BIOLOGICAL MOLECULES
THE BUILDING BLOCKS OF LIFE
MRS L. K. TEMBO
What are living
creatures made of?
Regents Biology
Elements of Life
• 96% of living
organisms are
made of:
carbon (C)
oxygen (O)
hydrogen (H)
nitrogen (N)
Why are we talking about
chemistry????
Well….., because everything you dofrom walking, to thinking, to digesting
your lunch- is a series of chemical
reactions! We have to understand
basic chemistry in order to understand
cell biology and genetics.
So, let the fun begin!!!!!
Levels of Biological Organization
 Everything is made of matter
 Matter is made of atoms
Hydrogen
1 proton
1 electron
Oxygen
8 protons
8 neutrons
8 electrons
Proton +
Neutron 0
Electron –
atom: smallest part/basic unit of matter
3 sub-atomic particles:
Proton (+), Neutron (0), Electron(-)
Element: a substance that cannot be
broken down into two or more different
substances.
*Over 100 known elements
*(about 26 elements compose all living
things - most abundant are: C, H, O, N)
atomic number : number of protons
atomic mass (mass number): The mass
of a single atom
It’s equal to protons + neutrons (ie..mass
of nucleus)
The World of Elements
Isotopes: elements with the same number of protons, but different
number of neutrons.
Radioactive Isotopes: have unstable nuclei – break down at a known rate,
give off radioactive particles (gamma rays, etc)
* Dangerous AND useful, too
* ex: fossil dating, bone scans, GI series, chemotherapy
Radioisotopes in Medicine
• Detect and treat cancer
• Kill bacteria that causes food to spoil
• “Tracers” to follow movement of substances within
an organism.
Ion : atoms that gain or lose electrons become
electrically charged
Compound: substance formed by 2 or
more elements in a fixed ratio
• physical and chemical properties of
compound are different
than atoms composing the compound
• Molecule: smallest unit of most
compounds consisting of 2 or more
atoms
Sodium
Chlorine
Sodium Chloride
Chemical Bonds
• Force that holds substances together
• Stability
• Forming and breaking bonds-provides
energy for growth, development,
adaptation, and reproduction
Types of bonds
• Covalent Bonds—formed by sharing of electron
pairs between atoms
– Two types of covalent bonds:
Non-polar Covalent: When covalently bonded atoms
share electrons equally
Ex: CO2
Polar Covalent: Electrons are shared unequally
between atoms, creating a polar molecule
Ex: H20
• Ionic Bonds—formed by transfer of electrons;
strong electrostatic force that binds positively and
negatively charged ions together
Molecules close together, slight attraction can form b/w oppositely
charged portion of nearby molecules- the intermolecular forces
--Helps form water droplets, geckos climb using structures on toes and
atoms on surface climbing.
VAN DER WAALS FORCES
-EX. HYDROGEN BONDS
• Hydrogen Bonds---much weaker than ionic or
covalent bonds results from unequal charge
distribution on molecules
• Ex: water to water (cohesion)
Mixtures: Solutions and Suspensions:
Mixture: composed of 2 or more elements or
compounds physically mixed, not chemically combined
(ex: salt and sugar together)
2 types of Mixtures:
a) Solution: where components are evenly distributed
(ex: salt water)
* water = solvent NaCl = solute
* polarity of water allows it to dissolve ionic
compounds and polar molecules (ex: salts, sugars,
minerals, gases, other solvents like alcohol)
b) Suspension: when materials don’t dissolve in water,
but break up into tiny pieces which do not settle out
(they are suspended by the moving water)
* ex: blood (water has dissolved compounds, blood
cells and other components (lipids) which remain
suspended in mixture)
The chemistry of life is sensitive to acidic and basic conditions
Acid: a compound that forms H+ ions in
solution
Base: a compound that produces OH(hydroxide) ions in solution
Acidity or Alkalinity (base) is measured on
the pH scale:
•
From 0 (most acidic) to 14 (most basic)
•
The pH of most cells is kept close to 7
(neutral) by buffers (substances that
resist pH change)
•
Each step on pH scale is a factor of 10.
