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The Chemical Basis
of Life
All living things need water.
WHY?
• Universal solvent
• Dissolves necessary nutrients
• Used to produce enzymes and hormones
Necessary for life processes
• Can conduct electricity
Water is the universal solvent.
Remember polarity-uneven charge distribution
on a compound
electrons are shared on
different energy shells
electrons are shared unequally
(someone’s a bully)
Polarity is important to solubility-the ability
Of a solvent to dissolve a solute.
Ionic solutes: ionic solutes are made of ionscharged atoms—one negative, one positive
Water has a positive end and a negative end
which will exert attractive forces on the
solute
POLARITY
UNEVEN DISTRIBUTION OF CHARGES
Molecules tend to be asymmetric
__
+
On polar molecules, electrons are controlled by one
Of the atoms.
Polarity – the uneven distribution of charges on a molecule
uneven distribution is a result of:
a. Sharing of electrons between atoms with different energy
1. Asymmetric molecules are polar
This side or pole of the
Molecule has no
Electrons present.
The charge of the nucleus
Is felt making it feel
positive
Electrons are very
Present on this side
Of the molecule
That makes this side
Or pole of the
molecule
Feel negative
Hydrogen has one electron on the K shell
Fluorine has 9 electrons on the K and L shells. Fluorine is a larger atom with
More energy. F controls all of the electrons.
In the water molecule, hydrogen is a smaller atom with less energy
than oxygen.
When the electrons are share between these two atoms,
oxygen controls the electrons because it is an atom with more energy.
Because of this the molecule has two poles – one that feels positive
(hydrogen’s end) and the other that feels negative (oxygen’s end).
Well how does all this connect with solutions? The reason why solutes stay in solution
is because of polarity. Polar solutes dissolve most easily in polar solvents – water is polar
and so it can dissolve all polar molecules. Nonpolar solvents dissolve nonpolar solutes.
NaCl
Cl -
Na +
Cl -
Na +
Cl -
Cl Na +
Na + Cl - Na +
Cl - Na
Na + Cl Cl +
Na + Cl - Na +
Cl - Na +
Na
+
Na + Cl Cl Cl Na +
Cl Na +
Cl Na +
Cl -
Cl -
Na +
Cl Cl -
Cl Na +
NaCl is an ionic compound
that is made up of + Na
ions and - Cl ions.
NaCl
When an ionic compound
dissolves in water it is
called DISSOCIATION.
Molecules can also be nonpolar – an even distribution of charge on the molecule.
a. Sharing of electrons between atoms of equal energy
1. Diatoms
Here this diatom, electrons are on the same energy level. Electrons are on the same
energy shells and therefore are controlled equally by each atom. Electrons spin
equally around each nucleus.
If a non polar molecule is put into water, it will NOT dissolve because of the like
Charges that will meet in the water and the solute.
CH4 is a symmetric
molecule that is
non polar. It will not
dissolve in water
because it will be repelled
by the positive pole of
the water molecule.
Solutions are special kinds of mixtures
Let’s review!!
Element – pure substance
homogeneous throughout
only one kind of matter present
Compound – pure substance
homogenous throughout
made from 2 or more elements
chemical in nature
Mixture – can be homogeneous or heterogeneous
made from 2 or more elements, compounds, or both
physical in nature
Special solutions
Suspensions
• Made of solute/solvent
• Heterogeneous
• Solute is suspended in the solvent for
a period of time
• Solute will eventually settle out of
solution
• Oil and vinegar
• Chocolate milk
• Sand and water
• Blood
Colloids
• A special kind of suspension where
the solute is held in the solvent for
an extended time period.
• Homogeneous
• The use of an emulsifier is needed
to keep the solute in suspension.
• Mayonnaise
• Whipped cream
Acid base comparison
acid
base
• Any aqueous solution that
releases Hydrogen ions in
solution.
• Generally, any compound
that contains Hydrogen
• Will react with metals to
release Hydrogen gas.
• Has a pH between 1 and
6.9
• Tastes sour
• Turns blue litmus red
• Will react with a base to
produce a salt + water
• Any aqueous solution that
releases hydroxyl ions (OH)
in solution.
• Generally, any compound
that contains the OH ion.
• Has a pH between 7 and
14
• Tastes bitter
• Feels slippery
• Turns pink litmus blue.
• Will react with an acid to
product a salt + water.
Acid:
hydrochloric acid – HCl stomach acid
sulfuric acid
- H2SO4 car battery acid
nitric acid
HNO3 fertilizers
carbonic acid
H2CO3 acid found in sodas
Bases: sodium hydroxide – NaOH Drano
human blood
potassium hydroxide – KOH soaps
calcium hydroxide – Ca(OH)2 hair relaxer, remover,
Ca supplement in baby food.
Neutralization reaction:
Acid + base = salt + water
HCl + NaOH
pH 2
pH 14
NaCl
pH 7
+ HOH
pH 7
Compounds come in two types:
Inorganic-usually ionic
made of a metal and a nonmetal
soluble in water
high melting points
crystals and minerals
generally referred to as salts
Organic- always covalent
contain C, H, O H:O 1:2
many compounds that change shape
bonds are weaker than ionic but
are very stable.
Reactions that produce organic compounds:
1. polymerization production of large organic
compounds that are produced from
smaller compounds.
Monomer + monomer = polymer
Proteins and large carbohydrates are formed
through polymerization.
2. dehydration synthesis=when H and OH
Are removed from two compounds to form a
Larger molecule
glucose plus glucose = maltose + water
C6H12O6 + C6H12O6 = C12H22O11 + H2O
Dehydration means: to take water out
3. Hydrolysis reaction: a large molecule is
Broken down to form 2 or more smaller
molecules by adding water to the rxn.
Starch + water = smaller glucose molecules
All reactions require a specific amount of energy to produce
An activated complex=unstable atoms. The least amount of
Energy needed to produce this activated complex is the
Activation energy.
Exothermic vs endothermic
Catalysts work to supply more energy to a reaction thereby
Decreasing the amount of energy needed to produce an
Activated complex or specifically reducing the activation
Energy of the reaction. Catalyst make reaction proceed more
Quickly.
Enzymes are called biological catalysts and work the same
Way as chemical catalysts within living organisms.
Inhibitors work in the opposite way.
How enzymes work:
Terms to remember: active site, substrate, enzyme-substrate complex,
denaturation
4 necessary organic compounds for life
1. Carbohydrates: C.H.O
1. Monosaccharides - glucose
2. Disaccharides - sucrose
3. Polysaccharides – cellulose
Energy: immediate – simple
long term – starch
stored – as fat
Proteins:C, H, O, N, S
amino acids = monomers
enzymes
cell structure
peptide bonds
cellular repair, muscle formation, genes
Dehydration synthesis
Peptide bond-bond between carbon and nitrogen in a protein
Lipids:C, H, O
fats, oils and waxes – cholesterol
saturated and unsaturated
single bonds
double/triple bonds
energy: immediate and stored
Lipids are nonpolar covalent compounds = do not dissolve in water.
Important for the formation of membranes.
Will form liposomes-sphere that surrounds a small amount of aqueous
liquid. Sphere is formed from lipids.
Liposomes are important in the delivery of prescription medications,
cancer treatments, and nutrients.
Lipid sphere is made of a two sided molecule:
a head: hydrophilic
and a tail: hydrophobic
Nucleic acids: C, H, O, N
DNA, RNA
nucleotides: sugar (ribose), nitrogen base,
phosphate group (-PO4)
inheritance, cell function