Download Atom - Phoenix Union High School District

THE CHEMISTRY OF LIFE
Review/Background
Information
Important Words
Elements – pure substances that
cannot be broken down any
further.
Atom – the smallest unit of an
element.
Important Words
Molecule – a substance made up
of more than one atom.
Compound – a substance made
up of two or more different
Important Words
Ion – an atom that has a different
number or electrons (and thus
has a charge).
Isotope – an atom that has a
different number of neutrons.
Important Words
Covalent Bond – a molecule
where atoms share electrons.
Ionic Bond – a compound where
atoms transfer electrons.
The Atom
“Parts” of the atom
Neutron (0 charge)
Proton (+ charge)
Electron (- charge)
The basic structure of an atom
The Nucleus
 Central core
 Consists of protons
and neutrons
 Contains most of the
mass of the atom
The Protons
 Positively charged
 IN the nucleus
 Weigh 1 dalton
The Neutrons
 Are neutral (no charge)
 In the nucleus
 Weigh 1 dalton
The Electrons




Negatively charged
Weigh 1/2000 dalton (super tiny!)
little or no mass
Travel at very high speeds at various
distances (energy levels) from the nucleus
Atomic Number - the # of protons
Atomic Mass – the # of protons +
Neutrons
Energy Levels
 Atoms have energy levels
 The 1st level holds 2 electrons
 The next 6 levels hold 8 electrons
(octet rule)
There are more than 100 elements
(92 naturally occurring)
The Periodic Table
Common Elements in Biology
 Calcium
 Carbon
 Chlorine
 Copper
 Fluorine
 Hydrogen
 Iodine
 Iron
 Magnesium
Ca
C
Cl
Cu
F
H
I
Fe
Mg
 Phosphorus
 Nitrogen
 Oxygen
 Potassium
 Silicon
 Sodium
 Sulfur
 Tin
 Zinc
P
N
O
K
Si
Na
S
Sn
Zn
The most frequently occurring
elements in living things are:
Oxygen (65%)
Carbon (19%)
hydrogen (10%)
Nitrogen (3%)
Other important elements
Sulfur
Calcium
Phosphorous
Iron
sodium
Sulfur
Can be found in some amino acids.
Phosphorous
A component of ATP
Forms DNA
Calcium
Cell structure in prokaryotes and plants
Necessary for healthy bones
Involved in the transmission of nerve
messages
Iron
Helps form chlorophyll in plants
Makes up hemoglobin (helps oxygen
transport in red blood cells)
Sodium
Can help in photosynthesis
Helps transport glucose across the
membrane
Water
Water is Important to Life!
Water covers ¾ of the Earth.
It is the most abundant
compound in living things.
It is essential to life!
What makes water special?
Water is POLAR – the oxygen atom
attracts more of the electrons than the
hydrogen atoms do.
POLARITY
The structure of the water molecule
Covalent bond
The nucleus of oxygen is larger and has a
greater charge (+8) than the hydrogen
nucleus (+1).
The electrons that are shared are found
“closer” to the oxygen nucleus.
This creates a polar molecule – the
oxygen side is lightly negative and the
hydrogen side is slightly positive.
This polarity results in hydrogen bonds
Weak bond between the H of one
molecule and the C of another molecule.
Hydrogen bonds
Because of the bonds, water has some
unique properties!
Water “mini-lab”
Properties of Water
1. Cohesive properties
2. Thermal properties
3. Solvent properties
Cohesive properties
Cohesion - Water molecules
Sticking together
Cohesive properties
The way plants transport water through
their tissues is called transpiration and
depends on the cohesive nature of water.
Thermal properties
Water has a high
specific heat capacity
(the amount of heat
required to change a
substance’s
temperature).
Thermal properties
A body of water is thermostable.
Water maintains its temperature relatively
well and has less variation in temperature
than air and land.
Thermal properties
Water acts as a coolant.
It absorbs heat before it evaporates and in
doing so reduces body temperature.
Heat from chemical reactions can be
removed, to protect enzymes.
Blood can carry heat to cold parts of the
body.
Solvent properties
Because water is
polar, it is strongly
attracted to ions.
This has the effect of
isolating one ion from
another (which is
commonly known as
solubility).
Dissolving Salt
Water is the solvent of blood, tissue fluid
and cytoplasm.
It allows the transport of soluble minerals,
carbohydrates, amino acids, etc. that
organisms need to survive.
Other unique things about water
Water expands as it freezes
(ice floats)
The universal solvent (lots of things
can dissolve in it)
Adhesive
Part of biogeochemical cycles
Essential to life