Chemistry of Life
Created by: J. Quigley
September 2013
Matter and Substances
• Every living and nonliving
thing is made up of matter.
• Matter is anything that has
a mass and takes up space
• To understand how living
things work and interact,
you must understand the
structure of matter
Atoms
• All matter is made of
atoms
• An atom is the smallest
unit of matter that
cannot be broken down
by physical means
• An atom has a positively
charged core
surrounded by a
negatively charged
region
Atomic Structure
• Atoms are made
of three types of
particles
– Protons: have a
positive charge
– Electrons: have a
negative charge
– Neutrons: Have
no charge
Elements
• An element is a substance made up of atoms that all
have the same number of protons…
– For example, each atom of carbon has 6 protons.
Chemical Bonds
• Valence electronselectrons in the
outermost level/shell of
the atom
• Chemical bonds form
between groups of atoms
because most atoms
become stable when they
have eight electrons in
the valence shell…
therefore they like to
give, take electrons or
share electrons
Compound
• A compound forms
• Sodium (Na) has an
when atoms of different
extra electron. Chlorine
elements bond, it is a
(Cl) is missing one
substance made of the
electron. When Sodium
bonded atoms of two or
gives its electron to
more different
Chlorine they become a
elements
compound and have a
chemical bond between
them…
Na + Cl = NaCl
Covalent Bonds
• A covalent bond is
when atoms SHARE
electrons
– Water is a covalent
bond.
– Remember atoms want 8
electrons in their outer
shell.
– Oxygen has 6, and each
hydrogen has 1.
– H2O has two hydrogen
and one oxygen
– 6+1+1 = 8 Electrons
• A molecule is a group of
atoms held together by
covalent bonds.
Ionic Bonds
• Atoms can also achieve
a stable valence level (8
electrons) by losing or
gaining electrons.
• When an atom loses an
electron it becomes
positively charged
• When an atom gains an
electron it becomes
negatively charged
• When an atom has
either a positive or
negative charge, it is
called an ION.
• The attractive force
between oppositely
charged ions is called an
IONIC BOND.
• The salt example is Ionic
Na+ + Cl- = NaCl
Polarity
• In some covalent bonds,
the shared electrons are
attracted more strongly
to one atom than
another. As a result, one
end, or pole, of the
molecule has a partial
negative charge while
the other end has a
partial positive charge
Polarity
• When a molecule, like
• When a molecule, like
water, has a partial
CH4, is totally balanced
negative and partial
and does NOT have any
positive side, it is said to
partial positive or
be POLAR
negative sides (oil,
grease, fat, wax)… it is
said to be NONPOLAR
Solubility
• Because of the charges involved, water can dissolve
POLAR molecules
• Nonpolar substances do NOT dissolve in water.
Hydrogen Bonds
• When bonded to
oxygen, nitrogen or
fluorine atoms, a
hydrogen atom has a
partial charge nearly as
great as a proton’s
charge. It attracts the
negative pole of other
nearby molecules
• This attraction is called
a hydrogen bond
• Hydrogen bonding plays
an important role in
many of the molecules
that make up living
things.
Water and Solutions
• A human can survive for a
few weeks without food,
but only a few days without
water. In fact, all of the
Earth depends on this
simple substance
• Most of the unique
properties of water result
because water molecules
form hydrogen bonds with
each other
Properties of water
• ICE FLOATS- when water freezes, hydrogen bonds lock
water molecules into crystal structure with empty
spaces. This makes frozen water less dense than liquid
water… allowing it to float
Properties of Water
• WATER ABSORBS AND
RETAINS HEAT: Hydrogen
bonds are constantly
forming and breaking
between water
molecules, because of
this, water can absorb a
large amount of heat
without changing
temperature… it is also
why water takes a
longtime to cool.
Properties of Water
• WATER MOLECULES STICK
TO EACH OTHER:
hydrogen bonds hold
water molecules together
much the same way hold
hands keeps a crown of
people together. This is
why small drops of water
make a ball.
• Cohesion- attraction of
particles of the same
substance. Water is
cohesive
Properties of Water
• WATER MOLECULES STICK
TO OTHER POLAR
SUBSTANCES: attraction
between particles of
different substances is
called adhesion.
• Adhesion is the attractive
force between two bodies
of different substances
that are in contact with
each other.
Solutions
• A solution is a mixture
in which two or more
substances are
uniformly dispersed
• Dissolving salt into
water creates the
solution: salt water
• Dissolved substances
can move more easily
within and between
cells
Acids and Bases
• Some water molecules break apart to form
ions.
• In pure water hydronium ions (H+) &
hydroxide ions (OH-) are present in equal
numbers
• In solution, some substances change the
balance of these ions.
