Solution Colloid Crystalloid Dialysis (Biophysics & Biomolecules- item 2) Biochemistry
Summary
The video explains Item 2 of the Biophysics and Biomolecules card, focusing on Solutions, Crystalloids, Colloids, Dialysis, and Isotopes. It begins by defining solutions, solvent, solute, and differentiating between homogeneous and heterogeneous mixtures. The discussion then delves into colligative properties (vapor pressure lowering, boiling point elevation, freezing point depression, osmotic pressure) and categorizes solutions into crystalloids and colloids based on particle size and membrane permeability. The differences between crystalloids, colloids, and suspensions are detailed, along with properties of colloids like Brownian movement and Tyndall phenomenon. The video also covers colloidal osmotic pressure's role in fluid balance, dialysis as a separation technique, and osmolality, comparing plasma osmolality with normal saline and explaining tonicity's effect on red blood cells and body fluids.
Key Insights
Colligative properties of solutions depend solely on the number of solute particles, not their identity.
The video explains that colligative properties, such as vapor pressure lowering, boiling point elevation, freezing point depression, and osmotic pressure, are physical properties of a solution that are determined only by the quantity of solute particles present, irrespective of what type of solute it is. For instance, whether potassium chloride or sodium chloride is added as a solute, the effect on these properties depends on the number of particles each dissociates into, not the chemical identity of KCl or NaCl.
Colloidal osmotic pressure (COP) is crucial for maintaining fluid balance in the body.
Colloidal osmotic pressure, exerted by colloidal particles like plasma proteins, helps retain water within blood vessels. A decrease in COP, often due to a low concentration of plasma proteins, leads to water shifting from blood vessels into the interstitial space, potentially causing edema. Conversely, an increase in COP would pull more water into the blood vessels, leading to blood vessel expansion and dehydration of cells.
Dialysis is a key technique for separating colloids from crystalloids, particularly in kidney failure patients.
Dialysis is a physical process used to separate colloids from crystalloids using a semi-permeable membrane. In the context of renal failure, dialysis is essential for removing waste products (crystalloids) from the blood, such as potassium and ammonia, while retaining vital components like blood cells and plasma proteins (colloids) that cannot pass through the membrane. The process involves diffusion driven by concentration gradients, with the dialysis fluid being exchanged to ensure continuous removal of waste.
Tonicity describes a solution's osmotic activity relative to a cell, influencing water movement and cell volume.
Tonicity refers to the concentration of solutes in a solution that can exert osmotic pressure, specifically regarding non-diffusible ions. When red blood cells are placed in hypertonic solutions, water leaves the cells, causing them to shrink. In hypotonic solutions, water enters the cells, causing them to swell. In isotonic solutions, there is no net movement of water, and the cell volume remains stable. This principle is also applied to the administration of intravenous fluids, determining whether they are hypertonic, hypotonic, or isotonic to plasma.
Sections
Introduction to Solutions
A solution is a homogeneous mixture of two or more substances.
A solution is defined as a homogeneous mixture where substances are uniformly distributed. Homogeneous implies the same composition throughout, contrasting with heterogeneous mixtures where compositions vary.
Solvent is the dissolving medium, and solute is the substance dissolved.
In a solution, the solvent (দ্রাবক) is the component that dissolves the other substance, while the solute (দ্রব) is the substance that gets dissolved.
Solutions can be true (homogeneous) or false/pseudo (heterogeneous).
True solutions are homogeneous mixtures. Heterogeneous solutions, also called false or pseudo solutions, involve aggregates of molecules that do not distribute uniformly, such as blood or a solution of protein in water.
Concentration and Colligative Properties
Concentration refers to the amount of solute in a given amount of solvent or solution.
Concentration, or ঘনমাত্রা, quantifies the amount of solute present in a solution. Common units include molarity, normality, molality, and ppm, which were studied at the intermediate level.
Colligative properties depend only on the number of solute particles, not their identity.
Colligative properties are physical characteristics of a solution that are determined solely by the number of solute particles, not the chemical nature of the solute. Examples include vapor pressure lowering, boiling point elevation, freezing point depression, and osmotic pressure.
Four main colligative properties are vapor pressure lowering, boiling point elevation, freezing point depression, and osmotic pressure.
The four key colligative properties are: 1. Vapor Pressure Lowering: Solutes reduce the vapor pressure of the solvent. 2. Boiling Point Elevation: Solutions boil at a higher temperature than the pure solvent. 3. Freezing Point Depression: Solutions freeze at a lower temperature than the pure solvent. 4. Osmotic Pressure: The pressure required to stop the flow of solvent across a semi-permeable membrane, which depends on the number of solute particles.
Classification of Solutions: Crystalloids vs. Colloids
Solutions are classified into crystalloidal and colloidal based on particle size.
Qualitative classification divides solutions into crystalloidal and colloidal. Previously, 2-500 nm was colloidal, <2 nm was solution, and >500 nm was suspension. Currently, crystalloids are defined as having particle sizes less than 1 nm, while colloids typically range from 1 to 100 nm.
Crystalloids have particles less than 1 nm and can pass through semi-permeable membranes.
