Biology Chapter on Tonicity

Tonicity

• Tonicity is a solution's ability to affect fluid volume and pressure within a cell.
• It depends on solute concentration and permeability.

Isotonic Solution

• An isotonic solution has the same solute concentration as the cytosol.
• Normal saline is an example of an isotonic solution.

Paratonic Solutions

• Paratonic solutions are further categorized as either hypotonic or hypertonic.

Hypotonic Solution

• A hypotonic solution has a lower concentration of non-penetrating solutes than the cytosol.
• Cells placed in a hypotonic solution absorb water, causing them to swell and potentially burst (lyse).

Hypertonic Solution

• A hypertonic solution has a higher concentration of non-penetrating solutes than the cytosol.
• Cells placed in a hypertonic solution lose water, causing them to shrink and shrivel (crenate).

Red Blood Cells in Different Solutions

• If red blood cells are placed in a hypertonic solution, water moves out of the cells, causing them to shrink.
• If red blood cells are placed in a hypotonic solution, water moves into the cells, causing them to swell and potentially burst (hemolysis).

Pharmaceutical Solutions

• Pharmaceutical solutions used in eyes or nose should be isotonic to avoid irritation, especially with large volumes.
• Solutions should also be buffered at the desired pH.

Methods of Adjusting Tonicity

• Methods exist to calculate the amounts of specific substances (like sodium chloride or dextrose)
• This adjustment is to make solutions isotonic.

Cryoscopic Method

• Sodium chloride or another substance may be added to a solution to lower the freezing point to be isotonic to body fluids (-0.52°C).
• Lachrymal fluid serves as a reference point during this method.

Example Calculation (using Sodium Chloride and Apomorphine Hydrochloride)

• Specific calculations use proportions to determine necessary amounts of sodium chloride.
• Additional considerations using 1% solutions are used in these types of calculations.

B - Sodium Chloride Equivalent Method

• A method to determine the quantity of sodium chloride to balance another solution by matching the osmotic effect.
• Sodium chloride equivalents are calculated for comparison for different drugs.

Table of Sodium Chloride Equivalents and Related Data

• Detailed tables providing molecular weights, ions, and equivalents are available to assist in complex calculations of adjusting tonicity.

Example Calculation (using Atropine Sulfate and NaCl)

• Calculations are presented using atropine sulfate and sodium chloride to demonstrate the process of balancing tonicity.

Additional substances (Alternative to NaCl)

• Other substances may also be used, such as boric acid to adjust isotonicity, specifically in ophthalmic solutions.
• This choice is often made for their buffering and anti-infective properties.

Example Calculation (using phenacaine hydrochloride, chlorobutanol, and boric acid)

• Complex calculations demonstrating the process of adjusting ophthalmic prescriptions using different solutions and the equivalent quantities for matching tonicity.

Determining Tonicity of Commercial Products

• Guidance is given to determine if commercial products (like ophthalmic solutions, infusions, etc.) are hypotonic, hypertonic or isotonic.

Explore the concepts of tonicity, including isotonic, hypotonic, and hypertonic solutions. Understand how these solutions affect red blood cells and their behaviors in different environments. This quiz will test your knowledge on fluid dynamics in biological systems.