Biological Chemistry
• Life is made up of
matter
matter: occupies space
& has mass
Biological Chemistry
mass:
weight:
• Matter consists of chemical elements
Chemical Elements
• 92 naturally occurring
• 25 essential to life
Percentage (%) of body’s composition
THE TOP 10 ELEMENTS FOUND IN YOUR BODY
THE “BIG 4”
96% of your body
is composed of
these 4 elements:
Oxygen (65%)
Carbon (18.5%)
Hydrogen (9.5%)
Nitrogen (3%)
OTHER (4%)
Calcium
Sulfur
Phosphorus
Sodium
Potassium
Chlorine
• Trace amounts (less than
0.1%) of 15 other elements are
also found in the body
• Elements consist of atoms
atom: smallest unit of matter that still has
properties of an element
• Atoms are made of subatomic particles:
1) protons: positive charge
2) electrons: negative charge
3) neutrons: no charge (neutral)
THE ATOM: BASIC STRUCTURE
Nucleus
Hydrogen atom
1 Proton
0 Neutrons
1 Electron
Carbon atom
6 Protons
6 Neutrons
6 Electrons
Nucleus:
Proton Neutron Electron
Forces of attraction
between positive and
negative charges hold
the fast-moving
electrons (negative)
close to the nucleus
(positive).
Examples of Atoms
electron
proton
neutron
Hydrogen
1p+, 1e_
Helium
2p+, 2e_
• All atoms of a given element have same
number of protons = atomic number
Helium = 2 protons = atomic number =2
Carbon = 6 protons = atomic number = 6
• Same # protons & electrons, electrical
charge = 0, what is charge of He?
atomic mass: protons + neutrons
C = 6 protons + 6 neutrons = 12
isotope:
Importance of Electrons
• Determine how atoms interact
• Energy level differences, higher energy
farther from nucleus
electron shell: energy levels around nucleus
in which electrons are found
ELECTRON SHELLS AND ATOM STABILITY
ELECTRON SHELLS
Electrons move around the nucleus in designated areas
called electron shells. An atom can have as many as seven
electron shells in total.
First electron shell
(capacity: 2 electrons)
Second electron shell
(capacity: 8 electrons)
Vacancy
The chemical characteristics of an atom
depend upon the number of electrons in its
outermost shell.
Carbon
6p+, 6e_
Oxygen
8p+, 8e_
Sodium
11p+, 11e_
Chlorine
17p+, 17e_
How does a Reaction Occur?
• 2 atoms with incomplete e- shells,
give/take of e-, such that both atoms
gain full shells
Chemical bond: 2+ atoms attracted to one
another by a reaction
molecule: 2+ atoms held together by
chemical bond, e.g., water H2O
Types of Chemical Bonds
1) Ionic Bonds (e.g., NaCl = salt)
1 atom loses e- & 1 atom gains eResult = form ions or charged atoms
ionic bond: 2 ions with opposite charges
are attracted to each other
electron transfer
SODIUM
ATOM
11 p+
11 e-
SODIUM
ION
11 p+
10 e-
CHLORINE
ATOM
17 p+
17 e-
CHLORINE
ION
17 p+
18 e-
Types of Chemical Bonds
2) Covalent Bonds (e.g., H2O)
2 atoms share outer shell e- The number of single covalent bonds is
dependent on the # of e- needed to fill
the outer shell
COVALENT BONDS
OTHER EXAMPLES OF COVALENT BONDS
O2 molecule
Each oxygen atom
shares two electrons.
This is called a
double bond.
CH4
molecule
(methane)
There are several different ways of
representing molecular structure.
“Lewis”
model
“Ball-and-stick” “Space-filling”
model
model
Water: The Basis of All Life
polar covalent bonds: 2 atoms with very
different electronegativities (attraction
for shared e- in covalent bond) – results
in charged molecule (+ & - ends)
hydrogen bonds: H(+) attracted to O(-)\
WATER: HIGH SURFACE TENSION
Pressure applied to water surface
Hydrogen
bond
“V”-shaped water molecules are
held together by hydrogen bonds.
The bonds are just strong enough
to give water a surface tension
with net-like properties.
