Key Concepts of Solutions, Concentration, and Cell Membranes

Introduction to Solutions

• Definition: A solution consists of a solute dissolved in a liquid (solvent).
  • Solute: Substance dissolved (e.g., salt, sugar).
  • Solvent: Liquid in which the solute is dissolved.
• Types of Solvents: Commonly water (aqueous solution), but can be alcohol, oil, etc.

Understanding Concentration

• Definition: The amount of solute in a specific volume of liquid.
• Example: More solute means higher concentration.
• Percent Concentration: Used to express how concentrated a solution is.
  • Example: 5% means 5 grams of solute per 100 milliliters of solvent.

Common Medical Solutions

• 5% Glucose (Dextrose): Common in hospitals.
• 0.9% Saline Solution: Known as normal saline, second most common.

Diffusion

• Definition: Spontaneous movement of solute from higher to lower concentration.
• Examples:
  • Blue dye in water spreads until evenly distributed.
  • Perfume spreads from high concentration in the bottle to the air.

Cell Membranes

• Structure: Composed of a double layer (bilayer) of phospholipids.
  • Phospholipids: Molecules with hydrophilic (water-attracting) heads and hydrophobic (water-repellent) tails.
  • Function: Separate cell interior from external environment.

Factors Affecting Diffusion

1. Temperature: Higher temperatures increase diffusion rate.
2. Concentration Gradient: Greater differences speed up diffusion.
3. Molecule Size: Smaller molecules diffuse faster.
4. Solubility: Determines if and how a molecule can diffuse through the membrane.

Osmosis

• Definition: Diffusion of water across a cell membrane.
• Importance: Maintains cell structure and function by regulating water flow.

Tonicity

• Isotonic Solutions: Equal concentration inside and outside the cell; no net water movement.
• Hypotonic Solutions: Lower solute concentration outside; water flows into cell, possibly causing it to burst.
• Hypertonic Solutions: Higher solute concentration outside; water flows out, causing cell to shrink.

Practical Implications

• Understanding these concepts helps in comprehending medical conditions and treatments, especially in hospital settings.
• Knowledge of solutions, diffusion, and osmosis is crucial for future courses in anatomy, physiology, and pharmacology.