Biophysics Fundamentals: Solutions, Diffusion, and Osmosis

Biophysics Fundamentals

Biophysics is a branch of biology that studies the physical phenomena produced inside the cellular plasma.

1. Systems of Dispersions

A dispersion is a mixture of two substances in which one completely surrounds the other without settling. It consists of two phases:

• Dispersed phase: The solute.
• Dispersing phase: The solvent.

Classification of Dispersions

Dispersions are classified into three groups, including suspensions and emulsions.

Molecular Solutions

A solution or molecular dispersion is a mixture where both phases are closely linked to form a homogeneous, transparent substance.

Concentration of Solutions

Solutions are categorized by their solute concentration:

• Saturated: Contains the maximum amount of solute possible to dissolve.
• Supersaturated: Contains more solute than the solvent can normally hold.
• Concentrated: Solutions close to saturation.
• Diluted: Contains a very small amount of solute.

Diffusion

Diffusion is the flow or movement of solute within a dispersant. In liquids, this forms a homogeneous mixture.

Importance of Diffusion

This phenomenon occurs constantly in secretory cells to maintain a constant composition throughout the body. Diffusion is regulated by three types of membranes:

• Permeable: Allows the passage of both phases.
• Impermeable: Does not allow the passage of substances.
• Semipermeable: Allows only the passage of the solvent.

Osmosis

Osmosis is a physical phenomenon similar to diffusion, involving the passage of a solvent through a semipermeable membrane, which acts as a sieve.

Osmotic Pressure

Osmotic pressure is the force exerted by dissolved molecules based on the concentration of the solutions.

Classes of Solutions by Osmotic Pressure

• Isotonic: Both solutions have the same concentration and identical osmotic pressure.
• Hypertonic or Hypotonic: Solutions have different degrees of concentration and osmotic pressure.

Biological Importance of Osmosis

Osmosis maintains the turgor of plant cells through endosmosis (internal pressure) and provides water via exosmosis (external pressure) to support vital life processes.