Download chemistry - Old Saybrook Public Schools

CHEMISTRY
OF LIFE
Water
Carbohydrates
Lipids
Proteins
Nucleic Acids
DNA
Atomic Composition
No unique substances in
living things just different
amounts
“Same ingredients,
different recipes !”
Atoms
Basic unit of matter - matter is EVERYTHING
around us!! Some we see some we don’t.
Equal # of protons and electrons (subatomic
particles)
An element is made up of one type of atom
Living things are made up mostly of the
following elements; C, H, O, N, P, S
ATOMIC STRUCTURE
Nucleus
composed of
protons and
neutrons.
Electrons travel
in orbitals around
the nucleus.
Subatomic Particles
Subatomic
Particle
Proton
Neutron
Electron
Charge
Mass
+
1 amu =
1.6726x10-27 kg
0
1 amu =
1.6749x10-27 kg
_
0.000544amu =
9.11 x 10-31 kg
amu (atomic mass unit)
Mass of an electron
0.000000000000000000000000000000911 kg
Atoms are Neutral
Same number of protons and electrons
(#ELECTRONS = #PROTONS)
If the above is true then the charges are
balanced (# (+) charges = # (-) charges)
Does this look familiar?
Periodic
Table
Mendeleev
1869
Periodic Table
Families or Groups
Vertical columns -Example 1A; H, Li, Na, K, Rb, Cs
Similar electron configurations for this column (1A):
1 electron in the outer most electron shell
Similar chemical and physical properties
Electrons determine the chemical
properties of atoms
Arranged 1A - 8A
1A - 1 valence electron
8A - 8 valence electrons
Periodic Table
Periods or Rows
Not much in common except energies
of outermost electrons are similar
Atomic Mass
Total number of protons and neutrons in the
nucleus
Written as a superscript to the left of the
element’s symbol
Example:
12 C
Atomic Mass
(12.011)
Atomic Number
Number of protons found in the nucleus
Also equal to the number of electrons
# of protons = # of electrons (stable atom)
Written below the mass number
Atomic Number
12
6C
Atomic # < Mass #
Carbon
Nucleus
Mass Number = 12
p (6) + n (6) = 12
Atomic Number = 6
# p (6) = # e (6)
Electron
Orbitals
Electrons
Move in orbitals (levels or shells) that surround
the nucleus (electron cloud)
1st Level can hold 2 electrons
2nd Level can hold 8 electrons
3rd Level can hold 8 electrons
Valence electrons are the electrons in the
outer most orbital and are used to make
chemical bonds
Mass Number ?
Atomic Number?
Hydrogen
Nitrogen
Oxygen
Mass #
1
14
16
Atomic #
1
7
8
Electron #
1
7
8
Isotopes
Atoms of the same element but have a
different number of neutrons in the nucleus
Examples; 13C, 14C (Carbon 13 will have 6
protons and 7 neutrons)
Some are radioactive 13C is not but 14C is
Octet Rule
All elements gain or lose electrons so they
wind up with the same electron configuration
as the nearest noble gas ( He, Ne, Ar, Kr,Xe)
Noble gases are the stablest elements
Nonreactive
Example: O has 8 electrons (2 in 1st shell, 6 in
2nd shell) therefore it needs 2 electrons in its
2nd shell to be just like Neon
Ions
Atoms with extra electrons or missing
electrons
Atoms that are missing electrons are positively
(+) charged (more protons than electrons) also
known as cations
Atoms that have gained electrons are
negatively (-) charged (more electrons than
protons) also known as anions
Why are there charges on ions ?
Sodium (Na) has an atomic number of 11
and a mass number of 23
1st level = 2 electrons
11 electrons
2nd level = 8 electrons
p = 11
n = 12
3rd level = 1 electron
Na then has 1 electron floating in its outer orbital
making it easy for Na to lose that electron
When Na loses the electron it then has one more
proton than electrons giving it an overall +1 charge
Lets look at Oxygen (O)
Oxygen needs 2 electrons
to fill its outer orbital
When it takes on 2 more
electrons to fill that level it will
have 2 more electrons than
protons
Then it will have an overall charge of -2
Lewis Structures
A way of showing valence electrons
to better understand bonding
arrangements
Compound
Formed by the bonding of 2 or more elements
A chemical formula tells the composition of a
compound
Water (H2O) has 2 Hydrogen atoms and 1
oxygen atom
Atoms are held together by chemical bonds
Chemical Bonds
the 3 Tendencies
Tendency:
for electrons to occur in pairs
for atoms to balance positive and negative
charges
to fill outer shell with electrons
Covalent Bonds
Share Electrons
When atoms share 2
electrons it is a single bond
Sharing 4 electrons is a double
bond
Sharing 6 electrons is a
triple bond
CH4 Methane
Ionic Bonds
Transfer Electrons
NaCl - Salt
Chemical Bonds
Covalent bonds are the strongest type of
bond, forms molecules
Ionic bonds are attractions between oppositely
charged ions, not as strong as covalent bonds
Van der Waals Forces are intermolecular
forces between different molecules (an
example are hydrogen bonds between water
molecules)
Lets Practice !!
Water - elixir of life
Which living thing has the highest % of water?
97%
95%
Human 67% of body weight is water
Why do we need water?
Helps blood transport materials such as
oxygen and nutrients
Needed in catabolic reactions to digest food
and in anabolic reactions to build important
molecules such as muscle fibers
Regulates body temperature (Homeostasis)
Moistens tissues(eyes, nasal cavity, lungs, etc)
And the list goes on .........
