Biological Molecules

The Building Blocks of Life

 W
O
• Before we begin, get out a piece of paper,
R
put your name on it, and do the following: K
• As review, sketch a diagram of an atom T
and label the particles. O
G
• Sketch a water molecule, and state what E
kind of bonds form between the oxygen T
and hydrogen atoms in water. H
E
R
Which four elements make up about 96%
of living matter?
1. carbon, hydrogen,
81%
nitrogen, oxygen
2. carbon, sulfur,
phosphorous,
hydrogen
3. carbon, oxygen,
sulfur, calcium
13%
4. oxygen, hydrogen,
4% 2%
calcium, sodium
1 2 3 4
 An atom of nitrogen attracts electrons more
strongly than an atom of hydrogen. Which of the
following best describes ammonia (NH3)?
25% 25% 25% 25%
1. The nitrogen is
slightly negative.
2. The nitrogen is
strongly positive.
3. The hydrogens are
slightly negative.
4. The hydrogens are
strongly positive.
1 2 3 4
 Carbon is the backbone of organic molecules.
With an atomic number of 6, carbon can form up
to ___ different ___ bonds.
25% 25% 25% 25%

1. 6; ionic
2. 6; covalent
3. 4; ionic
4. 4; covalent

1 2 3 4
Atoms to Molecules
In our model of scale, remember that the marble
represented a small monomer, such as glucose.
 The FOUR Classes of Large
Biomolecules
• All living things are made up of four classes of
large biological molecules:
• Carbohydrates
• Lipids
• Protein
• Nucleic Acids

• Macromolecules are large molecules composed

of thousands of covalently bonded atoms

• Molecular structure and function are inseparable

 The FOUR Classes of Large
Biomolecules
• A polymer is a long molecule consisting of many
similar building blocks
• These small building-block molecules are called
monomers
• Three of the four classes of life’s organic molecules
are polymers
• Carbohydrates
• Proteins
• Nucleic acids
 One glucose molecule alone
is a monomer.

Two or more
glucose
molecules linked
together can
make a polymer.
 Functional Groups
Functional groups
determine how a
molecule will
interact with other
molecules.

Why does sugar dissolve in water?

The methyl group, consisting of carbon bonded
to hydrogen, is an area of ___ in an organic
molecule.
50% 50%

1. Polarity
2. Non-polarity

1 2
If you see oxygen or nitrogen in the structure of
an organic molecule, expect that area to be:
50% 50%

1. Polar
2. Non-polar

1 2
 The synthesis and breakdown of
polymers
• A dehydration reaction
occurs when two
monomers bond together
through the loss of a
water molecule
• Polymers are
disassembled to
monomers by
hydrolysis, a reaction
that is essentially the
reverse of the
dehydration reaction
 Dehydration Synthesis

Two glucose
molecules ...can bond together
(monomers)... to make maltose
(dimer).
Dehydration Synthesis
 Hydrolysis

A dimer such as ...can be broken

maltose, or any apart into its
other polymer... constituent
monomers.
Hydrolysis
Making/Breaking Molecules
Monomers or
Polymers?
The process The process
occurring between occurring between
C and A is: A and C is:
Hydrolysis Dehydration
Synthesis

What is taken What is given

up here? off here?
H2O H2O

Monomer or
Polymer?
In our model of scale, large chain molecules
(polymers) are represented by the cat.
Carbohydrates
Carbohydrates Serve as Fuel
& Building Material

• Carbohydrates include sugars and the

polymers of sugars

• The simplest carbohydrates are

monosaccharides, or single sugars

• Carbohydrate macromolecules are

polysaccharides, polymers composed of many
sugar building blocks
The Diversity of Polymers
• Each cell has thousands of different
macromolecules

• Macromolecules vary among cells of an

organism, vary more within a species, and vary
even more between species

• An immense variety of polymers can be built

from a small set of monomers
Sugars: Monosaccharides
• Monosaccharides have molecular
formulas that are usually multiples of
CH2O
• Glucose (C6H12O6) is the most
common monosaccharide

• Monosaccharides are classified by

– The location of the carbonyl group
– The number of carbons in the carbon
skeleton
 Monomers
Simple sugars, such as
glucose, are the
monomers of complex
carbohydrates.