(ex: pH 5 is 10x more acidic than?)
Buffer: weak acid or weak base which can
keep a pH stable
ex: Bicarbonate: most important
buffer in body- maintains homeostasis in
blood
When the number of H+ is equal to
the number of OH-  water
H+ + OH-  H20
Functional Groups
Functional groups
determine how a
molecule will
interact with other
molecules.
Why does sugar dissolve in water?
Important Functional groups in Biological
Molecules
 WATER
 Life’s chemistry is tied to water.
– All living organisms require water.
– The chemical reactions of your body occur
in cells consisting of 70–95% water.
Water
• A water molecule (H2O), is
made up of three atoms --one oxygen and two hydrogen.
H
H
O
Water is Polar
• In each water molecule, the oxygen
atom attracts more than its "fair
share" of electrons
• The oxygen end “acts” negative
• The hydrogen end “acts” positive
• Causes the water to be POLAR
• However, Water is neutral (equal
number of e- and p+) --- Zero Net
Charge
_
O
H
+
H
+
• Hydrogen bonds
form between
slightly positive
hydrogen atoms
and slightly
negative atoms.
Properties of Water
 Universal solvent
 Cohesion
 Adhesion
 Capillary Action
 High Specific Heat
 High Heat of Vaporization
 Less Dense as a Solid
UNIVERSAL SOLVENT
 Water is called the “universal solvent”
Definition:
• this means that water can dissolve more things than any
other substance.
Example:
• water can dissolve: soap, sugar, salt, toothpaste, baking
soda, etc.
• This allows for dissolving of materials in the cells/organism
• Allows for transportation of essential materials in the
cells/organisms
• “Like dissolves like.”
– Polar solvents dissolve polar solutes.
– Nonpolar solvents dissolve nonpolar solutes.
– Polar substances and nonpolar substances generally
remain separate.
Polar Ex: The
liquid part of your
blood, called
plasma, is about
95% water. The
solvent in plasma
is water and all
the dissolved
substances are
the solutes:
sugars and
proteins etc..
Nonpolar Ex:
Fats and oils
rarely dissolve in
water. Fats and
oils are nonpolar
so they do not
have charged
regions so they
are not attracted
to polar
molecules.
COHESION
Definition:
 the ability of water molecules to attract
towards each other.
– Because water molecules are polar (having one positive
end and one negative end), they attract each other.
Example:
 water “dome”
 rain drops
– This results in Surface Tension: the force that acts on
the particles at the surface of a material.
ADHESION
Definition:
 the ability of water molecules to attract to
other substances.
– Because water molecules are polar (having one positive end
and one negative end) they attract other substances.
Water will make hydrogen bonds with other
surfaces such as glass, soil, plant tissues, and
cotton.
 This allows for Capillary action -water molecules will “tow”
each other along when in a thin glass tube.
 Example: transpiration process which plants and trees
remove water from the soil, and paper towels soak up
water.
Example: Adhesion
helps plants transport
water from their roots
to their leaves
because water sticks
to the sides of cellular
structures in plants
called xylem.
Adhesion Causes Capillary
Action
Which gives water the
ability to “climb”
structures
High Heat of Vaporization
• Amount of energy to convert 1g or a substance
from a liquid to a gas
• In order for water to evaporate, hydrogen bonds
must be broken.
• As water evaporates, it removes a lot of heat
with it (cooling effect)
Water is Less Dense as a Solid
• Ice is less dense as a solid than as a
liquid (ice floats)
• Liquid water has hydrogen bonds that are
constantly being broken and reformed.
• Frozen water forms a crystal-like lattice
whereby molecules are set at fixed
distances.
More Properties…………..
• Refer to your text books for more properties of water and
their biological significance to living organisms.