Crystalloids are substances with particle sizes smaller than 1 nanometer. Due to their small size, they are able to readily pass through semi-permeable membranes. Examples include electrolytes, glucose, amino acids, fatty acids, urea, and uric acid.
Colloids have particle sizes between 1 nm and 100 nm and cannot pass through semi-permeable membranes.
Colloidal particles range in size from 1 nm to 100 nm. These particles are larger than crystalloids and are unable to pass through semi-permeable membranes (they are non-permeable). Colloids can be further classified into hydrophilic (solvent-loving) and hydrophobic (solvent-hating) types.
Hydrophilic colloids have an affinity for water, while hydrophobic colloids do not.
Hydrophilic colloids are solvent-loving and exhibit an attraction to water. Examples include proteins, polysaccharides, and bile salts. Hydrophobic colloids are solvent-hating and lack affinity for water.
Plasma colloids include proteins, lipids, antibodies, clotting factors, and various enzymes.
Key colloidal substances found in plasma, memorized by the acronym 'PLACES', are Plasma proteins, Lipids, Antibodies, Blood clotting factors, and Enzymes. Plasma proteins can be further remembered using 'GPF' (Globulins, Prothrombin, Fibrinogen) and lipids include various types of fats.
Common dietary colloids include starch, cellulose, glycogen, and proteins.
Dietary sources of colloids include common substances like starch, cellulose, glycogen, and various proteins consumed in food.
Differences Between Crystalloids and Colloids
Colloidal particles are larger than crystalloid particles and cannot pass semi-permeable membranes.
Colloids have larger solute particles compared to crystalloids. This size difference prevents colloidal particles from passing through semi-permeable membranes, whereas crystalloid particles can easily permeate them.
Crystalloids are crystalline and have definite shapes, while colloids are amorphous with no definite shape.
Crystalloid particles typically possess a crystalline structure and a defined shape. In contrast, colloidal particles are amorphous and lack a definite, fixed shape.
Colloids have lower osmotic pressure compared to crystalloids.
Colloidal solutions generally exhibit a lower osmotic pressure than crystalloidal solutions due to the larger size and potentially lower effective particle concentration compared to crystalloids at similar mass concentrations.
Colloids exhibit the Tyndall phenomenon and Brownian movement, which crystalloids do not.
The Tyndall phenomenon, where a beam of light passing through the solution becomes visible due to light scattering by particles, is characteristic of colloids. Brownian movement, a continuous, random motion of particles, is also observed in colloids. These phenomena are absent in true crystalloidal solutions.
Colloidal particles are generally not visible under a microscope and are non-digestible.
Most colloidal particles are too small to be seen with a standard light microscope and are considered non-digestible in biological contexts, unlike crystalloids.
Suspensions and Emulsions
Suspensions are mixtures where insoluble solid particles are dispersed in a liquid medium.
Suspensions consist of insoluble solid particles suspended in a liquid medium. These particles are larger than colloidal particles (typically >100 nm) and will eventually settle out if left undisturbed. Examples include some syrups and antibiotic suspensions that require shaking before use.
Emulsions are liquid-liquid colloidal systems, where one liquid is dispersed in another immiscible liquid.
Emulsions are a type of colloidal system involving two immiscible liquids, where small droplets of one liquid are dispersed within another. The particle size typically ranges from 100 nm to 1000 nm. Examples include milk of magnesia, curd, cod liver oil, and hair cream.
Emulsification is the process of converting large lipid droplets into smaller ones, often stabilized by an emulsifying agent.
Emulsification involves breaking down large lipid droplets into smaller ones to help them form a stable emulsion. An emulsifying agent facilitates this process and stabilizes the mixture, enabling fat particles to form an emulsion with water.
Properties of Colloids
Brownian movement is the continuous, random, zigzag motion of colloidal particles.
Brownian movement is characterized by the haphazard, continuous, and rapid motion of colloidal particles. This movement is caused by the incessant bombardment of the colloidal particles by the molecules of the dispersion medium (solvent).
The Tyndall phenomenon is the scattering of light by colloidal particles, making the light beam visible.
When a beam of light passes through a colloidal solution, the light rays become visible due to scattering by the colloidal particles. This effect, known as the Tyndall phenomenon, is not observed in true crystalloidal solutions where particles are too small to scatter light effectively.
Colloidal particles carry either a positive or negative charge, and have an isoelectric point (pI).
Colloidal particles possess an electrical charge, being either positively or negatively charged. At a specific pH value, known as the isoelectric point (pI), the net charge on the colloidal particle becomes zero. At this pH, the number of positive and negative charges is equal, forming a zwitterion. Colloids are least soluble and tend to precipitate out at their isoelectric point.
Electrophoresis is the movement of charged colloidal particles towards electrodes under an electric field.
Electrophoresis is a process where charged colloidal particles migrate towards an electrode with the opposite charge when an electric field is applied. Positively charged particles move towards the cathode (negative electrode), and negatively charged particles move towards the anode (positive electrode). This property allows for the separation of colloidal particles based on their charge.
Colloids have a larger surface area, facilitating greater adsorption.
