What happens if cells are placed in solutions with the same or different concentrations than the cell?

The Biology Project > Cell Biology> Cell Membranes> Problem Set

Problem 4: Osmosis

Tutorial to help answer the question

A sample of cells is placed in a salt solution. The cells shrink and the membrane is distorted. Relative to the cell, the solution is probably:

A.	isotonic.
B.	hypotonic.
C.	osmotic.
D.	hypertonic.

Tutorial

Cells in aqueous solutions

The figures show what can happen when animal or plant cells are placed in an aqueous solution. Water can move across membranes, but polar solutes dissolved in water cannot. The net movement of water (osmosis) is in the direction of increased solute concentrations. An easy way to visualize this rule is simply that the net water movement is from an area of high water concentration (little dissolved solute) to an area of low water concentration (high levels of solute).

The Biology Project > Cell Biology> Cell Membranes> Problem Set

http://www.biology.arizona.edu
All contents copyright © 2002-04. All rights reserved.

Skill:

•  Estimation of osmolarity in tissues by bathing samples in hypotonic and hypertonic solutions

    
Osmolarity is a measure of solute concentration, as defined by the number of osmoles of a solute per litre of solution (osmol/L)

Solutions may be loosely categorised as hypertonic, hypotonic or isotonic according to their relative osmolarity

• Solutions with a relatively higher osmolarity are categorised as hypertonic (high solute concentration ⇒ gains water)
• Solutions with a relatively lower osmolarity are categorised as hypotonic (low solute concentration ⇒ loses water)
• Solutions that have the same osmolarity are categorised as isotonic (same solute concentration ⇒ no net water flow)

Osmotic Movement between Solutions:  Hypertonic (left) and Hypotonic (right)

Estimating Osmolarity

The osmolarity of a tissue may be interpolated by bathing the sample in solutions with known osmolarities

• The tissue will lose water when placed in hypertonic solutions and gain water when placed in hypotonic solutions
• Water loss or gain may be determined by weighing the sample before and after bathing in solution
• Tissue osmolarity may be inferred by identifying the concentration of solution at which there is no weight change (i.e. isotonic)

Application:

•  Tissues or organs to be used in medical procedures must be bathed in a solution with the same osmolarity 

   as the cytoplasm to prevent osmosis

    
Tissues or organs to be used in medical procedures must be kept in solution to prevent cellular dessication

This solution must share the same osmolarity as the tissue / organ (i.e. isotonic) in order to prevent osmosis from occurring

Uncontrolled osmosis will have negative effects with regards to cell viability:

• In hypertonic solutions, water will leave the cell causing it to shrivel (crenation)
• In hypotonic solutions, water will enter the cell causing it to swell and potentially burst (lysis)

In plant tissues, the effects of uncontrolled osmosis are moderated by the presence of an inflexible cell wall

• In hypertonic solutions, the cytoplasm will shrink (plasmolysis) but the cell wall will maintain a structured shape
• In hypotonic solutions, the cytoplasm will expand but be unable to rupture within the constraints of the cell wall (turgor)

Summary of the Effects of Solute Concentrations on Cells

What will happen if cells are placed in solutions with concentrations the same as or different from those of the cell fluids?

What will happen to the cell if same or equal concentration?

What happens when a cell is placed in a solution with a solute concentration equal to the inside of the cell?

When the concentration of a solution is the same as that of the cell the solution is said to be?