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Molecule of Life
Living organism are composed of matter
o Matter is anything that occupies space and has mass
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o Ancient Greek philosophers believed that existing materials on earth,
such as rock and soil, are composed of more than one materials, while
others such as a piece of iron, gold and silver, are made up of pure
substances
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o About 25 of these elements are essential to life
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SYMBOL

NAME

FUNCTIONS

Na

Sodium

Essential for nerve function

K

Potassium

Essential for nerve function

I

Iodine

Acts as a thermostat to regulate body
temperature

Md

Molybdenum

Needed by plants to incorporate nitrogen
into a biologically useful substance

Mg

Magnesium

Important component of bones, teeth, and
chlorophyll

Fe

Iron

Carrier of oxygen in the blood

o Other elements found in tiny amounts in living systems include iron,
molybdenum, selenium, vanadium, iodine, boron, chromium, fluorine,
silicon, chlorine, manganese, cobalt, copper, and zinc
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Their properties also differ, such as carbon
as black solid, sulfur as yellow solid, and helium as a colorless gas
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Bond
 A chemical bond is what holds atoms in a molecule together
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Three kinds of bonds are observed in
biological system
o Ionic bonds
 Ionic bonds are attractions between ions of opposite charges
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Ions are formed
because they are more stable when the outermost energy level is full
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o Covalent bond
 covalent bond is a chemical bond that involves the sharing of
electron pairs between atoms
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 Atoms bonded by sharing electrons
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o Hydrogen bond

 hydrogen bond (or H-bond) is a primarily electrostatic force of attraction
between a hydrogen (H) atom which is covalently bound to a more
electronegative
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o The different compounds found in living organisms can be grouped into
those containing carbon and those without
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o Organic compounds contain carbon
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WATER UNIQUE CHARACTERISTICS AND
FUNCTIONS OF WATER IN LIVING SYSTEMS
o Water is a universal solvent
 Water has the ability to dissolve many substances, including the
important molecules in biological system
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 An example, a salt is dissolved in water
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Water can dissolve the salt crystal
because its partially positively charge hydrogen is attached to the
salt’s positive sodium ion
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o Water molecules stick to each other and to surfaces
 Water molecules stick to one another through its hydrogen atoms in
a property called cohesion
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 It serves as a vehicle for the distribution of nutrients, gases, an other
substances of the body
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o Water has a high surface tension
 Due to its hydrogen bonding, water molecules strongly attract each
other, particularly on the surface of water than the air above
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This is a cooling
mechanism when you sweat
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o Water has high heat of fusion
 large amount of heat must be removed from liquid water to turn it
into solid state or ice cause of this property, organisms are protected
from freezing at low temperatures
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 Water has a dynamic structure wherein its molecules in liquid state
are there to move about
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o Water is a lubricant
 Water prevents friction in joints during movement, in the heart during
contraction and in the intestines during digestion
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Other Inorganic Compounds
o Some covalent bonds of compounds break spontaneously into ions when
dissolved in water
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This produces a positively charged (H) particle called
Hydrogen ion, and a negatively charged (OH) particle called Hydroxide
ion
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o Biologists measure hydrogen ion concentration on a pH potential of
hydrogen ions) scale, which ranges from 1-14 and describes the acidity of
a substance
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Acids have
sour taste and they turn litmus paper to red
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o Lungs allow accumulation of carbon dioxide in the blood when you the
hold your breath, forming carbonic acid
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o Bases have a bitter taste and are slippery
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o Common bases include sodium hydroxide in soap, ammonium hydroxide
in ammonia, and magnesium hydroxide in laxatives
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The pancreas produces
sodium bicarbonate and releases it into the small intestine to neutralize the
acidity in the food that come from the stomach
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o The concentration of hydrogen ions is important to living systems because
chemical reactions in the body driving life processes, such as food
digestion, depends on specific concentrations of these ions
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It is formed
when a base and an acid reacts together

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