Supplemental Notes for Chapter 2

Basic Chemistry
Atomic number - number of protons
Atomic mass - number of protons and neutrons
- unit of atomic mass is daltons (d), 1d mass of H atom
- 1 gram atomic mass of any element = 6X1023 atoms
Molecular weight - weight expressed in atomic mass units or daltons (MW).
- weight of a mole of atoms or molecules. - 1 gram molecular mass = 1 mole 
= 6X1023 atoms
- glucose (C6H12O6) has a gram molecular weight of 180 daltons
Shells - energy levels that electrons occupy.
- divided into sublevels;- sublevels divided into orbitals; - orbitals 
hold a max of 2 electrons.
Radioisotopes - unstable isotopes (neutron # differs) that emit radiation
- Common isotopes used in biomedical research and clinical medicine;- 32P, 
35S, 3H, 125I.
- use of radioisotopes in medicine known as nuclear medicine.
Free radicals - atom containing a single electron in its outer orbital.
- React rapidly to fill unpaired orbital, thus exist for brief periods. 
- Common biological examples, superoxide anion O2-, hydroxyl OH, and 
nitric oxide NO.
Covalent bonds - stongest chemical bond between two atoms
- extremely important bond for producing protein structure, storing and 
liberating energy
- number of possible bonds for the four most abundant atoms in the body:  
Hydrogen - one, Oxygen - two, Nitrogen - three, Carbon - four
Body Composition : 99.3% H, O, N, C
0.7% essential minerals (Ca, P, K, S, Na, Cl, Mg)
0.01% Trace elements (Fe, I, Cu, Zn, Mn, Co, Cr, Se, Mo, F, Sn, Si, V)
Ionic bonds - formed when atoms gain or lose an electron to become - 
- cations (positive) or anions (negative) 
- ions in solution are called electrolytes
- bonds between opposite charges of a pair of ions are called ionic bonds.
- do not involve sharing an electron as in covalent bonds.
Hydrogen bonds: weak bonds between positive part of hydrogen and negative 
regions
of polar molecules (areas with high O or N density).
-While weak, these bonds are very important in determining molecular shape 
for most biological molecules.
Van der Waals forces - even weaker bonds than hydrogen bonds
- nonspecific attractions between the positive nucleus of any atom and the 
electrons of nearby atoms
- important in nonpolar regions
- important for intramolecular packing and thus supplement H bonds.
Polar Molecules - molecules with an uneven distribution of charge.
- some elements, particularly N and O, have a strong attraction for 
electrons 
- causes an uneven distribution of charge, with a positive end and a more 
negative end.
- can occur across a single bond, or across a very large molecule. 
- OTOH, non-polar molecules have a fairly even distribution of charge
Water : The chemistry of water is crucial to the functioning of living 
systems
- out of every 100 molecules in body, 99 are water.
-Water is a polar molecule.
-Water forms hydrogen bonds with itself (H to O), leads to surface tension
-Water molecules take part in many chemical reactions in living systems
Solutions: Solute = what dissolves, Solvent = liquid in which solute 
dissolves.
-In living systems, solvent is water - aqueous solution
-To dissolve, a substance must be electrically attracted to water.
-Polar molecules dissolve easily and are termed Hydrophilic
-Non-polar molecules do not dissolve easily, and are termed Hydrophobic
-Some large molecules are polar on one end, and non-polar on the other and 
are
termed Amphipathic. e.g. phospholipids
Acidity : Acidity refers to the concentration of free protons in solution
- too much H+ can interfere with hydrogen bonding, van der Walls
forces, and thus produce large changes in molecular interactions. 
- solutions are either acidic (high H+) or alkaline (low H+).
- molecules that release H+ (protons) are called acids
e.g. HCl = H+ + Cl- 
CO2 + H2O = H2CO3 = H+ + HCO3-
Carbonic acid bicarbonate
- buffer is any molecule that helps prevent large changes in H+
-Substances that accept a hydrogen ion are called a base
-Acids differ in their propensity to release protons.
Acidity is expressed with the pH scale where
pH = -log10 [H+]
- solution with [H+] = 10-7M has pH = 7
- lower pH is more acidic, higher pH is more basic