Question

What would happen to red blood cells in a hypotonic solution?
A. They would shrink due to osmotic water loss.
B. They would rupture due to the influx of water.
C. They would retain their shape due to the cell wall.
D. They would swell but avoid rupturing due to the cell wall.
E. They would pump out excess water with the contractile vacuole.

Answer 1

A cell either shrinks or swells up when a solution of higher concentration leaves or enters into their cell by the process of osmosis. In hypertonic solution cells shrink and they swell up when kept in a hypotonic solution.

Complete answer:
Osmosis is the movement of water from the area of its lower concentration (More solute molecules are present making the solution concentrate) to the area of higher concentration (Less solute molecules are present making the solution dilute). The movement of water in osmosis takes place across a semipermeable membrane.
Tonicity is the ability of an extracellular solution that makes water to move in or out of a cell by osmosis. Three terms are used to describe tonicity –
Hypertonic – When the concentration of the extracellular solution is more than the solution present inside the cell, it leads to the movement of water outside the cells because of which the cell shrinks.
Hypotonic – When the concentration of extracellular solution is less than the solution present inside the cell, it leads to the movement of water towards the inside of the cell because of which the cell swells up and can also burst in some cases.
Isotonic – When the concentration of the extracellular solution is similar to the concentration of solution present inside the cell, no movement of water occurs and the shape of the cell remains as such.
When the red blood cell is placed in a hypotonic solution which has the concentration less than the concentration of solution present in the red blood cell, then the water from the hypotonic solution moves to the inside of the red blood cell causing it to swell up and rupture due to influx of water.

Hence, the correct answer is option (B).

Additional information:
Our body has homeostatic systems that maintain the concentration of extracellular solutions like isotonic solutions for the red blood cells are the best. So our body ensures that the isotonic condition of the solutions is maintained.
Cells of the plant need a hypotonic condition to develop turgor pressure so the cytoplasm of the plant cells have higher concentration compared to the fluid/solution present in the cell. After some time when the turgor pressure is built up then the cell stops the excess influx of water on its own.

Note: Watering the plants is very important as it helps them to maintain a balance between water and solute molecules. If the plants don’t get adequate water then the extracellular fluid becomes hypertonic and the plant cells lose all the water molecules and their turgor pressure is also reduced which results in shrinking of plant cells and can be seen as wilting of leaves.