Why Study Chemistry in
Biology?
STARCH MOLECULE
GLUCOSE MOLECULES
You can prolong life by keeping bananas in cooler
temperatures.
I. Atoms
A. Definition: smallest part of matter: living and non-living
B. Composition
Subatomic
Particle
Charge
Mass
Location
Proton
+1
1
Nucleus
Neutron
0
1
Nucleus
Electron
-1
1/1840 the
mass of a
proton
Orbiting
nucleus
Bohr Atomic Model
Location of Electrons
outermost
electrons
participate in
BONDING
•Atoms Space
•Why if atoms have
so much space
can we be solid?
II. Elements
A. Definition: substance that cannot be broken
down into other substances
Mass Number
Atomic Mass
12.0107 amu
B. Biologically important
elements
i. Major: C H O N P S
Carbon
Hydrogen
Oxygen
Nitrogen
Phosphorus
Sulfur
ii. Minor:
Calcium
Potassium
Iodine
Chlorine
Magnesium
Radioactive Isotopes
Counting Atoms
C6H12O6
Element
subscript is the
NUMBER of
ATOMS
So in this molecule, there are 6 carbon atoms,
12 hydrogen, and 6 oxygen
III. Chemical Compounds
A. Compound definition:
a substance containing two or more
elements in a fixed ratio
– Ex: H2O, NaCl, CO2
B. Bonds:
i. Covalent Bonds:
• Electrons are shared to create a strong
bond
Cl2
ii. Ionic Bonds
• Transfer of electrons
between atoms to
create a bond
• Ion- an electrically
charged atom
• Gain electron; negative
charge
• Lose electron; positive
charge
LOSER
GAINER
JOKE- Don’t Have to write this.
• A NEUTRON walks into a diner and sits down to
order a meal.
• When the waitress brings the food over the
neutron says “Can you bring the check? I am in
a hurry!”
• The waitress replies, “Don’t worry
about it, there is NO CHARGE
for you.”
JOKE- Don’t have to write this.
• Two atoms walk down the street and collide.
• One atom says to the other, “Are you okay?”
• The second atom replies, “I think I lost an electron.”
• The first atom says, “Are you sure?”
• The second one says, “Yeah, I’m POSITIVE!”
iii. Extras
1. Molecule definition:
• Two or more atoms held
together by covalent bonds
• Can have different
properties when together
then when apart
LIFE DEPENDS ON THE UNIQUE
PROPERITIES OF WATER
Questions to think about
• Why do put salt on the roads?
• Why do we salt a pot of pasta water?
• At a higher altitude why must we
cook “boil” something longer?
Human Composition
• Cells are 70 to
95% water
Hydrogen Bond
• Weak attraction
between a slightly
positive and a
slightly negative
Plant Composition
• As much as 95%
plants can be made
of water
Formula and Bonds
Formula: H2O
Bonds: Covalentelectrons are
shared between
Oxygen and
Hydrogen
How do we get Hydrogen Bonds?
Because Oxygen has 8 Protons (+) it pulls the electrons more
(Electron HOG)
Oxygen acts Negative- Hydrogen acts Positive
O
H
H
Hydrogen Bonds
• Hydrogen Bondsweak bonds
slightly positive H
is attracted to the
slightly negative
O of another
water molecule
Polarity
• Polar molecule:
molecule in which
opposite ends have
opposite electric
charges
• Why? Water is a
polar molecule:
because Oxygen is
an electron HOG
The polar nature of water and the
effects of hydrogen bonding explain
most of water's unique properties.
•
•
•
•
•
Cohesion
Adhesion
Solubility
Temperature moderation
The lower density of ice
Cohesion
• Water “sticks” to each other
• Surface tension= when
cohesion pulls water
molecules at the surface
tightly together, forming a
film-like boundary
1-inch
papercli
p
over-filled water
3oz Dixie cup
Jesus Christ Lizard
Adhesion
• Water molecules
are also attracted
to certain other
molecules.
• Ex. In trees/plants
water goes against
gravity
Called capillary action
Water is the a Universal Solvent
Water is able to dissolve other Polar & ionic
compounds when mixed by causing the ions to
break away and surround them.
• Water dissolves Salt (Na+Cl-)
Temperature and Water
Boiling Point: 100 oC
• When you heat
molecules move faster
• When you cool
molecules move
slower
• Water takes more
energy to heat
because energy must
break hydrogen
bonds
212 oF
Does water boil faster if you add salt
to it?
• Yes or No- pollseverywhere
• Water Boils when it has enough energy for the
molecules to leave
Freezing Point
0 oC or 32 oF
• What would happen if
our oceans did not
have salt in them?
• Why do we put salt on
our roads?
• Why at effect does salt
have on FREEZING
POINT?
Homework Questions
1. Explain how the structure of water molecules results in
attractions among them. 2. Give an example of how
cohesion among water molecules is important to living
things. 4. Name three conditions on Earth that make the
planet suitable for life. 5. Explain one way in which water
can moderate temperature.
Why is this important for life?
Water Boiling Point
Ethanol Boiling Point
• Why are higher altitude must we cook “boil”
something longer?
•Why do we need salt
in our ice, when
making ice cream?
Watch Video
• http://www.youtube.com/watch?v=0eNSnj4Z
fZ8
• Review of Water Properties for Lab