Water and Electrolytes Lesson 2 PDF

WATER AND ELECTROLYTES Lesson 2 WATER AND ELECTROLYTES •Role of water in biological processes •Structure and properties of water •Compartments of body fluids and their constituents Role of water in biological processes • The most abundant substance in living systems  ≥70% of the weight • The...

WATER AND ELECTROLYTES Lesson 2 WATER AND ELECTROLYTES •Role of water in biological processes •Structure and properties of water •Compartments of body fluids and their constituents Role of water in biological processes • The most abundant substance in living systems  ≥70% of the weight • The course of evolution has been shaped by the properties of the aqueous medium in which life began WATER FUNCTIONS 1. Transports nutrients and oxygen into cells 2. Regulates body temperature 3. Universal dissolvent 4. Media where metabolic reactions take place 5. Structural component of macromolecules Structure of water • Geometry  Tetrahedron • Electric dipole • Oxygen nucleus attracts electrons more strongly than does the Hydrogen (a proton) • The oxygen atom carries a slightly negative charge and the hydrogen atoms carry a slightly positive charges. Electronegativity O >> H Structure of water-Hydrogen bonds • Electrostatic attraction between the oxygen atom of one water molecule and the hydrogen of another • Weak bonds • Short-lived groups • Hydrogen bonds are strongest when the bonded molecules are oriented to maximize electrostatic interaction  straight line Consequence Directional Bond Hydrogen bond: A weak electrostatic attraction between one electronegative atom (such as oxygen or nitrogen) and a hydrogen atom covalently linked to a second electronegative atom. Structure of water- Stages of water Tetrahedron  1 water molecule H-bonds 4 neighboring water molecules • Water vapor • Disordered • H-Bonds relaxed Solid phase Liquid phase Gaseous phase • “Flickering clusters” • Ice • Disorganized and in continuous motion • Regular crystal lattice structure • 4 H-bond • 3.4 H-bond Consequence ice is less dense than liquid water Properties of water 1. Water’s Polarity 2. High Heat Capacity 3. High Heat of Vaporization 4. High thermal conductivity 5. Highest density at 4ºC 6. Molecular movility  Osmotic effect 7. High Cohesive and Adhesive Properties  High surface tension 8. Universal solvent Functions of water 1. Structural component in macromolecules 2. Dissolves a variety of inorganic and organic molecules 3. Transports substances 4. Substrate or product in many enzymatic reactions 5. Thermal buffer Properties of water • Universal solvent Water is a polar solvent The ability to dissolve substances is determined by: 1. 2. 3. H-bond with polar groups in non-ionic molecules High dielectric constant  allow to dissolved ionic compounds Micelles formation when an amphipathic molecule is dissolved in aqueous solutions Hydrophilic: compounds that dissolve easily in water. Charged or polar compounds Hydrophobic: describes molecules or groups that are insoluble in water. Nonpolar molecules Amphipathic: molecules containing both polar and nonpolar domains. Properties of water • Universal solvent Hydrophilic molecules. Charged (ionic compounds) The negative ends of the water molecules attracts the cations (positively charged ions) from the ionic compound, and the positive ends attract the anions (negatively charged ions). Properties of water • Universal solvent Hydrophilic molecules. Polar molecules Polar substances, such as alcohols and sugars, also are soluble in water because of the hydrogen bonding. Properties of water • Universal solvent Amphipathic molecules Hydrophobic effect Hydrophobic: describes molecules or groups that are insoluble in water. Nonpolar molecules Hydrophobic effect: the aggregation of nonpolar molecules in aqueous solution, excluding water molecules Body water balance Body fluid homeostasis: Constant body water balance. The hormones aldosterone and antidiuretic hormone help to monitor blood volume through mechanisms regulating thirst and sodium and water balance. Body fluids compartements Intracellular fluid (ICF): fluid in the cytosol of cells Extracellular fluid (ECF): fluid exterior to cells; includes the interstitial fluid, blood plasma, and fluids found in other reservoirs in the body Interstitial fluid (IF): fluid in the small spaces between cells not contained within blood vessels Composition of body fluids Properties of water • Molecular mobility  Osmotic effect Osmosis: Bulk flow of water through a semipermeable membrane into another aqueous compartment containing solute at a higher concentration. Osmotic pressure: Pressure generated by the osmotic flow of water through a semipermeable membrane into an aqueous compartment containing solute at a higher concentration. Properties of water • Molecular mobility  Osmotic effect Important factor in the life of most cells Plasma membranes are more permeable to water than to most other small molecules, ions, and macromolecules Isotonic solutions: osmolarity equal to that of a cell’s cytosol Hypertonic solutions: higher osmolarity than that of the cytosol Hypotonic solutions: lower osmolarity than the cytosol Osmotic effect Osmotic effect Alterations in body fluid concentrations Dehydration Edema