Unit 2
The Chemistry of Life
Learning Targets
 Identify elements common to living things.
 Describe how ions work.
 Compare ionic and covalent bonds
 Recognize the importance of hydrogen bonding.
 Explain why many compounds dissolve in water.
 Compare acids and bases.
 Describe the bonding properties of carbon atoms
 Compare and understand the importance of the four macromolecules:




carbohydrates, lipids, proteins, and nucleic acids.
Describe how bonds break and reform during chemical reactions
Explain why and how chemical reactions release or absorb energy.
Explain the effect of catalysts on activation energy.
Describe and explain how enzymes regulate chemical reactions.
Unit OpenerHow can this plant
digest a frog?
Like other carnivores, the Venus
flytrap eats animals to get nutrients
that it needs to make molecules such
as proteins and nucleic acids. Other
chemical compounds made by plant’s
cells enable the Venus flytrap to digest
the animals that it eats. These
chemicals are similar to the chemicals
that allow you to digest the food that
you eat.
????????
If plants can make their own
food through photosynthesis,
why would a plant species
evolve a mechanism to
capture and eat animals?
The animal must be
supplying nutrients that
the plant cannot get from
other sources.
Venus fly traps grow in
swampy areas that have
nitrogen poor soil. These
plants get the nitrogen
they need for survival by
trapping and digesting
animals.
Video
http://www.youtube.com/watch?
v=O7eQKSf0LmY
What is everything made up of?
 Atoms- the building block of matter
 Matter- anything that takes up space
Atoms are made up of:
Protons-> positively charged
particles and dense
Neutrons-> neutral charge / no
charge
Electrons-> negatively charged
particles and small
Protons and neutrons live in the
nucleus (center of the cell)
Electrons are in the outer levels=
electron cloud
Draw and label the atom
What do the numbers mean?
 Atomic mass= sum of protons and
neutrons in the nucleus
 Atomic number = the amount of
protons and electrons in a neutral atom
Element
A type of atom that cannot be
broken down into simpler
substances.
Can also be a group of atoms of
the same type.
Ex-> gases such as hydrogen and
oxygen. Metals= aluminum and
gold.
Atoms are made up of the
same types of particles, so
what makes one element
different from another?
 Different elements differ in the number
of protons they have.
Atomic number=
number of
protons
Atomic Mass
How many protons does
hydrogen have? Oxygen?
Hydrogen= 1
Oxygen= 8
Energy levels
Different energy levels can hold a
different number of electrons.
1st energy level= hold 2 electrons
2nd level= hold 8 electrons
Stable atoms have a full outermost
energy level
91 elements that occur naturally
4 that make up 96 % of your
body= carbon, oxygen, nitrogen,
and hydrogen
The other 4% are called trace
elements because they are found
in little amounts but we need them
to survive-> such as calcium, iron,
potassium
Why does your blood need
iron?
 To transport oxygen in your blood
Why does your body need
chromium?
 Your cells need it to
break down sugars for
usable energy
Compounds
 Atoms of elements found in organisms are
usually linked or bonded to other atoms=
compound.
 Common compounds= water (H2O), carbon
dioxide (CO2)
Ions
 Atom that has gained or lost one or more
electrons.
 Forms because an atom is more stable when its
outermost energy level is full. The gain or lose
results in a full outer level.
 Either positive or negative
 Atoms with few electrons= lose electrons and
becomes more positive
 Gains electrons= more negative.
NaCl
 Transfers electron from
sodium atom to chlorine
atom
 When sodium loses electron
it becomes positive-> full
charged because it has a
filled outermost energy
level.
 The electron lost goes to
the chlorine ion, causing
the chlorine to become
more negative and have a
full energy level.
 End product is an ionic bond-> bond
that forms when two oppositely
charged particles exchange electrical
forces.
 Opposites attract (+ / -)
What determines whether
an atom becomes a
positive ion or a negative
ion?