Water Neutral Yet Polar
Neutral because
10 electrons balance
out the 10 protons
Polar because the electrons
want to be closer to the
oxygen with the 8 protons
Oxygen is more (-) charged with
the hydrogens more (+) charged
Dissociation of Water
1.67 x 1021
molecules in 1 drop
1 in 500 million dissociates
H2O --------> H+ + OHpH = 7 Neutral
Properties of Water
Polarity - uneven distribution of electrons,
electrons pulled towards the electronegative
oxygen atom
Adhesion - attraction between molecules of
different substances (why water travels up a
plant stem) (capillary action)
Cohesion - attraction between molecules of
the same substance (why water molecules
stick together)
Hydrogen Bonds (van der Waals)
Key to Life
Positive end of hydrogen
is attracted to the negative
end of another molecule,
such as oxygen
Weak forces but strong
when there are many.
This is why ice floats !
Ice less dense due to H bonds holding
oxygen and hydrogen apart
What would happen to life
on Earth if ice sank?
Mixture - different substances physically together but
aren’t combined chemically (bag of trail mix)
Solution - mixture where substances are evenly
distributed (Kool-Aid)
Solute - substance dissolved in a solution (Kool-Aid powder)
Solvent - substance that does the dissolving (Water)
Suspensions - mixture of water and non-dissolved
substances (Blood)
Acids
Examples HCl, Acetic acid, Uric acid, Citric acid
Acids form H+ ions in aqueous solutions, H+ is
highly reactive, wants an electron
pH scale measures the strength of acids and
bases
pH 1 - 6 is acidic
Bases
Examples NaOH, magnesium hydroxide,
bleach
Bases form OH- in aqueous solutions
pH 8 - 14
Buffers
Weak acids or bases that soak up
excess H+ or OH- in a solution,
they help to maintain homeostasis in a cell
Organic Chemistry
Chemistry of Carbon
Life is carbon based
20% of a living organism is carbon
Why Carbon?
It has 4 valence electrons
Has the ability to bond with 4 other elements
Can bond to other carbon atoms forming chains and
rings
Carbon does not ionize readily
Polymerization
Process by which small units (monomers) are added to
produce a macromolecule (polymer)
Monomer
Polymer
Macromolecules formed by
Dehydration Synthesis
+
OH
HO
O
H2O
Removal of water by enzymes to join molecules
Combines excess glucose (sugar) to make glycogen
(stored glucose) in muscles and liver
Hydrolysis
Process of using water to break down a
polymer
Occurs during digestion
Hydro - water
Lysis - to break
Macromolecules of Life
Carbohydrates
Proteins
Lipids
Nucleic acids
Carbohydrates
Plant based foods - sugars and
starches
Important as a short
term energy source
When bonds are broken during
digestion the energy is released
Carbs continued
Elements - C, H, O in a ratio of 1:2:1
Monomer - Monosaccharide such as Glucose
(C6H12O6) a primary energy source for our
cells or Fructose
Monosaccharide = 1 sugar
Dissacharide = 2 sugars
Polysaccharide = many sugars
Dissacharides
2 monosaccharides
Glucose + Fructose -----> Sucrose
Glucose + Galactose -----> Lactose
Famous Polysaccharides
Starch - plant storage form of glucose
(repeating units of glucose)
Glycogen -animal storage form of glucose
found in high concentrations
in the liver and your muscles
Cellulose - structural component of plants, found in
cell walls
Lipids Major Roles
Fats, oils and waxes
Used as a protective coating
Long-term high energy source
Component of biological membranes
Chemical messengers - steroids, hormones
made from cholesterol
Saturated / Unsaturated
Lipids
Elements - C, H, O
Monomers are glycerol and fatty acids
Unsaturated - at least 1 C-C double bond, liquid at
room temperature, plant and fish oils
Nucleic Acids
Store and transmit hereditary information
Elements - C, H, O, P, N
Monomers are nucleotides that are made up
of 3 parts (sugar, nitrogen base and phosphate)
DNA and RNA
Proteins
Needed for structure; hair, nails, bones
Messengers - receptors on cells
Immune system - antibodies
Catalyst - ENZYMES
Monomers are amino acids
Elements - C, H, O, N, S
Each cell has 100 - 1000 different proteins
Amino Acids - Monomers
of Proteins
20 found in nature, supplied by food
Connected by a peptide bond
All 20 can bond together to form many
combinations
All amino acids have a common structure
except have a different R group (side group)
Carboxyl Group
R Group
Amine Group
Dehydration Synthesis - chemical reaction that
removes water to create a polymer
Used to connect amino acids together to create a protein
Amino Acid #1
Amino Acid #2
Peptide Bond
Organization of Proteins
(Determines shape of the protein)
1st Sequence of amino acids
2nd Twists or folds in a chain
3rd chain folding back on itself
4th 2 or more chains aggregated together and
held by hydrogen bonds
Primary (1st) Level
The number and type of amino acid in the sequence
Secondary (2nd) Level
Beta pleated sheet
Fold in a chain
Alpha Helix
Twist in a chain
Tertiary (3rd) Level
Beta pleated
sheets
Alpha helices
One chain that folds in on itself
Quaternary (4th) Level
Hemoglobin (red blood cells) - 4 chains
Red are Heme molecules that capture
oxygen