Label a hydrogen group

and hydroxyl group on
the glucose diagram.
What are some
properties of these
groups?
What is similar about
these four simple
sugars?
What is different?
 glucose fructose sucrose

What process do you see happening here to create this

glycosidic linkage between the two sugars?

What is the scientific term for a pair of monomers linked

together?
 Sugars: Disaccharides
• A disaccharide is formed when a dehydration
reaction joins two monosaccharides

• This covalent bond is called a glycosidic

linkage
Synthesizing Maltose & Sucrose
 Polysaccharides
• Polysaccharides,
the polymers of
sugars, have
storage and
structural roles
• The structure and
function of a
polysaccharide are
determined by its
sugar monomers
and the positions of
glycosidic linkages
Types of Polysaccharides: Storage
• Starch, a storage
polysaccharide of
plants, consists
entirely of glucose
monomers
• Plants store surplus
starch as granules
within chloroplasts
and other plastids
• The simplest form
of starch is amylose
 Glycosidic linkages between many
sugar molecules create complex
carbohydrates, such as starch.

What is the scientific

term for many
monomers linked
together?
Types of Polysaccharides: Storage

• Glycogen is a
storage
polysaccharide in
animals
• Humans and other
vertebrates store
glycogen mainly in
liver and muscle
cells
Types of Polysaccharides: Structural

• The polysaccharide cellulose is a major

component of the tough wall of plant cells

• Like starch, cellulose is a polymer of glucose,

but the glycosidic linkages differ

• The difference is based on two ring forms for

glucose: alpha () and beta ()
 Cellulose

Hemp
Cotton
Rayon

Dietary
Linen “fiber”
Such Elegance!
What do you see in the structure of cellulose that tells
you that it is a carbohydrate?

How is cellulose similar to starch?

 Cellulose vs. Starch

We can digest starch (amylose) but not cellulose.

What difference do you see that might be the reason
behind this?
 Chitin

Pectin
In general, how
can we describe
complex
carbohydrates?
 Polysaccharide
Random Acts of Biology
• Cellulose in human food passes through the
digestive tract as insoluble fiber

• Some microbes use enzymes to digest cellulose

• Many herbivores, from cows to termites, have

symbiotic relationships with these microbes

• Chitin, another structural polysaccharide, is found

in the exoskeleton of arthropods (crunch!)

• Chitin also provides structural support for the cell

walls of many fungi
Who knew?
 White death?
Some people claim that sugar is harmful, toxic,
or addictive. Is it?

http://ed.ted.com/lessons/how-sugar-affects-the-brain-nicole-avena
Fake sugar?
Complex carbohydrates are:
1. Polymers of simple 50% 50%
sugars.
2. Monomers of
simple sugars.

1 2
True or false: Sugars and starch have a lot
of fat in them.
1. True 50% 50%
2. False

1 2
 W
O
• Look around you. What are some R
specific examples of carbohydrates that K
are in this room right now?
T
• List some specific carbohydrates that O
G
you ate for breakfast. Not the foods that
E
they were in – name the carbohydrates T
themselves. H
E
R
Lipids
Lipids Are Hydrophobic
Lipids are a diverse group of hydrophobic
molecules
• Lipids are the one class of large biological
molecules that do not form polymers
• The unifying feature of lipids is having little or
no affinity for water (water fearing)
• Lipids are hydrophobic because they consist
mostly of hydrocarbons, which form nonpolar
covalent bonds
• The most biologically important lipids are fats,
Fats: Start with a Simple Little
Glycerol Molecule

• Fats are constructed from two

types of smaller molecules:
glycerol and fatty acids
• Glycerol is a three-carbon
alcohol with a hydroxyl group
attached to each carbon
• A fatty acid consists of a
carboxyl group attached to a
long carbon skeleton
Dehydration Rxn 1: Add a Fatty Acid

• Next, add a “fatty acid” through a dehydration

synthesis reaction
• What makes it an acid? The C double bond O,
single bond OH!
Dehydration Rxn 2!!