 Atoms with few outer electrons tend to lose
electrons and form positive ions; atoms with
almost full outer energy levels tend to gain
electrons and form negative ions.
Molecule
Two or more atoms held
together by covalent bonds.
Covalent Bonds
 The strongest of bonds
 Form when atoms share a pair of
electrons.
 Need 4 electrons to fill its outermost
energy level
CO2= Carbon Dioxide
O
C
O
 An oxygen atom needs 2 electrons to fill its
outer energy level. In Carbon dioxide, carbon
makes a double bond, or shares two pairs of
electrons with each oxygen atom.
Properties of
Water!!!!!
Waters unique
properties allow life
to exist on Earth.
Polar vs. Nonpolar
 Polar: Water and
some gases
 Uneven distribution
of electrons
 Nonpolar= liquids,
CO2, Oxygen, oils,
fats
 electrons are
distributed more
evenly around the
outer shell and
cancel each other
out
They both tend to remain separate that is why
they say “oil and water don’t mix.”
Life depends on hydrogen
bonds
 Water is polar-> Have
regions with a slight
positive and slight
negative charge.
 Waters oxygen atoms
are slightly negative
and hydrogen is slightly
positive= HYDROGEN
BOND
 The weakest of bonds
 Important structures in
DNA and proteins.
Properties of Hydrogen Bonds
 Weakest of the bonds
 High specific heat= water resists changes
in temperature, therefore water must
absorb more heat energy to increase
temperature.
Very important with cells because our cells
release a lot of heat and water absorbs that
heat which allows us to regulate cell
temperatures.
Properties Continue
 Cohesion-> attraction
among molecules of a
substance.
Makes water molecules
stick together.
Ex- beads on a car when
it is washed
Spider walking on top of
the water (surface
tension).
http://www.youtube.com/
watch?v=8O8PuMkiimg
Properties Cont.
 Adhesion-> attraction among





molecules of different
substances.
Water molecules stick to other
things.
Ex- upward curve of the surface
of the water-> graduated
cylinder
Ex- plants transport water up
their roots to their leaves.
http://www.youtube.com/watch
?v=45yabrnryXk
http://www.youtube.com/watch
?v=WpXHpXKZtws
Many compounds dissolve in
water- Universal Solvent
 Molecules and ions can’t take part in chemical
processes inside cells unless they dissolve in
water.
 Materials such as sugar and oxygen cannot
be transported from one part of an organism
to another unless they are dissolved in blood,
plant sap, or water based fluids.
Solution= mixture of substances that is
the same throughout= homogeneous
mixture
 Solvent-> substance
 Solute-> substance
that is present in the
that dissolves.
greatest amount,
 Example= kool aid
and is the substance
powder
that dissolves
solutes.
 Example= Water
Solubility
 The ability of the solute to dissolve into
the solvent.
 Typically measured by how fast or the
rate.
 Temperature increases the rate at
which the solute dissolves.
 Pressure increases the rate
 The nature of the solute and solvent
(what its made up of).
Your plasma (liquid part of
your blood) is 95% water.
Which is the solvent and
solute?
 Solvent= water; Solute is the other 5%
which is made up of proteins, sugars,
minerals, platelets, etc
Why do the solutes such as
proteins and sugars dissolve in
the water of blood plasma?
Answer-> polar= because the
attraction between the water
molecules and the solute molecules
is greater than the attraction
among the molecules of the
solutes.
Sum it up! Properties of Water:
 Hydrogen Bonding- strong cohesion (insects





walking on water)
Capillary Action- water moves upward (Roots
to leaves)
Strong Adhesion- attraction between two
unlike substances
Universal Solvent- dissolves everything
High Specific Heat- cools / heats up slowly to
allow temperatures in organisms to maintain
homeostasis
Expands when freezes making it less dense
1.
What is the most
comment solvent in
everyday life?
1.
