Untitled

Solubilisation

Definition

  • Solubilisation is defined as the ability to dissolve substances that are insoluble in a pure dispersion medium.

Key Concepts

  • Polárně-nepolární látka (Co-surfactant): Refers to polar and non-polar substances in the context of surfactants that aid in solubilisation.

Illustrations of Solubilisation

  • Illustration 11.12: Depicts solubilisation processes with various types of micelles:

    • (a), (b), (c): Small micelles

    • (d): Lamellar micelles

    • (e): Non-ionic micelles

Micelle Formation

Components of Micelles

  • Iontová hlava (Ionic "Head"): Contains carboxylate (–COO) groups that are hydrophilic.

  • Uhlohydíkový "ocas" (Hydrocarbon "Tail"): The hydrophobic part of surfactants or molecules that are non-polar in nature.

Behavior in Water

  • Micelles form in aqueous solutions where the polar heads face outward and the hydrophobic tails face inward, creating a spherical structure.

Micellar Colloids

Definition and Characteristics

  • Micelles are colloidal structures formed by association of surfactant molecules in a specific concentration.

Micelle Types and Related Terms

  • Critical Micellar Concentration (CMC, KMK): The concentration above which micelles form.

  • Hartleyova micela: Refers to a specific type of cylindrical micelle contained within the system, identified by certain structural properties.

  • Laminární McBainova micela: This refers to a layered structure in micelle formation with specific interaction dynamics.

  • Hydrophilic and Hydrophobic traits: The micelles have regions that interact well with water and regions that avoid water, a defining trait of surfactants.

Physical Properties Related to Micelles

  • Osmotic pressure, viscosity, turbidity, surface tension, and molar conductivity all relate to the concentration and type of micelles formed in a given environment.

Formation and Function of Micelles

Process Steps

  1. Ionization of Cholic Acid: The typical bile acid cholic acid ionizes to form a corresponding bile salt.

  2. Association with Triacylglycerol: The hydrophobic surface of bile salts associates with triacylglycerol leading to aggregation into micelles.

  3. Interaction with Pancreatic Lipase/Colipase: The hydrophilic surface of bile salts allows for interaction with pancreatic lipase, facilitating the breakdown of triacylglycerols into free fatty acids which then form smaller micelles that can be absorbed.

Micelle Composition

  • Typical components include bile salts, triacylglycerols, and free fatty acids.

Structure of Lipoproteins

Composition

  • Core: Contains triacylglycerols and cholesteryl esters.

  • Phospholipids and Cholesterol: Contributes to the structural integrity of lipoproteins.

  • Apolipoproteins: These are protein components that associate with lipoproteins, playing critical roles in metabolism.

Structural Characteristics

  • Lipoproteins consist of hydrophilic groups that orient outward in an aqueous environment, and hydrophobic groups that orient inward, encapsulating the hydrophobic core substances.

Osmotic Phenomena

Definition of Osmosis

  • Osmosis is described as the movement of solvent from a region of lower solute concentration to a region of higher solute concentration through a semipermeable membrane.

Key Terms

  • Semipermeable Membrane: A barrier that allows certain substances to pass while blocking others.

  • Equilibrium: Achieved when solute concentrations are equal on both sides of the membrane.

Osmotic Pressure

  • Defined mathematically by the equation: extOsmoticpressure(extπ)=nimesRimesText{Osmotic pressure }( ext{π}) = n imes R imes T

    • Where:

    • nn: Van 't Hoff factor

    • RR: Ideal gas constant

    • TT: Temperature in Kelvin

Colligative Properties

  • Colligative properties depend solely on the number of solute particles in solution, regardless of their identity.

Raoult's Law

  • Asserts that vapor pressure over a solution is a function of the mole fraction of the solvent. It describes how solute addition reduces vapor pressure.

Isotonic Coefficient Equation

  • Given as i=1+extα(n−1)i = 1 + ext{α} (n-1) where:

    • extαext{α} represents the degree of ionization,

    • nn is the number of ions produced from a compound.

Osmotic Pressure in Living Organisms

Types of Solutions

  • Hypotonic Solutions: Solvent penetrates the cell leading to plasmolysis, which causes dilution and risks cell rupture.

  • Hypertonic Solutions: Water is pulled out of the cell leading to thickened contents, referred to as plasmolysis.

  • Isotonic Solutions: Equal pressure within the solution and the cell, commonly used in medical infusions to maintain cellular integrity.

Concentration Gradients in Cells

Membrane Dynamics

  • The cytosol has a higher concentration of potassium ions (K+K^+) and impermeable anions compared to extracellular fluids, creating a concentration gradient.

  • Diffusion of potassium ions out of the cell results in the establishment of a membrane potential, which increases until equilibrium is reached.

Sodium-Potassium Pump

  • A small amount of sodium ions (Na+Na^+) leak into the cell, but excess Na+Na^+ is actively transported out via the Na+/K+ pump, crucial for maintaining ionic balance and membrane potential.

Membrane Potential

  • The membrane potential changes as ion concentrations shift, influencing cellular functions and communications.

Osmotic Pressure in Internal Compartment Management

Osmotic Control Mechanisms

  • The control of osmotic pressure is essential for maintaining homeostasis in bodily fluids.

  • Measurements of osmolality can guide clinical practices in evaluating fluid states in patients.

Parameters Affecting Osmotic Pressure

  • The collective osmotic pressure in blood comprises hydrostatic pressures affected by distance from the heart and colloid osmotic pressures due to plasma proteins.

Hydrostatic Pressure Relations

  • Expressed as follows:

    • extPH=extΠ0ext{PH} = ext{Π}_0: No net water movement; equilibrium.

    • extPH<extΠ0ext{PH} < ext{Π}_0: Water moves into the interstitial spaces.

    • Example values given:

    • extΠ0=3.73extkPaext{Π}_0 = 3.73 ext{ kPa},

    • extPHext{PH} at arterial and venous pressures.

Osmolarity Calculations

Definitions

  • Osmolarity: The number of osmotically active particles per liter of solution. Examples:

    • 1 M glucose corresponds to 1 Osm,

    • 1 M NaCl corresponds to 2 Osm.

Isotonic Solutions

  • An isotonic solution for blood cells has an osmolarity of about 310 mOsm, which equates to:

    • 310 mM glucose or 155 mM NaCl.

Osmolality vs Concentration

  • Terminology:

    • Osmolarity: measured in [extosmolextdm−3][ ext{osmol} ext{ dm}^{-3}],

    • Osmolality: measured in [extosmolextkg−1][ ext{osmol} ext{ kg}^{-1}].

    • 1 osmol corresponds to 1 mole of osmotically active substance.

Plasma Osmolality

Concentrations of Active Particles

  • Typical values of osmolality in plasma are around 290 ± 5–10 mmol/kg H₂O.

  • Contribution breakdown of osmotically active particles includes:

    • NaCl, H₂O, proteins, etc.

Osmolality Calculations

Calculation Methods

  • Osmolality can be derived using traditional formulas:

  • extOsm=2imesPextNa+PextGlucose+PextUreaext[mmol/kg]ext{Osm} = 2 imes P_{ ext{Na}} + P_{ ext{Glucose}} + P_{ ext{Urea}} ext{ [mmol/kg]}

  • Additional contributions may include potassium and chlorides as needed.

Osmolal Gap

  • Defined as the difference between calculated and measured osmolality. An increase in the gap may indicate the presence of unmeasured solutes.