Chemistry of Life
BIOCHEMISTRY

Biology = study of living things


WE ARE CHEMICAL MACHINES
Chemistry = study of MATTER
 what
it’s made up of
 how
it changes
 how
it combines
MATTER

Matter = anything that has mass &
takes up space
4
states = solid-liquid-gas-plasma
 Mass
= amount of matter in a substance
 Weight
= the force of gravity pulling on an
object’s mass
 Matter
is made up of ATOMS
ATOMS
 Atom
– smallest piece of stable matter
 Proton
= (+) Positive charge
 Neutron
= (0) Neutral
 Electron
= (-) Negative charge
In the nucleus
Orbits the
nucleus
ELEMENTS

Elements
 substance
made of only 1 kind of atom
 can’t
be broken down into simpler chemical
substances

EVERYTHING is made up of elements, even us!
The Elements

25 elements are essential to living
things.

96% of the mass of the human body
is made up of Carbon, Hydrogen,
Oxygen, and Nitrogen.

Trace elements like Na, K, P, S, and
Cl are present in living things in very
small quantities.
Think about it:

About 60% of the human body is made of water.
The chemical formula for water is H2O. That’s two
Hydrogen atoms for every Oxygen atom.

If this is true, how can it also be true that the mass
of the human body is 65% Oxygen and only 10%
Hydrogen?

Hint- what are some differences between an
atom of H and an atom of O ?
The Element Song
BONDING of ATOMS

Bonding = force that joins atoms together

An atom’s electrons will determine what
kind of bonds it will create

Atoms want a FULL outer energy level (shell)
 First
shell = 2
 Second
 Third

shell = 8
shell = 18
They will give, take, or share electrons in
order to fill their outer level
Types of Bonds…

Covalent bond = sharing electrons
 strong bonds, holds atoms together


Ex: O2 H2O
CO2
Ionic bond = electrons gains/lost
Not as strong, holds atoms together
 One atom becomes (+) and one becomes (-)
 Ex: NaCl CaCl2 K2O


Hydrogen bond
Weak, holds molecules together
 Forms between molecules with partial (+) and
(-) charges
 Water molecules form hydrogen bonds with
other water molecules

MOLECULES
 When
atoms bond together by
sharing electrons (COVALENT
BONDS), they form molecules
Chemical Reactions

Chemical reactions occur when
bonds are formed or broken, causing
substances to recombine into different
substances.

Chemical reactions occur in cells and
are all part of the organisms
metabolism

molecules that are important for life
are made and taken apart as part of
metabolism
Products and Reactants
2H2 + O2  2H2O
# of Reactants
=
# of Products