2.
3.
4.
A. carbon containing
chemicals
B. ethanol
C. water
D. All of the above
3. What is solubility?
a. The ability of a given
substance(solute) to
dissolve into a
solvent.
b. The ability of a given
substance(solvent) to
dissolve into a
solute.
2. In a solution (which is a
mixture of a solute and a
solvent) which do you
typically have more of?
a. Solute
b. Solvent
c. Same amount of both
4. How does temperature
affect solubility?
a. Solubility is not affected by
temperature.
b. Solubility decreases with
an increase in
temperature.
c. Solubility increases with
an increase in
temperature.
5. How does a solute dissolve into a solvent?
a. Polar solvent molecules separate the
molecules of other polar substances.
b. Polar solvent molecules separate the
molecules of other non-polar substances.
c. Non-polar solvent molecules separate the
molecules of other non-polar substances.
6. What are the main factors that affect solubility?
a. Temperature
b. Pressure
c. Nature of solute and solvent
d. All of the above
Answers
 1. C- Water
 2. B
 3. A
 4. C
 5. A
 6. D
Acids and Bases
 Acids
 Releases a hydrogen
ion (H+) when it
dissolves in water.
 0 to 7= acids
Strong
Acid
 Bases
 Removes H+ ions
from a solution
 7-14= basic
Weak
base
Weak
Acid
Strong
Base
pH of 7=Neutral-> neither acidic or basic
pH Scale (Potential
Hydrogen)
How is Ph regulated in our
bodies?
 Through buffers-> compounds that can bind
to H+ ion when the H+ concentration
increases and can release an H+ ion when
the H+ ion decreases.
 Buffer “locks up or stops” the H+ ions in
order for our bodies to maintain homeostasis.
 Example-> normal Ph of blood is 7.35-7.45
(slightly basic), therefore a small change in
this could really disrupt your cells and can be
fatal.
Carbon Based
Molecules
Carbons unique bonding
properties
 Building blocks of life because they are the
basis of most molecules that make up living
things.
 Organisms obtain energy (food) and turn it
into ATP (cells power source for all life
processes).
 Unique atomic structure because it has four
unpaired electrons on the outer energy level
and can form covalent bonds with up to four
other atoms!!!!!!
Three types of molecular
structures
 Straight Chain
 Branched Chain
 Ring
Monomer / Polymer
Polymer= molecule that contains many
Monomers bonded together.
Monomer=
small
molecular
subunit
How many monomers are above?
Four Carbon Based
Molecules in Living Things
/ Macromolecules
1. Carbohydrates
2. Lipids
3. Proteins
4. Nucleic Acids
Carbohydrates
 Fruits, grains, sugars, starches
 Monosaccharides, Disaccharides,
Polysaccharides
 Made up of carbon, oxygen, and hydrogen in
a 1:2:1 ratio
 When broken down they provide a source of
usable chemical energy for cells
 Major part of plant cell structure too!!!
Monosaccharides
 Monomers
 Simple sugars -> glucose= C6H12O6
Disaccharides
 Two monosaccharides linked together
 Transport forms= organisms use it to
move glucose from place to place
 Ex- Sucrose= common table sugar (made
from glucose and fructose)
 Ex- Lactose= milk sugar (made from
glucose and galactose)
Polysaccharides
 Many monosaccharides linked together
to form long branches or chains.
 Polymers
 Ex- starch and glycogen -> energy
storage in plants and animals
 Ex- Cellulose- cell walls in plants
Lipids
 Nonpolar molecules that are insoluble in water
(they don’t dissolve)
 Examples such as fats, oils (coconut, olive, corn),
waxes, cholesterol, steroids, fatty acids, glycerol,
 Function- Some are broken down for cell use, some
are stored for later energy use, and others are parts
of cell structures.
