Unit I. Molecules & Cells
The Chemistry of Life
Water
A. Effects of Water’s Polarity:
Oxygen is more electronegative than
hydrogen. Electrons of the bonds spend more time closer to
the oxygen. This leads to a slight “-” Oxygen and a slight
“+” Hydrogen.
Since water is V shaped, w/ Oxygen at one
end and Hydrogen at the other, the opposite charges lead to
the molecule’s polarity.
1. Hydrogen Bonding – Occurs when the slight “+” of Hydrogen
of one of the molecules is attracted to the slight “-” of Oxygen
of the second molecule. Thus, holding the molecules together
1/20 the strength of covalent bond.
Lasts 1 trillionth of a second.
Each water molecule can form a total of 4 bonds w/ other
molecules.
2. Cohesion – Collective Hydrogen bonds which holds a
substance together.
3. Adhesion – Clinging of one substance to another.
4. Surface Tension – The measure of how difficult it is to stretch
or break the surface of a liquid.
5. Specific Heat – Amount of heat needed to change 1g. of a
substance by 1Co. Water’s relatively high specific heat enables
it to stabilize temperatures.
calorie – Amount of heat needed to change
1g. of water by 1Co.
Calorie – 1,000 cal or 1 kcal
6. Heat of Vaporization - a liquid absorbs a quantity of heat for
1g. of it to be converted from liquid to gas.
7. Evaporative Cooling - As a liquid evaporates, the surface of
that liquid cools. This results in temperature stability in
terrestrial organisms.
8. Ice Floats - Water, due to hydrogen bonding, is less dense as a
solid than as a liquid. Thus, ice floats. This prevents total
freezing of bodies of water.
9. Solvent of Life - (Not a universal solvent!)
Water dissolves ionic & polar molecules.
Ex. Blood, sap, sweat, urine
a. Hydrophilic - any substance w/an affinity for water.
b. Hydrophobic - any substance w/out an affinity for
water.
B. Effects of the dissociation of water molecules:
Simplified: H20 = H+ + OH1. Acid - Substance w/ increased H+ concentration.
2. Base - Substance w/ decreased H+ concentration.
3. Buffer - Substance that minimizes changes in H+
and OH- concentration.
Solute / Solvent Tonicity
Isotonic – Balanced concentrations
2 solutions w/same concentration. No movement of molecules.
Hypertonic – More concentrated solute.
Ex.
1.0M sucrose sol’n. is hypertonic to 0.2M sucrose sol’n
Hypotonic – Less concentrated solute.
Ex.
0.2M sucrose sol’n. is hypertonic to 1.0M sucrose sol’n
Hypertonic
Hypotonic
Isotonic
Water potential (likelihood of loosing water)
Water Potential =  
Solute Potential = s
Pressure potential = p
 = s + p
s = -iCRT

i = 1.0 constant
C = Concentration
R = 0.0831 constant
T = Temp oC + 273oK
Normally  = 0,  s = p
[ ] = 
Biochemistry
The study of the chemicals made and used by all living things.
Elements important to living things:
H, C, N, O, S, MG, P, Na, K, Ca, Mn, Fe, Zn
(In order of abundance w/in the universe)
Main chemicals made and used by all living things:
Carbohydrates (sugar)
Starch (Complex Carbohydrates, sugar)
Lipids (fat)
Proteins
Nucleic Acids (DNA, RNA)
Overview of each biochemical molecule
1. Carbohydrates (Sugar)
 Sufix “ose”
 Formula (CH2O)n
 Monosaccharides – simple sugars, one monomer
 Oligosaccharides – a few monosaccharides bound together
 Polysaccharides – Many monosaccharides bound together
a. Monosaccharide examples:
1. Glucose, C6H12O6
1. Ribose, C5H10O5
 Location of the H and OH are extremely important!
 Switching the location results in a different sugar being
formed.
Ex.
Glucose
Galactose
2. Starches – Polysaccharides, Complex Sugars
 Slightly more difficult to break down than simple sugars.
 Found in cellulose of plants, chitin of arthropods (algae
&fungi), Hyaluronic Acid, Heparin, and Chondriotin Sulfate.
 Dehydration synthesis forms bonds between monomers. H+
and OH- are removed from neighboring monomers and form
H2O and allow for the monomers to bond together.
c. Polysaccharide Examples:
1. Cellulose – -cellobiose repeating disaccharide
2. Chitin – N-acetylglucosamine repeating disaccharide
3. Lipids - (Fats , oils, waxes)
 Serve as protection, energy storage, & water proofing
 Comes in 4 main forms:
Triglycirides (fats & oils)
Waxes
Phospholipids
Steriods
a. Triglyceride – glycerol + 3 Fatty Acids
Glycerol
Fatty Acid
 Unsaturated fats have C-C double bonds
 Can be solid (animal fat) or liquid (veg. oil)
 C-H and C-C are higher energy bonds than C-O
 Energy release is more per unit than carbohydrates &
starch but slower.
b. Waxes: Soft but solid, ex. Cuticle, honeycombs
 Diff. structure than triglycerides
c. Phospholipids
 Has properties essential to the living cell
 Structure is like triglyceride but 1 fatty acid is replaced by
a phosphate.
 PO4 creates hydrophilic region
 Cell membranes are made of phospholipids bilayers
d. Steriods -
 Hydrophobic, dissolves in oils or lipid membranes
 Ex. Estrogen, testosterone, Vitamins A, D, & E,
cholesterol
(Not all cholesterol is bad, some is necessary w/in cell
membranes to allow passage of materials across the
membrane. Saturated fats build cholesterol. “LDL” is bad.
“HDL” is good.)
4. Protein
Amino Acid Monomers –
3 functional groups:
Amine (NH2),
Acid Carboxyl (COOH),
Rest Group (20 diff. variations)
Examples –
 Joined covalently through dehydration synthesis reactions to
form peptide bonds.
o Dipeptide – 2 bonded amino acids
o Polypeptide – Many bonded amino acids
 Chains of amino acids fold into 3D shapes to form proteins
 10 – 100 million different kinds of proteins
 Allow for different shapes and functions of living things
 Enzymes facilitate virtually all intracellular life processes