WATER: STRONG COHESIVENESS
300 ft.
6-ft.-tall
man
Water
molecule
released into
the
atmosphere
Water
molecules
pulled
upward
Water
molecule
pulled into
root system
Because of the cohesive
properties of water, trees
such as the giant sequoia
are able to transport water
molecules from the soil to
their leaves 300 ft. above.
As each water
molecule evaporates,
it pulls additional
water up through the
tree because of the
“sticky-ness” of the
hydrogen bonds that
link the water
molecules.
WATER: LOWER DENSITY WHEN FROZEN
FROZEN WATER
Hydrogen bonding arranges
water molecules into a
crystalline lattice, keeping
them slightly farther apart
and, therefore, less dense.
LIQUID WATER
Water molecules move
about freely, allowing them
to be closer to one another.
RELATIVE AREA
OCCUPIED BY THE
SAME NUMBER OF
H2O MOLECULES: Frozen water Liquid water
THE pH SCALE
H+ ion
ACIDS
1
2
Battery acid
3
4
5
6
Bases are fluids that have a greater proportion
of OH– ions to H+ ions.
• OH– ions bind with H+ ions, neutralizing
acids.
• Strong bases are caustic to your skin.
• Bases can be found in many household cleaners.
• Bases are generally bitter in taste and soapy.
7
8
Water
Beer
Soda
OH– ion
BASES
Acids are fluids that have a greater
proportion of H+ ions to OH– ions.
• H+ ions are very reactive.
• Strong acids are corrosive to metals.
• Acids break down food in your digestive
tract.
• Acids are generally sour in taste.
0
Water
9
10
Baking soda
Coffee
11
12
13
14
Bleach
Ammonia
Blood
 Soda, with a pH of about 3.0, is
10,000 times more acidic than a glass
of water, with a pH of 7.0!
SUMMARY: THREE TYPES OF BONDS
1 COVALENT BOND
A strong bond formed when atoms share
electrons in order to become more stable,
forming a molecule.
Strongest
Bond Strength
H2 molecule
2 IONIC BOND
An attraction between two oppositely
charged ions, forming a compound.
NaCl compound
3 HYDROGEN BOND
An attraction between the slightly
positively charged hydrogen atom of one
molecule and the slightly negatively
charged atom of another.
Weakest
H2O molecule H2O molecule
Four Macromolecules of Life
1) Carbohydrates (sugars = alcohol &
aldehyde or ketone)
2) Lipids (fats = alcohol & carboxylic acid)
3) Proteins (made of amino acids)
4) Nucleic Acids
How are Polymers Made?
Dehydration Synthesis
- “free” monomers have H & OH groups
- Add “free” monomers to polymer chain
= 1 H2O released
- Form new covalent bond between
monomers
* Make polymers (macromolecules) for
storage/transport, but cells must break
them down to monomers in order to use
them
Sucrose Formation
Glucose
(monosaccharide)
Fructose
(monosaccharide)
+ H2O
Sucrose (disaccharide)
How are Polymers Broken Down?
Hydrolysis (hydro = water; lysis = to break
- Reverse of dehydration synthesis
- Break covalent bond by adding water
- OH group to 1 monomer & H to
adjacent monomer
Major Polysaccharides
cellulose
glycogen
amylose (a starch)
COMPLEX CARBOHYDRATES
FORMATION
Bond(s) between
simple sugars formed
Glucose
DISACCHARIDES
Complex carbohydrates
formed by the union of
two simple sugars
Fructose
Sucrose
(table sugar)
Starch
(consists of hundreds
of glucose molecules)
DIGESTION
Bond(s) between
simple sugars broken
Sugars broken down further
ENERGY
Sugars broken down further
ENERGY
POLYSACCHARIDES
Complex carbohydrates
formed by the union of
many simple sugars
Fructose
Time
Blood sugar level
Depending on their structure, dietary
carbohydrates can lead to quick-but-brief or
slow-but-persistent increases in blood sugar.
Blood sugar level

Complex
carbohydrates
Time
DNA
• Double-stranded
• Sugar-phosphate
backbone
• Covalent bonds in
backbone
• H bonds between
bases