Biochemistry
Chapter 3
Water
Section 2.3
Structure of Water
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Held together by covalent bonds
2 atoms of H, 1 atom of O
Water is a Polar Molecule
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Definition: a molecule with an
uneven distribution of charge but a
net charge of zero
Water bonds at an angle
Water’s ability to dissolve
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“Like Dissolves Like”
Polar substances can dissolve polar
substances, nonpolar substances
can dissolve nonpolar substances
Questions:
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Why don’t oil and water mix?
Why can water dissolve sugar or
salt?
How does water dissolve a polar
substance?
Answer:
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The + end of water attracts
to the – ion of the substance
The – end of water attracts to the
+ ion of the substance
This breaks the ionic bond of the
substance thus dissolving it
Water’s special bond:

Hydrogen Bond: a weak chemical
bond that exists between the H
atoms and a – charged part of a
different molecule
Water’s special properties:
Due to H-bonds:
1.
Water can cling to itself and other
substances
2.
Water is able to absorb large
amounts of energy without
changing temperatures quickly
Cohesion:
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Definition: When like molecules are
attracted to each other
Ex) surface tension in water
Adhesion:

Definition: the attractive forces
between unlike substances
Capillarity:
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Definition: cohesion and adhesion
working together to move water
molecules up a narrow tube against
the force of gravity
Homeostasis?
1.
2.
3.
The H-bonds in water are the first
bonds to break when an increase
in energy (temp) is applied
It takes a LARGE amount of energy
to break/move water molecules
Thus, the temperature of water
stays fairly constant in a cell even
though there might be a drastic
temperature change outside
Lab time….yeah!
Carbon Compounds
SECTION 3.1
Organic Compounds
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Organic
compounds
contain carbon
atoms
Form covalent
bonds with other
C atoms or to
other elements N, H, and O.
Carbon Bonding


C readily covalently bonds (a bond
forms when electrons are shared)
Each C forms 4 covalent bonds
Large Carbon Molecules


Polymers are made up of many
small, repeating molecules called
monomers.
Macromolecules- large polymers
Condensation Reaction

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A chemical reaction that links
monomers to form polymers
One water molecule is produced
Ex) Glucose and Fructose combine to make Sucrose, table sugar
Hydrolysis

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A chemical
reaction that
breaks down
polymers
Reversal of
condensation
reaction
Usually done by
adding water
ATP – Adenosine Triphosphate

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All of life’s functions require energy
Energy compounds found in cells
Biochemistry
The stuff life is made of!
Section 3.3
The Four Molecules of Life
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1.
2.
3.
4.
Carbohydrates
Proteins
Lipids
Nucleic Acids
All of your body is made up of these
four types of molecules!
The Building Blocks
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Each type of molecules is made up
of smaller parts called monomers.
When 3 or more monomers are
linked together, they form a
polymer.
How to make a macromolecule.
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How do you make a polymer from
many monomers?
CONDENSATION REACTION!
Condensation Reaction:

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The formation of larger molecules
by removing a H+ from one
monomer and a OH- from the other
monomer.
The H+ and the OH- combine to form
the bi-product H2O.
What will break up a large molecule?
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The opposite reaction of
condensation……
HYDROLYSIS REACTION!
The use of water to
break apart
polymers back into
monomers.

Condensation/Hydrolysis
Monomers of the 4 Life Molecules
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1.
2.
3.
4.
Carbohydrates - Monosaccharide
Proteins – Amino Acids
Lipids – Fatty Acids
Nucleic Acids - Nucleotides
How do you make macromolecules
of each monomer?
CONDENSATION REACTION
1. Carbohydrates
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Monosaccharide = monomer, simple
sugar,
ex) fructose, galactose, & glucose C6H12O6
Disaccharide = 2 monomers, double sugar
ex) sucrose (table sugar)
Examples)
________________________________________
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Polysaccharide = 3+ monomers
ex) starch & cellulose (in plants)
glycogen (in animals)
2. Protein
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Amino Acid = monomer, 20
different types
Peptide bond holds amino acids
together
Polypeptide = chains of amino acids
Most DIVERSE group of molecules
Many structures such as muscles, skin, hair, and
biological catalysts (enzymes) are made of proteins.
Enzymes
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Protein molecules that catalyze
(increase the rate of) biochemical
reactions
How Do Enzymes Work?
Animation: How Enzymes Work
3. Lipids

Fatty Acids = monomer
•Hydrophilic
Head - polar
•Hydrophobic
Tail - nonpolar
Complex Lipids
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Saturated Fats - bad
Unsaturated Fats - good
Phospholipids (cell membrane)
Waxes
Steroids
4. Nucleic Acids

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Nucleotide = monomer
Found in the genetic material DNA
& RNA
carries out all of the functions of the
cell