 Monomer- glycerol
 Polymer- fatty acids
3 Main Lipids
 1. Fats or Triglycerides= energy storage
molecules
Three fatty acids bonded to glycerol
2a. Saturated fatty acids= held
together by a single covalent bond
and is solid at room temperature.
Has the maximum number of hydrogen
atoms possible
2b. Unsaturated fatty acids= one or
more double bonds between the
carbon atoms.
Not saturated with hydrogen atoms
2c. Polyunsaturated- two
or more double covalent
bonds
Good fatty acids
3. Phospholipids
 Form the bilayer of the cell membrane
 One glycerol, two fatty acids, and a
phosphate
 Hydrophobic tails- afraid of water (nonpolar)
 Hydrophilic heads- love water (polar)
Proteins
 Most varied- a part of everything from moving your
leg to digesting your pizza.
 Protein is the polymer made up of monomers called
amino acids.
 Amino acids are referred to as the “building blocks”
of proteins and are thought to be the first
molecules on Earth.
 We use 20 different amino acids to build proteins in our
bodies.
 Your body makes 12 and the others need to be ingested
through meat, beans, and nuts.
Amino Acids
 All have similar structures:
hydrogen atom, an amino
group (NH2), and a carboxyl
group (COOH).
 NH2 and COOH are always
present.
 The R group (side group) is
different for each group
 Central carbon is covalently
bonded to four atoms
(functional group) with one
always being a hydrogen.
Proteins Cont.
 Held together by covalent bonds called peptide bonds.
The bonds form between the amino group of one amino
acid and the carboxyl group of another amino acid.
Peptide bond
•Polypeptide forms between two amino acids
•They are a single chain of three or more amino acids linked
together by peptide bonds.
Functions of Proteins
 1. Catalyzing enzymes- speed up
the rates of reactions
Activate metabolic reactions
Lowers activation energy-> the amount of
energy to get a reaction started
On-going
Needs certain factors-> pH, temperature,
and concentration
Ex- Human enzymes work best at 98.6,
above 104 they fall apart.
 2. Defensive proteins- basis of the bodies
endocrine and immune systems. They attack
invading microbes and cancer cells.
Ex- antibodies attack viruses and bacteria
Ex- fibrinogen = protein that causes your blood
to clot
 3. Storage proteins / Nutrient - bind
with iron and calcium to provide
nourishment for an organism.
 4. Transport proteins- allows larger
molecules to move in and out of cells.
Ex- Hemoglobin= carries oxygen
Ex- Myoglobin= carries oxygen to muscles
 5. Support Proteins- provide structural support
and protection.
Ex- Keratin in your hair, skin, and nails
Ex- Fibrin- allows your blood to clot
Ex- Collagen and elastin- major components of
connective tissue
6. Motion Proteins such as myosin and actin
cause muscles to contract or change shape.
7. Messenger proteins- allow different cells to
communicate.
Ex- Hormones- regulate body functions
Ex- Insulin- regulates glucose levels
Ex- Vasopressin- tells your kidneys to reabsorb
water
Nucleic Acids
 Detailed instructions that build proteins and are
stored in extremely long carbon based molecules.
 Nucleic acid = polymer
 Nucleotides = monomer
 Nucleotides are made up of: sugar, phosphate
group, and a nitrogen base (Adenine, thymine,
guanine, and cytosine.
 Two types= DNA and RNA
 ONE FUNCTION!!!!!-> DNA and RNA work together
to make proteins. DNA passes on genetic
instructions to RNA. RNA decodes and turns the
genetic information into a protein.
 DNA is the basis of genes and heredity.
Chemical Reactions
 When substances are changed into
different substances by breaking and
forming chemical bonds.
Reactants vs. Products
Reactants
Label
Them!!!!
Products
What causes bonds in oxygen
and glucose molecules to
break?
 Energy is added that causes the bonds
to break into oxygen and glucose.
 Each bond requires a different amount
of energy= Bond Energy
What happens when new
bonds form in carbon dioxide
and water?