ACIDS
• Acids: any compound
that increases the
number of hydronium
(H+) ions when
dissolved in water
– Lemons
– HCl (Hydrochloric acid)
– Vinegar
BASES
• Base: any compound that increases the number of
hydroxide (OH-) ions when dissolved in water
– Ammonia
– Antacid (tums)
– Hand soap
pH
• pH is a measure of how acidic or basic a solution is.
– The pH scale goes from 0 to 14.
• 0 is the most acidic possible
• 14 is the most basic possible
• 7 is neutral (neither acidic or basic)
Buffers
• The pH of the solutions in living things must
be stable. The pH of human blood is about
7.4. If the pH goes down to 7.0 or up to 7.8,
the person will die within minutes!
• A buffer is a substance that reacts to prevent
pH changes in solutions. It helps to maintain
the pH of a solution.
Carbon Compounds
• The parts of a cell are made up of large,
carbon based, complex molecules, often
called biomolecules.
– Lipids
– Proteins
– Carbohydrates
– Nucleic acids
Biomolecules
• A biomolecule is a large,
complex molecule built
from a few smaller,
simpler substances,
repeating units
arranged in an
extremely precise way.
• They are the molecules
of LIFE!
Carbohydrates
• A carbohydrate is a
biomolecule that
includes sugars,
starches and fiber
• It is made of carbon,
hydrogen and oxygen in
predictable rations
(CH2O)
• Sugars are the building
blocks of carbohydrates
Carbohydrates
• A single sugar molecule is
called a monosaccharide
– Glucose
• Two sugars can be linked
to make a disaccharide
– Sucrose and lactose
• Many sugars can be lined
to make polysacchrides
– Starch, cellulose and
glycogen
Carbohydrates
• They are a major source for quick energy
• Cellulose (a type of carbohydrate) is important
in providing structural support in shells and
cell walls
• The basic unit of a carbohydrate is a SUGAR!
Lipids
• Lipids are biomolecules that are made of fat
(waxes and steroids)
• The main function of lipids are to store energy,
control water movement and
insulation/protective coatings.
• Lipids also include steroid hormones, used in
signaling molecules.
Lipids
• Lipids consist of chains
of carbon atoms
bonded to each other
and hydrogen atoms,
they also have oxygen
• There are much fewer
oxygen atoms in lipids
than in carbohydrates
– Beef Fat (C57H110O6)
Lipids
• Lipids are insoluble (do not dissolve) in water
• They are made of a fatty acid and a glycerol
Proteins
• A protein is made of one or more chains of
amino acids that twist and fold into certain
shapes that determine what the proteins do.
• It is an important part of every single cell
• Proteins: provide structure and support,
enable movement, aid in communication and
help carry out chemical reactions
Proteins
• A protein molecule is
made of amino acids
• Every amino acid has an
amino group (NH2), a
carboxyl group (-COOH)
and a variable side group
(can be many different
things)
• The carboxyl group of an
amino acid can link with
the amino group of
another amino acid and
form a PEPTIDE BOND
Nucleic Acids
• All of your cells contain
nucleic acids
• Nucleic acid is a long
chain of nucleotide units
• A nucleotide is a molecule
made up of three parts:
– A Sugar
– A base
– Phosphate group
Nucleic Acid
• Nucleotides of
deoxyribonucleic acid, or DNA
contain the sugar deoxyribose
• Nucleotides of ribonucleic
acid or RNA, contain the
sugar ribose
Nucleic Acid
• DNA molecules act as “instructions” for the
processes of an organism’s life. These
instructions called the genetic code, depend
on the order of the bases in the nucleotides
that spiral around each other.
• Nucleic acids store and transmit hereditary
information
Nucleic Acid
• Some single nucleotides have important roles.
Cells need a steady supply of adenosine
triphosphate (ATP) to function.
• ATP is a nucleotide that has three phosphate
groups
• ATP releases energy when it breaks apart
Biological Reactions
• Living things carry out many chemical
reactions that help maintain a stable internal
environment. Many of these reactions require
large amounts of energy to get started. Many
of these reactions would not occur without
the help of enzymes
Enzymes
• An enzyme is a molecule that increases the
speed of a biochemical reaction
• Enzymes hold molecules close together and in
the correct orientation
• By assisting in necessary biochemical
reactions, enzymes help organism maintain
homeostasis, without enzymes, chemical
reactions would not occur quickly enough for
life to exist!
Enzymes
Metabolism
• Your cells get most of the energy needed for
metabolism from the food you eat. When food
is digested, it is broken down into small
molecules that enter the blood, which delivers
them to the cells.
• In the cells, chemical reactions release energy
by breaking down the food molecules so that
cells can use it