General Biology
Chapter
p 2
Essential Chemistry for Biology
Why Learn Chemistry?
Its at the bottom of life’s hierarchy!
Matter: Elements and Compounds

Matter


Anything that occupies space and has mass
physical states






Solid
Liquid
Gas
92 Naturally occurring types of matter (elements)
Others have been man made!
Arranged by similarity in the periodic table

“Taxonomy for matter”
The Periodic Table… “modularity” of matter
“Elemental Differences”



What makes one element different from
another is the way its is “put together”
Atomic structural differences
differences..
Different structures = Different properties and
functions!


This concept is a re-occurring theme in biology!
Do you remember how atoms are put
together?
Atoms


Smallest unit of matter
Atomic structure made
f
from
subatomic
b
i particles
i l





Proton
Neutron
Electron
Where are they found in
the atom?
What properties do they
contribute
ib to the
h atom??
The Periodic Table
Figure 2.2
Drawing simple atomic structures…

Need to know the number of each subatomic
particle





Atomic number=number of protons(and electrons)
Mass number = number of protons + number of
neutrons.
How can you find
f
out the number off neutrons?
?
Place them in the appropriate location in the
atom
t
following
f ll i atomic
t i rules!
l !
Lets practice some.
The Periodic Table
Isotopes
D fi iti
Definition




Alternate mass forms
S
Same
number
b off electrons
l
and
d protons, b
but diff
different
number of neutrons
Stable isotopes aren
aren’tt a problem.
problem
Unstable isotopes = radioactivity (decay)

The nucleus ggivingg off particles
p
and energy.
gy (at
( a different
predictable rate)
Isotope Usefulness


Isotopes behave chemically
identical to nonradioactive
forms.
Biological
g
research


Tracers
Medicine

PET scans
Harmful Isotopes


Harm or mutate DNA
Where do they come from?


Nuclear accidents
Naturally occurring – radon
Matter: Elements and Compounds

Twenty-five elements are essential to life.

Four of these make up about 96% of the weight of the human body.


“Th Big
“The
Bi 4”
Trace elements occur in smaller amounts – but you still need them!
Matter: Elements and Compounds

Elements
 Cannot be broken down any further using chemical means
 Four main elements of life
 Oxygen
yg
 Carbon
 Hydrogen
 Nitrogen
Matter: Elements and Compounds

Trace elements are essential for life.

An iodine deficiency causes goiter.
Matter: Elements and Compounds

Compounds


Substances that contain 2 or more elements in a fixed
ratio
Atoms are held together by a force called the
chemical bond.

Examples of compounds


H2O
NaCl
Chemical Bonds

A chemical Bond

hydrogen
hydrogen
Oxygen
Definition
D
fi i i
 Union between the electron
structures of two or more
atoms; holds atoms together to
make molecules and compounds.
Types
 Covalent bonds
 Ionic bonds
 Hydrogen bonds
 Va
Van de
der Waals
Waa s force
o ce
Covalent Bonds



When two atoms share one or more electrons
Strongest type of chemical bond
Types of covalent bonds

Polar covalent

Unequal sharing


H,C to a N,O
N
Non-polar
l covalent
l t

Equal sharing


Identical atoms
C-H
Ionic Bonds



The attraction of
oppositely charged ions
from the stealing of
electrons by one of the
atoms.
Strongg when dry,
y weak
when wet!
Ion



Charged atom
“Cation” – positive charge
“Anion”
Anion – negative charge
Hydrogen Bonds




Stabilizing bonds
Found between hydrogen when its bonded to either
N or O, and another N or O somewhere else.
Very Transient, easily broken by HEAT.
Weak by itself, but strong when in numbers!
Van der Waals force
Natural attraction when atoms rub
together
 Sort of like “atomic
atomic friction”
friction
 Strength is usually weak unless there are
a lot
l off atoms “rubbing”
bb
together.
h



Based on surface area
Disappears completely when atoms are
separated
p
and not touchingg each other!
How do Geckos climb walls?
Chemical Reactions
Reactants


Breaking existing bonds and making new bonds!
Reactants


Products
Molecules used to make the product
Products

Resultant molecules formed from the reactants
Why is Water so Important?

Life on Earth began in water and
evolved there for 3 billion years.



Modern life still remains tied to
water.
Your cells are composed of 70%–
95% water.
The abundance of water is a major
j
reason Earth is habitable.
Water and Life

Structure of water



2 Hydrogen molecules
1 Oxygen
yg molecule
Bonds involved with making water

Polar covalent


Oxygen molecules pulls electrons stronger than hydrogen
molecules (intramolecular) within the water molecule!
Hydrogen bonds

Stabilize water molecules with each other (intermolecular)
between water
betwee
wate molecules!
o ecu es!
Water’s Life-Supporting Properties

The polarity of water molecules and the hydrogen
bonding that results explain most of water’s lifesupporting properties:




Water’s cohesive nature
Water’s abilityy to moderate temperature
p
Floating ice
Versatility of water as a solvent
Cohesiveness of Water

What is it?



Water is “sticky”
Due to hydrogen bonds
Why is it useful?


Water transport in trees
Creates surface tension (how
difficult it is to break the
surface)
Water and Temperature Moderation

Resists change
g in temperature
p






Heat energy is stored in the
hydrogen bonds between water
molecules ( g’zillions
g
of them))
Temperature increases when all
of the H-bonds have been
“affected”
Cooling: H- bonds release the
heat energy.
Importance?
Allows for global climates
Helps to regulate our body
temp (evaporative cooling)
temp.
Density Differences of Water Stages




Ice ((solid)) is less dense
than water (liquid)
Due to H – bonds
Ice floats on liquid water!
What if ice sank?
Ice
water
water vapor
Water’s Solvency

What is a Solution?


Solvent


Solvent + Solute
The dissolving agent
Solute

That which is dissolved
Consequences of Polarity

Water iss attracted
Wate
att acted to other
ot e polar
po a substances
s bsta ces



Example: sugar, salt
Hydrophilic: (“water loving”) substances that can
dissolve in water.
Water repels nonpolar substances


Example: oils
Hydrophobic: (“water dreading”) substances that cannot
dissolve in water
Osmosis – movement of water between
diff
different
water solutions
l i
through
h
h a membrane
b
Water always moves towards the solution with more solute!
We’ll see more of this phenomenon later!
Acids, Bases and pH

Acid

A compound that donates H+
(hydrogen ions) to a solution


Base

A compound that accepts a H+


More Hydrogen ions in solution
Less Hydrogen ions in solution
pH scale



Ranges from 0 – 14
Each pH unit is a ten fold change in
H+ concentration
pH 5 has 10 times the amount of
H+ ions as a solution of pH 6
Life exists in a narrow range of pH