An isotonic solution has the same solute concentration as the inside of a cell, maintaining equilibrium and preventing net water movement. In this state, osmosis does not cause water to enter or exit the cell, preserving cell size and function. Isotonic solutions are crucial in medical treatments, such as intravenous fluids, to ensure cells remain stable. Understanding isotonic solutions helps grasp the fundamental concepts of osmosis and cell membrane dynamics.
An isotonic solution is a solution with the same solute concentration as the cell’s interior, resulting in no net water movement across the cell membrane through osmosis. This balance ensures cells maintain their normal shape and function without swelling or shrinking.
Isotonic solutions have a solute concentration that matches the osmolarity of body fluids, typically around 290 mOsm/L. Here are common isotonic solutions and their concentrations:
1. Intravenous (IV) Fluids
2. Ophthalmic Solutions
3. Injectable Solutions
4. Oral Rehydration Solutions (ORS)
| Feature | Isotonic Solution | Hypertonic Solution |
|---|---|---|
| Solute Concentration | Equal to the inside of the cell | Higher than the inside of the cell |
| Osmolarity | ~290 mOsm/L | Greater than 290 mOsm/L |
| Effect on Cells | No net water movement; cells retain normal shape | Water leaves the cell; cells shrink (crenation) |
| Medical Use | Hydration, medication dilution, maintaining electrolyte balance | Reducing cerebral edema, treating hyponatremia |
| Examples | Normal Saline (0.9% NaCl), Ringer’s Lactate | 3% NaCl solution, 5% Dextrose in Normal Saline |
| Function in the Body | Maintains fluid balance without altering cell volume | Draws water out of cells, reducing swelling |
They maintain cell size and function by preventing net water movement.
Normal Saline (0.9% NaCl) is a common example.
Osmosis is the movement of water across a semipermeable membrane from low to high solute concentration.
It prevents cells from swelling or shrinking.
Approximately 290 mOsm/L.
Yes, they are used to rehydrate patients.
An isotonic solution with electrolytes used for fluid resuscitation.
Yes, but it becomes hypotonic after dextrose metabolism.
They are used for intravenous hydration and medication dilution.
It means the solution contains 0.9 grams of sodium chloride per 100 milliliters of water.
What is the definition of an isotonic solution?
A solution with a higher concentration of solutes than the cell
A solution with the same concentration of solutes as the cell
A solution with a lower concentration of solutes than the cell
A solution with no solutes
When a cell is placed in an isotonic solution, what happens to the cell?
It swells
It shrinks
It remains the same size
It bursts
In medical practice, why are isotonic solutions used in IV fluids?
To cause cells to shrink
To prevent changes in cell size
To cause cells to swell
To remove solutes from the bloodstream
Which of the following is an example of an isotonic solution used in healthcare?
10% saline solution
5% glucose solution
0.9% saline solution
Distilled water
What happens to the rate of water movement in a cell placed in an isotonic solution?
Water moves into the cell faster than it moves out
Water moves out of the cell faster than it moves in
Water moves equally in and out of the cell
Water does not move at all
How does the osmotic pressure compare between an isotonic solution and a cell?
The isotonic solution has higher osmotic pressure
The isotonic solution has lower osmotic pressure
The isotonic solution has the same osmotic pressure
The isotonic solution has no osmotic pressure
In which of the following situations would you not use an isotonic solution?
Treating dehydration
Correcting cell shrinkage
Maintaining fluid balance during surgery
Hydrating cells without altering their size
Why do animal cells remain stable in an isotonic solution?
The concentration of solutes inside and outside the cell is the same
Water moves out of the cell
Water moves into the cell
Solutes move into the cell faster than out
What could happen to red blood cells if placed in a solution that is not isotonic?
They could remain unchanged
They could shrink or swell, depending on the solution
They could become isotonic
They could lose solutes
In plant cells, what effect does an isotonic solution have on the turgor pressure?
Increases turgor pressure
Decreases turgor pressure
No effect on turgor pressure
Causes plasmolysis