PHSL 410B Lecture Notes - Lecture 10: Stage Name, Biomolecule, Thermodynamics
Chemistry 350 Final Exam Study Guide
What are the biochemical properties of water?
• Oxygen makes up 60-70% of cell mass
• Water makes up 60-90% of cell mass
• Covalent bonding: atoms are sharing electrons in outer shell to fill each atom’s outer shell
• Ionic bonding: transfer of electrons from one atom to the other atom—charged ions
• Covalent bond strength:
o Related to differences in atom electronegativities
o Distance of outer shell electrons from the nucleus
o The nuclear charge
• The differences in O and H electronegativities establishes a very strong covalent bond in water.
• But, great differences in atom electronegativities result in ionic bond formation (electrons transferred)
What is the structure and chemistry of water?
• Angle of H-O-H; bonds are 104.5, unequal charge or electron distribution (S+, S-) and H20 exhibits a dipole, bent,
tetrahedral.
net dipole
• If in H20 2e- are pointing up and 2e- are pointing down, the top has unbounded
e- pairs and bottom have shared e- pairs with one e- each from O and H.
What are the functional and structural features of the hydrogen bond?
• Hydrogen bond: weak intermolecular interaction that plays a role in the
structure and function of water and biological molecules.
o It is between a slightly positive hydrogen atom (covalently bonded to an
electronegative atom) and a slightly negative atom.
• The strength of a hydrogen bond (H---O; 20 KJ/mol) is weaker than a covalent
bond (H—O; 460 KJ/mol)
• Hydrogen bond is never made using a H covalently bonded to carbon
• Critical features of a hydrogen bond
o Defined length (2.8-3 A)
o Linear positioning (maintains H-bond strength)
• Liquid water can be formed with hydrogen bonds but these breaks easily (3.4 H-bonds on average)
• Solid water (i.e., ice) can also be formed (4 H-bonds on average)
Polar
• Water is very polar and created by the uneven
electron/charge distribution or its dipole
• Water dissolves in polar compounds which are usually
charged, can hydrogen bond and are hydrophilic.
• Polar compounds are also soluble in polar solvents.
• Hydration: water readily dissolves salts which stabilizes
cations/anions by weakening their electrostatic
interactions thus disrupting crystallization Na+ and Cl-
Nonpolar
• Non-charged, not electronegative and aliphatic carbon
chains/aromatic rings
• Hydrophobic, the tendency to coalesce or group together is referred to as the hydrophobic effect.
• The ordering of polar water molecules around non-polar molecules is minimized when multiple non-polar
molecules group together (i.e., when the molecules group together, disorder or entropy occurs)
o This is entropy driven.
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Document Summary
What are the biochemical properties of water: oxygen makes up 60-70% of cell mass, water makes up 60-90% of cell mass, covalent bonding: atoms are sharing electrons in outer shell to fill each atom"s outer shell. What is the structure and chemistry of water: angle of h-o-h; bonds are 104. 5, unequal charge or electron distribution (s+, s-) and h20 exhibits a dipole, bent, tetrahedral. net dipole. If in h20 2e- are pointing up and 2e- are pointing down, the top has unbounded e- pairs and bottom have shared e- pairs with one e- each from o and h. What are the functional and structural features of the hydrogen bond: hydrogen bond: weak intermolecular interaction that plays a role in the structure and function of water and biological molecules. What is the ionization of water: when h2o ionizes it can form h+ and oh-. The h+ can hydrate another molecule to form h3o+.