Colloids exhibit a larger surface area relative to their volume compared to crystalloids. This increased surface area makes them highly effective for adsorption processes.
Sol-gel conversion is a physical property of some colloidal systems.
Some colloidal systems can undergo a reversible transformation between a liquid-like state (sol) and a semi-solid, gel-like state (gel). This sol-gel conversion is a characteristic physical property observed in certain colloids.
Fluid Balance and Osmotic Pressure
Colloidal Osmotic Pressure (COP) is vital for retaining fluid within blood vessels.
The COP, generated by colloidal particles like plasma proteins, creates an osmotic gradient that draws water into the blood vessels, counteracting hydrostatic pressure and helping maintain blood volume. A deficiency in COP can lead to fluid leakage into the interstitial space, causing edema.
Reduced COP can lead to edema and fluid accumulation in the interstitial space.
When COP decreases, the blood vessels lose their ability to retain sufficient water. This causes water to move from the plasma into the interstitial fluid, resulting in swelling, medically known as edema.
Increased COP can lead to more water being drawn into blood vessels.
An elevated COP pulls more water into the blood vessels from the surrounding tissues. This can increase blood volume and potentially cause blood vessels to expand, while cells may lose water and become dehydrated.
Dialysis
Dialysis separates colloids from crystalloids using a semi-permeable membrane and osmotic pressure.
Dialysis is a technique to separate colloidal substances from crystalloidal substances. It utilizes a semi-permeable membrane (like parchment or cellophane) through which crystalloids can diffuse due to osmotic pressure, while colloids are retained.
In renal failure, dialysis removes toxic crystalloids from the blood.
For patients with kidney failure, dialysis artificially performs the kidneys' function of filtering waste products. Toxic crystalloids, such as excess potassium ions or urea, are removed from the blood as they diffuse across the semi-permeable membrane into the dialysis fluid.
Blood cells and plasma proteins are retained during dialysis because they are colloids.
Blood cells (like red blood cells) and large molecules such as plasma proteins are colloids and are too large to pass through the pores of the dialysis membrane. Therefore, they remain in the blood during the dialysis process, ensuring they are not lost.
Quantitative Solution Classification and Osmolality
Solutions can be unsaturated, saturated, or supersaturated based on solute content.
Solutions are classified quantitatively as unsaturated (can dissolve more solute), saturated (cannot dissolve more solute at a given temperature), or supersaturated (contains more dissolved solute than normally possible).
Osmolality measures the total number of osmotically active particles in a solution.
Osmolality is a measure of the total concentration of osmotically active particles per kilogram of solvent (osmol/kg). It differs from molarity (mol/L) because it considers the number of particles after dissociation, not just the moles of the original substance. For example, 1 mole of NaCl dissociates into 2 particles, contributing 2 osmols, while 1 mole of glucose contributes 1 osmol.
Plasma osmolality is approximately 300 mOsm/L, with sodium being the major contributor.
The normal plasma osmolality is around 280-300 mOsm/L, averaging 300 mOsm/L. Sodium ions account for about 92% of this osmolality, making them the primary determinant of plasma osmolality. Other crystalloids contribute significantly, while colloidal substances contribute very little (approx. 1.5 mOsm/L).
Normal saline (0.9% NaCl) is isotonic to plasma.
Normal saline, a 0.9% solution of sodium chloride in water, has an osmolality of approximately 306 mOsm/L, which is very close to the plasma osmolality of 300 mOsm/L. This makes it an isotonic solution, meaning it has roughly the same osmotic concentration as blood plasma.
Isotonic solutions have the same concentration as plasma and do not cause significant water movement across cell membranes.
Isotonic solutions have an equal osmotic concentration to body fluids. When administered, they do not cause cells to swell or shrink because there is no net movement of water across the cell membrane due to osmosis.
Administration of Fluids and Tonicity Effects
Hypotonic fluid administration can cause water to move into cells, potentially leading to swelling or cerebral edema.
When hypotonic fluids are introduced into the body, they have a lower solute concentration than the intracellular fluid. This causes water to move from the extracellular space into the cells via osmosis, leading to cell swelling. If administered excessively, this can cause cerebral edema (swelling of the brain).
Isotonic fluid administration maintains cellular volume as there is no net water movement.
Administering isotonic fluids, like normal saline, results in no net movement of water between the extracellular and intracellular compartments. This is because the osmotic concentration of the fluid is similar to that of the body's cells, thus maintaining stable cell volume.
Hypertonic fluid administration causes water to move out of cells, leading to dehydration and cell shrinkage.
Hypertonic fluids have a higher solute concentration than the intracellular fluid. Consequently, water moves out of the cells into the extracellular fluid via osmosis, causing the cells to shrink and leading to dehydration. This can result in cerebral dehydration if the brain cells are affected.
Body Fluid Composition
A 70 kg person's body composition includes water, proteins, lipids, carbohydrates, and minerals.
The body composition for a 70 kg individual is detailed, showing the distribution of water (approx. 60% or 42 L), proteins (approx. 15% or 10.5 kg), lipids (approx. 15% or 10.5 kg), carbohydrates (approx. 1% or 0.7 kg), and minerals (approx. 4% or 2.8 kg).
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