint: Hypertonic and hypotonic are measures of tonicity of a solution. By tonicity, we mean the effective osmotic pressure gradient, the water potential of two solutions which are separated by a semipermeable membrane.

Complete answer:
When the solute concentration is higher in the external solution then the solution is known as a Hypertonic solution. It is a measure of the tonicity of the two solution systems. Here the outside of a cell has a greater concentration of solutes than the cytosol inside the cell membrane. In the hypertonic solution, the water flows out of the cell by osmosis in order to balance the Concentration on either side of the membrane. In this case, the cytosol is said to be hypotonic.

Additional information:
Opposite to a hypertonic solution, a Hypotonic one had a lower concentration than another solution. In the above case, the cytosol is hypotonic and the external space of the cell is in hypertonic condition. If we emerge the cell in a hypotonic solution, the water will diffuse inside the cell to maintain the Concentration on either side and that will result in the cell becoming turgid or bloated.
There are also isotonic solutions where the Concentration on each side of the membrane is the same so there occurs no shrinking or bloating of the cell. However, water freely diffuses in both directions.
So, the correct answer is option (c) "Hypertonic".

Note: In the case of the plant cells, when the cell is in hypertonic solution only their plasma membrane pulls away from the rigid cell wall but the cell wall remains attached on points known as plasmodesmata. In the case of a hypotonic solution, the central vacuole takes on extra water and pushes the cell membrane towards the cell wall but due to the rigidity of the wall, the cell remains intact.