WATER AND pH (Student notes).pdf

WATER AND pH CHEMICAL COMPOSITION OF LIVING MATTER WATER- 70-90%(free and bound water) SOLIDS- 10-30% INORGANIC SUBSTANCES- 1%(Na, K, Ca, Mg, NH4, Cl-, SO4, PO4, CO3 TRACES OF Fe, I2, Cu, Mn, Co, Zn are also present in combination with organic radicals Organic substances WATER -MAJOR component of t...

WATER AND pH CHEMICAL COMPOSITION OF LIVING MATTER WATER- 70-90%(free and bound water) SOLIDS- 10-30% INORGANIC SUBSTANCES- 1%(Na, K, Ca, Mg, NH4, Cl-, SO4, PO4, CO3 TRACES OF Fe, I2, Cu, Mn, Co, Zn are also present in combination with organic radicals Organic substances WATER -MAJOR component of the cell IMPORTANCE: Universal solvent An ideal biological agent or medium for the ionization of substances and therefore hastens chemical reactions Hydrogen bonding which enables water to dissolve many organic biomolecules that contain functional groups. It possesses a high latent heat of evaporation It has the capacity to conduct heat readily WATER AS A SOLVENT Water enables dissolved reactants to collide and form products. Water also dissolves waste products, which allows them to be flushed out of the body in the urine. Adhesion- water molecules stick to unlike surfaces such as glass or plastic due to H- bonds between water and other polar compounds. High Specific Heat- water can absorb or release large amounts of heat energy with little temp change. E.g. Water stabilizes temp. in cells and ecosystems. High Heat of Vaporization- many H-bonds must be broken before water can evaporate. Lower Density of Ice- water molecules in an ice crystal are further apart because of H- bonding. Water is Polar- a good solvent; surrounds ions and other polar molecules. E.g.Transport of nutrients in organisms- plasma, cytoplasm, and xylem. Medium for Chemical Reactions -hydration/dehydration reactions. Most biological activities occur in aqueous (water based)solutions. Water is able to dissolve small non polar covalent molecules, ionic compounds, and other polar covalent molecules Water soluble molecules are described as hydrophilic (water loving). Hydrophilic molecules dissolve in water. Those molecules that are not soluble in water are hydrophobic (water hating or fearing). Hydrophobic molecules – repel water.  Amphipathic molecules -have both hydrophilic and hydrophobic properties Water and hydrogen ions ACID, BASE, AND SALT Acids and Bases Weak Acids and Bases Equilibria Acid/conjugate base pairs Buffers Buffers Are a Combination of a Weak Acid and Base Buffers prevent pH shifts IONIZATION OF WATER Leads to the dissociation of molecules The reversible process results in the formation of H+ and OH- H2O