The
Chemistry of Life
AP Biology
2007-2008
Why are we studying chemistry?
Chemistry is the foundation of Biology
AP Biology
What level of organization are
we now on?
atom
molecule
organ
tissue
Organ
system
AP Biology
compound
cell
organism
 Everything is made of matter
 Matter is made of atoms
Hydrogen
1 proton
1 electron
Oxygen
8 protons
8 neutrons
8 electrons
AP Biology
Proton
+
Neutron
0
Electron –
What are atoms made of?
 Each atom is made of protons, neutrons
and electrons
 Protons are positively charged particles
 Neutrons are neutral (they have no
charge)
 Electrons are negatively charged
particles
Draw the atom from
the board in your notebook
AP Biology
!
Why are electrons important?
 two atoms connect to each other
through the interaction of the electrons
–
–
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The World of Elements
H
C N O
Na Mg
P S
K Ca
Different kinds of atoms = elements
AP Biology
Life requires ~25 chemical elements
 About 25 elements are essential for life


AP Biology
Four elements make up 96% of living
matter:
• carbon (C)
• hydrogen (H)
• oxygen (O)
• nitrogen (N)
Four elements make up most of
remaining 4%:
• phosphorus (P)
• calcium (Ca)
• sulfur (S)
• potassium (K)
What is a compound?
 A compound is a substance made up of
atoms of two or more different elements.
This example is carbon dioxide
Draw the molecule
From the board
In your notebook!
Molecules are made of atoms. Compounds are
types of molecules!
AP Biology
Bonds in Biology
 Weak bonds

Hydrogen bond
H2O
hydrogen bonds
 attraction between + and –
 Strong bonds

H2O
covalent bonds
 two atoms share a pair or more of
electrons
 Both atoms are holding on
 Very stable and forms MOLECULES!
 More than one pair of elections =
double and triple bonds… VERY
STRONG!
 CARBON forms ORGANIC
MOLECULES
AP Biology
Covalent bond
–
–
H2 (hydrogen gas)
What is an example of Hydrogen
bonding in biology?
 A hydrogen bond is a
weak chemical bond.
* The strands of DNA are
bonded by hydrogen
bonds
AP Biology
Why do we need to know about
BONDS??
 Think back to levels of organization: when
we start with an atom and go to a
compound what is happening in between
the arrows?
 To go from an atom to an organism,
bonding must occur!
For example, BONDS form molecules from
atoms… like WATER!
Illustrate the bonds from
The board in your notebook!
AP Biology
WATER IS A MOLECULE!
All life occurs in water

AP Biology
inside & outside the cell
Water, water, water!
Water makes up the environment
AND a large part of the mass of most
organisms is water!
In human tissues, the percentage of water
ranges from 20% in bones to 85% in brain
cells!
 The water content is greatest in young
cells and decreases with age.
 About 70% of your total body weight is
water and about 95% of jellyfish and some
plants is water!

AP Biology
Chemistry of water
 H2O molecules form H-bonds
with each other (hydrogen)
+H attracted to –O
 creates a sticky molecule
 The charges cause water to ionize at times,
making H+ (acidic) and OH- (basic) which is
important in measuring pH of something.

AP Biology
What are organic molecules?
 All organic molecules contain carbon.
 Inorganic molecules do NOT contain
carbon (Ex: H2O)
 There are three main elements that are
present in all living things:



AP Biology
CARBON
OXYGEN
HYDROGEN
What are biomolecules?
 Large Organic molecules that exist in all
living things
 Also known as Macromolecules
(Macro=Large)
 They are life's building blocks
 All living things are formed from these
molecules
Draw the macromolecule
From the board
In your notebook!
AP Biology
Biomolecules are complex, but are
made up of simpler components
AP Biology
Biomolecules cont….
 Biomolecules start out small as
monomers and you add on to them to
build them up to become polymers
SMALL TO BIG
Mono= One
Poly= Many
AP Biology