 When new bonds form, energy is
released and this energy that is
released is equal to the amount of
energy that breaks the same bond.
 Sometimes bonds can form a chemical
equilibrium, meaning they are reversible
and the same on both sides of the
equation.
Example of Equilibrium
 Blood cells and
plasma transport
materials throughout
the body. Carbonic
acid dissolves in the
blood so that carbon
dioxide can be
transported to the
lungs.
Chemical reactions release or
absorb energy
 Energy added = breaks chemical bonds
 Energy released= new bonds form
 Energy is released or absorbed and in
different amounts.
Activation energy
Amount of energy that needs to
be absorbed for a chemical
reaction to start.
Ex.- the energy you would need
to push a rock up a hill.
Exothermic
Releases more energy than it absorbs
Excess energy is typically given off in
heat or light
Reactants have more energy than
products
Ex- firefly squid, fireflies, cellular
respiration (releases usable energy as
well as keep your body warm).
Endothermic
Absorbs more energy than it
releases
Products have more energy than
reactants
Example- photosynthesis-> plants
absorb energy from the sun and
use that energy to make simple
and complex carbs.
Enzymes
How did the Venus Flytrap
digest the frog?
Enzymes-> type of protein
that helps start and run
chemical reactions in living
things.
Break down food into smaller
molecules that the body can
use.
What is activation energy?
The energy needed to get
things started
 Most of the time the activation energy for a
chemical reaction comes from an increase in
temperature-> sometimes the process is
very slow.
 In order to speed the process up substances
called catalysts decrease the activation
energy needed to start the chemical reaction
-> in the end it increases the chemical
reaction.
 When a catalyst (ex- enzymes) is present
less energy is needed and products form a
lot faster.
What are two functions of
catalysts in chemical reactions?
1. Decrease activation
energy
2. Increase reaction time.
Enzymes
 Definition= catalysts for chemical reactions in living
things (made by proteins)
 Reactants are usually found at very low
concentrations in the body, but really need to occur
quickly.
 Almost all are proteins= long chains of amino acids
 Each one depends on its structure to function
 Temperature, concentration, and pH can affect the
shape, function, rate, and activity of the enzyme.
 Work best at normal body temperature
 If temperature is a little elevated then the
hydrogen bonds will fall apart, the
enzymes structure will change, and its
ability to function will be lost.
 This is the reason why a high
temperature / fever is very dangerous to
a person.
Examples of enzymes in action
 Amylase is an enzyme in saliva that breaks
down starches into simpler sugars. Without
amylase it would take a million times slower
for you to chew, swallow, and digest your
food.
 Blood cell engulfing a pathogen
CHEMICAL ACTED
UPON
PRODUCTS
Lipase
Fats & oils
Glycerol & fatty
acids
Amylase
Starch
Maltose
Maltase
Maltose
Glucose
Pepsin
Protein
Polypeptides
Protease
Polypeptides
Amino acids
Catalase
Hydrogen
peroxide
Water and oxygen
ENZYME
 The structure is so important because each
enzyme’s shape is specific to a certain
reactant= allows them to fit perfectly
together just like a key fits into a lock
 Specific reactant an enzyme acts on are
called substrates
 The sites where substrates bind to enzymes
are called active sites.
 Enzymes bring substrate molecules close
together, then they decrease activation
energy, substrates attach together and their
bonds are weakened, and then the catalyzed
reaction forms a product that is released
from the enzyme.
Videos
 http://highered.mcgraw-
hill.com/sites/0072495855/student_vie
w0/chapter2/animation__how_enzymes
_work.html
 http://www.youtube.com/watch?v=Nd
MVRL4oaUo
Reflection
 On a sheet of paper, review the three
parts of the lock and key model and write
a paragraph (3-5 sentences) describing
the analogy. Consider why the model is
described as a lock and key. Also identify
the different parts and what happens to
each part after the reaction is complete.
You may use your notes