Water and buffer Biology

Some substances are hydrophilic others are hydrophobic • – Hydrophilic - “water loving” (polar) • – Hydrophobic – “water fearing” (nonpolar) Ex: hydrocarbons ACID & BASE pH The Arrhenius Theory Svante Arrhenius defined acids as substances that dissociate in water to provide hydrogen ions and bases as substances that dissociate in water to provide hydroxide ions The Bronsted-Lowry (BL) Theory Johannes Bronsted and Thomas Lowry proposed a theory in which acids are defined as any hydrogen-containing substances capable of donating protons to other substances Bases are substances that accept and form covalent bonds with protons When a substance behaves as a Bronsted acid by donating a proton the substance becomes a conjugate base (1923) Acid is defined as any substance that can donate a hydrogen ion (proton) and a Bronsted-Lowry base is any substance that can accept a hydrogen ion (proton) Hydrogen bonding The Self-Ionization of Water Water, a hydrogencontaining material, is able to behave as both a Bronsted acid and a Bronsted base In pure water a small number of water molecules donate protons to other water molecules Water has a slight tendency to come apart and form H+ (hydrogen ion) and OH- (hydroxide ion), this is reversible • Ionization only occurs in out of every 500 million H2O molecules, however, it is biologically important ... Bronsted acid and a Bronsted base In pure water a small number of water molecules donate protons to other water molecules Water has a slight tendency to come apart and form H+ (hydrogen ion) and OH-... that dissociate in water to provide hydrogen ions and bases as substances that dissociate in water to provide hydroxide ions The Bronsted-Lowry (BL) Theory Johannes Bronsted and Thomas Lowry proposed... donate a hydrogen ion (proton) and a Bronsted-Lowry base is any substance that can accept a hydrogen ion (proton) Hydrogen bonding The Self-Ionization of Water Water, a hydrogencontaining material,