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Chapter 3
Biochemistry
Water
• Water has 4 important properties.
• Water is polar.
• Water has hydrogen bonding.
• Water is cohesive.
• Water is adhesive.
Polarity
• Many of water’s biological functions stem from
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its chemical structure.
The hydrogen and oxygen in water share
electrons with covalent bonds.
These atoms do not share the electrons equally.
Since the oxygen atom is bigger than the
hydrogen atoms, the electrons tend to hang
around the oxygen atom more often.
This gives oxygen a small negative charge and
the hydrogen a small positive charge.
• A polar molecule is when opposite ends
have opposite charges. Not charges like
ionic bonds but smaller attractions that
sometimes only water has.
Being polar leads to other things
like………
• Hydrogen bonds
• This occurs when the slightly positive
hydrogen atom is attracted to a slightly
negative oxygen atom of another water
molecule, it is a very weak attraction.
hydrogen
oxygen
Cohesion
• This occurs when molecules of the same
kind stick to one another
Cohesion creates surface tension.
Water is very sticky!
Adhesion
• This is when molecules that are not alike
are attracted, example, water to walls of a
test tube, or plant walls
• When you see adhesion, think adhesive,
sticky.
Capillarity
• This is when water
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goes up a small,
narrow tube like a
plant stem or paper
towel.
Adhesion makes this
possible.
Water’s Unique Properties
• Water has 4 unique properties.
Water is polar.
4
1
Water makes hydrogen
bonds.
Water is cohesive.
2
Water is
adhesive.
3
Density of Water is Special!
• Water is one of the only substances on Earth in
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which the solid phase is less dense than the
liquid phase!
Because of this, life can exist in many places.
When winter comes, the ice floats
and keeps fish safe.
ICE
Ouch!
If ice was actually denser than
water…….
I wish I
could get to
safer water
below!
Temperature Moderation
• Water must gain or lose a relatively large
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amount of energy for its temperature to change.
When water is heated, most of the thermal
energy that the water initially absorbs breaks
the hydrogen bonds between the molecules.
When the bonds are broken, the thermal energy
is released and increases the motion of the
molecules.
Water’s ability to absorb large amounts of
energy helps keep cells at an even temperature
despite temperature changes in the
environment.
Carbon Compounds
• A carbon atom has 4 electrons in its outer
level which means it can create 4 bonds
with any other atoms including itself.
• This makes carbon an excellent backbone
for many organic molecules.
• Carbon can even form rings and double
and triple bonds!
Functional Groups
• A functional group is a group of atoms
that influence the properties of the
molecules they compose.
• Alcohol is a functional group that has
oxygen and hydrogen attached.
• Alcohols can cause blindness or even
death when consumed.
• Some alcohols are important to assemble
certain molecules in the body.
Large Carbon Molecules
• In large carbon compounds, the molecules
are built up from smaller, simpler
molecules called monomers.
• Monomers can bind together to create
larger, more complex molecules called
polymers.
• Large polymers are called
macromolecules.
How are polymers made and
broken?
• Monomers link together in a condensation
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reaction.
When two monomers combine, water is
released.
When polymers are broken, it is called a
hydrolysis reaction.
Water is broken into two parts and breaks the
bonds that holds the monomers together.
Energy Currency
• Life processes require energy.
• This energy is available to life in the form
of a compound called ATP.
• ATP has three phosphates on the molecule
and when one phosphate is broken off,
energy is released.
Carbohydrates
• A monomer of a carbohydrate is called
monosaccharide.
• A monosaccharide is a simple sugar.
• Two monosaccharides form a disaccharide.
• A polysaccharide is a complex molecule
composed of three or more
monosaccharides.
• What are some carbs?
Proteins
• Proteins are organic compounds made from
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monomers called amino acids.
There are 20 different amino acids.
The differences between the amino acids are
their R groups.
Two amino acids bond to form a dipeptide.
In a condensation reaction, two amino acids
form a covalent bond called a peptide bond.
Long chains of amino acids are called
polypeptides.
What are some proteins?
Enzymes are a special kind of
protein.
• Enzymes are proteins that are important
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catalysts for chemical reactions.
Enzyme reactions depend on the physical fit
between the enzyme and the substrate.
The substrate is the reactant being catalyzed.
Enzymes may fail to work when the temperature
isn’t correct.
Other chemicals and pH are also a factor.
Affects on Enzymes
• Temperature-raising of lowering
temperature can cause an enzyme to
malfunction
• Denature-a protein unravels when it gets
too hot
• A change in pH can decrease the ability of
an enzyme to function.
• A foreign chemical or metal can decrease
the ability of an enzyme to function.
Lipids
• Lipids are large, non polar molecules that
do not dissolve in water.
• Fatty acids are unbranched carbon chains
that make up most lipids.
• Hydrophilic-water-loving, molecules
dissolve in water
• Hydrophobic-water-fearing, molecules do
not dissolve in water
Types of Lipids
• A triglyceride is composed of three molecules of
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fatty acids joined to an alcohol called glycerol.
Phospholipids have two fatty acids joined with
glycerol.
Phospholipids are contained in the cell
membrane and form a double layer to create a
barrier between the inside and outside of cell.
A wax is a type of structural lipid.
A steroid has 4 carbon rings. Cholesterol is an
example. Steroids are also hormones and very
important for life.
Types of Fats(Lipids)
• A saturated fat has all available bonds used by
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hydrogen.
Saturated fats are solid at room temperature
and are all single bonded, straight chains
Unsaturated fats have a double bond which
means not all available bonds are taken by
hydrogen.
Unsaturated fats are generally liquid at room
temperature and are healthier.
Nucleic Acids
• Nucleic acids are large and complex organic
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molecules that store important information in
the cell.
RNA stores and transfers information to make
proteins.
DNA contains information that is essential for
cell activities.
Both RNA and DNA are composed of monomers
called nucleotides.
A nucleotide has 3 components: a phosphate
group, a sugar and a nitrogen base.
Nucleotide
DNA
Essential Questions
• 1. Describe the structure of the water
molecule.
• 2. What are two properties of water that
are caused by hydrogen bonding?
• 3. What is an organic compound?
• 4. Define functional group and give an
example.
Essential Questions
• 5. How does a polymer form?
• 6. How does a polymer break down?
• 7. What are the 4 classes of organic
compounds? Give an example of each.
• 8. Explain the relationship between
enzyme and substrate.
• 9. What affects the ability of enzymes to
work?