Chemistry of Life…and
some Biology
Fundamental Building Blocks
• Elements-can’t be
broken down by
chemical reaction
• Atoms-basic unit
of an element
• Atomic numberthe number of
protons in the
atom
Atoms
• Atoms are composed
of protons, neutrons,
electrons (e-)
• Electrons are located
in shells around the
nucleus.
• The electrons closest
to the nucleus are
held close, those
further away have
more energy and less
attraction to the
protons in the nucleus
Atoms and Their Energy
• As atoms get more
stable they have less
energy
• Atoms are more likely to
react with each other
when they have more
energy (i.e. less stable)
• An atom becomes stable
when its outermost
shell is filled or loses
enough electrons to lose
its outer shell
Which of the above are the most stable?
Atoms and Their Energy
• Lets look at sodium…
• Sodium (Na) has 11
protons (how can you
tell this?)
• In its free state it has 11
protons and 11 electrons
making it neutral.
• Due to lack of stability
the outer most electron
can be lost and Na can
have 11 neutrons and 10
electrons
• This is an ion, a charged
but stable atom
• In this case Na would
have a +1 charge
Bonding
• Atoms tend not to just
gain and lose electrons.
• For example for Na to
lose its outermost
electron it needs to be
around an atom that will
pick up, or gain, that
electron.
• Look at Chlorine (Cl) on
the chart. Can you see
why Na and Cl combine
to make NaCl?
• This is an example of an
ionic bond.
• There are 3 types of
bonds we will discuss:
• Ionic
• Covalent
• Hydrogen
Ionic Bonds
• Form between positive and negative ions
• One atom is losing an electron and another is gaining an
electron
• Strongest chemical bond
Covalent Bonds
• Sharing of electrons between atoms
• Less strong than ionic bonds
• Occurs when there are 2 or more reactive atoms that
both become stable by gaining electrons
• Rather than being selfish they share the electrons
Covalent Bonds
• There are many
important covalent
bonds in biology
• One of the most
common is the one
between Carbon (C)
and Hydrogen (H)
Covalent Bonds and Polarity
• Polarity occurs when there
is a slight difference of
charge across the molecule
• Polarity occurs when one
of the atoms has less of an
affinity for the electrons
than the other atom in the
bond
• Ex: in water oxygen (O) has
more affinity for the
electrons than the
hydrogen (H) does causing
a lightly more negative
area by the O and a slightly
more positive area by the
H.
Polarity and Hydrogen Bonds
• Due to this
polarity hydrogen
bonding can
occur. This is the
least strong of the
bonds we talk
about.
• These hydrogen
bonds give water
some of its
important
characteristics
Water
• Compounds will dissolve
in water if they:
• Are polar and will form
hydrogen bonds with the
water
• Are in an ionic bond
• These are hydrophilic
compounds
• Non-polar compounds
do not dissolve in water
and are considered
hydrophobic
• Water is the solvent in
this case and NaCl is the
solute
Table salt (NaCl) in Water (H2O)
pH Scale
• pH is referring
to the number
of H+ in a liquid
• In an acidic
solution there
are many H+
• In a basic
solution there
are many OHwhich grab up
the H+, thus
decreasing their
concentration
Concentration Gradient
• Difference in concentration of molecules in one
area compared to another
Diffusion
• Small substances
diffuse faster than
larger substances
• Heat increases
the rate of
diffusion
• The greater the
difference in
concentration of
two substances,
the greater the
rate of diffusion
Selective Permeability
• Selective about what
crosses based on:
• Size
• Electrical charge
• Other properties
Osmolarity
The Chemical Building Blocks of Life
• Four major classes of molecules are essential to life:
•
•
•
•
Carbohydrates*
Proteins*
Lipids
Nucleic acids
• Each of these molecules is made up of varying
combinations of carbon, hydrogen, oxygen, nitrogen,
phosphorus, and sulfur
*we will only talk about these today. We have talked about lipids, and
will talk about nucleic acids at a later date.
The Chemical Building Blocks of Life
• The vast array of biological
processes are dependent on a
carbon-carbon framework with
small amounts of other atoms
attached
• An organic molecule is one that
contains at least one carbonhydrogen bond
• Living cells contain many types
of organic molecules
The Chemical Building Blocks of Life
• Small organic molecules can bond to
other organic molecules to form
macromolecules
• Macromolecules are made up of
building blocks called polymers,
which contain small, repeating
organic molecules known as
monomers
• The properties of organic polymers
depend on the clusters of atoms
covalently bonded together, called
functional groups
Carbohydrates
• Sugars are a source of stored energy and are called
carbohydrates
• Sugars are found in almost every cell and is
involved in every chemical reaction that produces
energy in living organisms
Carbohydrates
• Glucose is a type of simple sugar called a
monosaccharide
• Table sugar is an example of a disaccharide, which is
formed when two monosaccharides, glucose and
fructose, are covalently bonded
• Polysaccharides are large polymers built by linking
many monosaccharides together
Carbohydrates
• Cellulose and starch are both found in plants and made
from glucose, but differ in the way the monosaccharides
are linked
• Glycogen is a highly branched polysaccharide that stores
energy in animal cells for rapid release when needed
Proteins
• Proteins are categorized by the function they
perform:
•
•
•
•
Storage
Structure
Transport
Catalysis
Proteins Are Built from Amino Acids
• All proteins are built from monomers called amino
acids
• There are 20 different amino acids that can be
arranged in a multitude of ways to construct the
variety of proteins needed for life
Proteins Are Built from Amino Acids
• Amino acids differ only
in the type of R group
that they include
• The R group gives each
protein its unique
properties and can vary
from having just one
atom to complex ring
structures
A Protein Must Be Correctly
Folded to Be Functional
• primary structure
• secondary structure
• tertiary structure
• quaternary structure
A Protein Must Be Correctly
Folded to Be Functional
• The sequence of amino acids in a polypeptide is
known as the primary structure
A Protein Must Be Correctly
Folded to Be Functional
• The secondary structure is created by the regional
folding of the polypeptide into three-dimensional
patterns
Is Secondary Structure that Important?
A Protein Must Be Correctly
Folded to Be Functional
• The tertiary structure is formed by the interactions
of distantly placed segments of the polypeptide
chain
A Protein Must Be Correctly
Folded to Be Functional
• Certain proteins have a
quaternary structure created
by the interaction of another
polypeptide chain
• Denaturation is the
destruction of a protein’s
three-dimensional shape,
resulting in a loss of protein
activity
• Extreme temperatures, pH,
and salt concentration can
cause denaturation of
proteins