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Module A Unit 2
Chemical Basis for Life
The Chemistry of Life
- Elements and Atoms
Subatomic Abbr.
Particle
proton
p+
Charge Mass
positive 1amu
neutron
n0
neutral
electron
e-
negative 0amu
1amu
Ions:
Atom with too few
electrons, positive
charge cation, or too
many electrons,
negative charge, anion
- Elements and Atoms
Why unstable?
Outer orbital, valence electrons,
are not full
- Atoms, Bonding, and the Periodic Table
What is C’s atomic number?
How many electrons are needed in the outer orbital to be
stable? 8
- Ionic Bonds
- Covalent Bonds
- Covalent Bonds
- Covalent Bond Types
- Covalent Bonds and Polarity
Why are the electrons pulled?
The larger nucleus of oxygen pulls
hydrogens’ electrons toward it.
Properties of Water due to its
polarity
Cohesion
Adhesion
Nearly Universal Solvent
Why do oil and water not mix?
High Specific Heat (thermal capacity)
NaCl = ?
Na+ + Cl-
Disassociation/Dissolving =
Ion formation
The picture shows a droplet of water
hanging on the tip of a leaf. How do
the physical properties of water
result in the image shown?
Cohesion: water forms a droplet
Adhesion: water “sticks” to the leaf
Van der Walls Forces: force of
attraction due to charge
Example: DNA double helix
Hydrogen Bond Interactions
Solid (frozen) water
Increase Volume, Decrease Density
Liquid water solution
Why is it important solid water floats in biology?
Ice insulates liquid water below allowing for life to occur.
When lettuce is frozen and then thawed, it’s texture changes. Using the image
above, why does freezing cause this change?
Central vacuole bursts when frozen, causing the leaf cells when thawed to
lose turgor pressure and become limp.
- Acids and Bases in Solution
pH: inverse log scale of hydrogen ion
concentration.
1 change in unit on a pH scale is a ten fold change
in H+ so 5 to 6 is a decrease 10X in H+ , 5 to 7 a
100X in H+
Affects enzyme activity and therefore cellular
chemical reactions
Neutralization Reaction
NaOH solution =
Litmus paper
HCl(sol) + NaOH(sol) 
HCl solution =
- Properties of Carbon
Organic Molecules:
always have ___C___ and ___H___
always form ___covalent______ bonds
- Carbon Compounds – Bond types
- Life With Carbon Monomers
- Life With Carbon
Hydrolysis (digestion) vs. Dehydration synthesis
Polymer  monomers
Monomers to Polymer
Polymers: long chain compound made of
repeating units
Monomers: subunits of a polymer
Autotrophs
Only organisms
that have the
ability to make
their own monomers
vs.
Heterotrophs
Get polymers to
digest monomers
either directly or
indirectly from
autotrophs,
“eaters”
- Life With Carbon
Uses:
Cell and organelle membranes
Energy storage as fats in animals
Waxes and oils in plants and
animals
- Life With Carbon
Hydrophilic – water loving head end
Hydrophilic – water hating end
What are the uses of fats in a single cell compared to a whale?
single cell – energy storage
whale, blubber for warmth
- Life With Carbon
Characteristics:
Why do insects and plants have waxy coatings?
Is wax a saturated or unsaturated fat?
Characteristics:
Lipids as Chemical Messengers = Hormones
- Life With Carbon
Example of a carbohydrate
Uses: starch plant energy storage and cellulose plant cell walls
glycogen – animal energy storage, mostly in liver and muscles
MONOSoluble
Glucose
Primary energy source in cells
Fructose
Fruit sugar
Galactose Component of lactose
Sucrose
DISoluble
Common table sugar; transported in the
phloem of green plants
(glucose + fructose)
Saccharides
Maltose
Least common natural disaccharide, but an
important polysaccharide intermediate
(glucose + glucose)
Lactose
Milk sugar
(glucose +galactose)
Glycogen Animal energy store in the liver
POLYStarch
Insoluble: giant
glucose polymers
Plant energy store; mostly contained in
granules in chloroplasts
Cellulose Main component of plant cell walls
- Life With Carbon
- Life With Carbon
Use: Codes for
amino acid
sequence for protein
synthesis
DNA: Double helix
nucleotide base pairing:
Adenine - Thymine
Cytosine – Guanine
Hydrogen bonding holds the two
complimentary strands together
RNA: Adenine - Uracil
Cytosine – Guanine
Types: mRNA carries genetic
code into cytoplasm
tRNA carries amino
acids to mRNA for protein
synthesis
- Life With Carbon
G – Guanine
C – Cytosine
T- Thymine
A - Adenine
Base Pairing – Van der Walls Forces
- Life With Carbon
Gene – group of codons instructing the formation of a functional protein
- Life With Carbon
Peptide Bonds
C-N
Holds amino acids
together to form
proteins. Ribosomes
use energy as ATP
- Life With Carbon
mRNA code after DNA to mRNA transcription
3 bases of mRNA codes for 1 specific amino acid
- Life With Carbon
Amino Acids (AA’s)
Known: over 60
In Cells: around 20 in living things,
another reason for the idea of
evolution
common descent - all life is
descended from one prokaryotic cell
Formed in the Golgi
Due to polar and
non-polar amino
acids
- Life With Carbon
Uses:
Cell structure :
Transport proteins
Glycoproteins for cell
recognition
Adhesive proteins to hold
cells together in
multicellular organisms
Enzymes for chemical
reactions – affected by
temperature, pH and
pressure
Shape Dictates Function!!!!!!
Activation Energy: energy required
to start a chemical reaction. It is
lowered by the enzyme allowing the
reaction to occur or speed it up
Reactants: left side of a chemical
reaction
Products: right side of a chemical
reaction
Enzymes provide the surface area to
reduce the activation energy and
allow the reaction to occur
Ex: C6H12O6 + 6 O2  6 CO2 + 6 H2O
Enzymes – organic catalysts = a type of protein
- reduce or eliminate activation energy
- unchanged by the reaction can be used over and over
Letter at the beach example
Lock and Key Theory
1 Enzyme for 1
Reaction:
Hydrolysis or
Dehydration
Affected by temperature, pH and pressure
Synthesis
-denature: changes shape or completely breaks down into amino
acids
- example: fried egg, proteins in egg change color from clear to white
Protein Synthesis
Melanin biosynthetic pathway
Multiple enzymes allow for the
chemical reactions of melanin
production to occur.
If one enzyme does not function
the reaction stops and thus
albinism
The only way an enzyme changes shape
or mutation
is by a DNA
Gene  Protein  Trait
The DNA Song
Crash Course Biology: Carbon
Water
Biological Molecules
Codes for amino acid sequence for
Study Island
protein synthesis
Organic Molecules and Water 3a
and
Enzymes 3b