Weakest of all bonds water solvency o the ability to

weakest of all bonds
Water
 solvency
o the ability to dissolve other chemicals
o Water is the Universal Solvent
 Hydrophilic – substances that dissolve in water
 molecules must be polarized or charged
 Hydrophobic - substances that do not dissolve in water
 molecules are non-polar or neutral (fat)
 Virtually all metabolic reactions depend on the solvency of water
 Water as a solvent
 polar water molecules overpower the ionic bond in Na+ Cl-
o forming hydration spheres around each ion
 note the orientation of the molecules
 cohesion
o tendency of like molecules to cling to each other
o water is very cohesive due to its hydrogen bonds

o surface film on surface of water is due to molecules being held together by a
force called surface tension
 adhesion
o tendency of one substance to cling to another
 chemical reactivity
o is the ability to participate in chemical reactions
 water ionizes into H
+
and OH
-
 water ionizes other chemicals (acids and salts)
 water involved in hydrolysis and dehydration synthesis reactions
 thermal stability
o Water helps stabilize the internal temperature of the body
 has high heat capacity – the amount of heat required to raise the
temperature of 1 g of a substance by 1 degree C.
 calorie (cal) – the amount of heat that raises the temperature of 1 g of
water 1 degree C.
 hydrogen bonds inhibit temperature increases by inhibiting
molecular motion
 water absorbs heat without changing temperature very much
 effective coolant
 1 ml of perspiration removes 500 calories
Acids, Bases, and pH
 An acid is proton donor (releases H + ions in water)
 A base is proton acceptor (accepts H + ions)
o releases OH- ions in water
 pH
o a pH of 7.0 is neutral pH (H + = OH-)
o a pH of less than 7 is acidic solution (H
+
> OH-)
o a pH of greater than 7 is basic solution (OH- > H
+
)
o measurement of molarity of H + [H+] on a logarithmic scale
 pH scale invented by Soren Sorensen in 1909 to measure acidity of beer
 pH = -log [H
+
]
o a change of one number on the pH scale represents a 10 fold change in H +
concentration
 a solution with pH of 4.0 is 10 times as acidic as one with pH of 5.0
 a solution with pH of 3.0 is 100 times as acidic as one with pH of 5.0
o Our body uses buffers to resist changes in pH
 slight pH disturbances can disrupt physiological functions
Metabolism
 All the chemical reactions of the body
 Catabolism
o energy releasing ( exergonic ) decomposition reactions
 breaks covalent bonds
 produces smaller molecules

 releases useful energy
 Anabolism
o energy storing/building (endergonic) synthesis reactions
 requires energy input
 production of larger molecules
 driven by energy that catabolism releases
 Catabolism and Anabolism are inseparably linked
Organic Chemistry
 Study of compounds containing carbon
 4 categories of carbon compounds:
o carbohydrates
o lipids
o proteins
o nucleotides and nucleic acids
Organic Molecules and Carbon
 4 valence electrons
o