• Next, add a SECOND “fatty acid” through a

dehydration synthesis reaction
Dehydration Reaction THREE!!!

• The joining
of the C of
the fatty
acid to the
O of the
hydroxyl
group of
the
glycerol is
called an
ester
linkage.
 Label a methyl group and a hydroxyl group on one
of the fatty acids. What are some properties of
these groups?

What process
do you see
happening here
to create these
ester bonds
between the
fatty acid chains
and the glycerol
in this
triglyceride?
 Lipids that are solid
at room temperature
are composed mostly
of saturated fatty
acids.

Stearic acid (found in wax

and lard) and butyric acid
(found in butter) are
examples of saturated fatty
acids.
Lipids that are liquid at
room temperature are
composed mostly of
unsaturated fatty acids.

Oleic acid and linoleic acid

are unsaturated fatty acids
that are common in
vegetable oils.
Saturated vs. Unsaturated
Saturated or Unsaturated?
• Fats made from
saturated fatty acids
are called saturated
fats, and are solid at
room temperature
• Most animal fats are
saturated (lard)
• Saturated fatty
acids have the
maximum number of
hydrogen atoms
possible and no
Saturated or Unsaturated?
• Fats made from
unsaturated fatty acids
are called unsaturated
fats or oils, and are
liquid at room
temperature
• Plant fats and fish fats
are usually
unsaturated
• Unsaturated fatty
acids have one or
more double bonds
Saturated or Unsaturated?
• A diet rich in saturated
fats may contribute to
cardiovascular disease
through plaque deposits

• Hydrogenation is the
process of converting
unsaturated fats to
saturated fats by adding
hydrogen
 What’s a Trans fat?
• Hydrogenating vegetable oils also creates
unsaturated fats with trans double bonds
• These trans fats may contribute more than
saturated fats to cardiovascular disease
Saturated or Unsaturated?
• Certain unsaturated fatty acids are not
synthesized in the human body
• These must be supplied in the diet
• These essential fatty acids include the omega-3
fatty acids, required for normal growth, and
thought to provide protection against
cardiovascular disease
 Essential Fatty Acids
• OMEGA 3
ALA

EPA

DHA
 Essential Fatty Acids
• OMEGA 6
LA

AA

GLA

DGLA
 Trans fats?
Unsaturated fats bend Trans configuration results in
because of the cis an unsaturated fatty acid that
configuration is a straight chain like a
saturated fatty acid

Trans fats are rare in nature. Hydrogenation can create both

saturated and trans fatty acids.
 Fats: Major function is
storage!
• The major function
of fats is energy
storage
• Humans and other
mammals store
their fat in adipose
cells
• Adipose tissue also
cushions vital
organs and
insulates the body
 A puzzle:

Shortening and margarine

labels often brag that their
products are made with healthy,
unsaturated vegetable oils.
Vegetable oils are liquid at room
temperature. So why are
shortening and margarine solid
at room temperature?
 Phospholipids
Saturated or
unsaturated?

Label the phosphate group

on this phospholipid. What
are some properties of this
group?
 Phospholipids
• When phospholipids are
added to water, they self-
assemble into a bilayer,
with the hydrophobic tails
pointing toward the interior
• The structure of
phospholipids results in a
bilayer arrangement found
in cell membranes
• Phospholipids are the
major component of all cell
membranes
 A Single Phospholipid Molecule
Choline
Hydrophilic head

Phosphate

Glycerol
Hydrophobic tails

Fatty acids

Hydrophilic
head

Hydrophobic
tails

(a) Structural formula (b) Space-filling model (c) Phospholipid symbol

Steroids
 Steroids
• Steroids are lipids characterized by a carbon
skeleton consisting of four fused rings
• Cholesterol, an important steroid, is a
component in animal cell membranes
• Although cholesterol is essential in animals,
high levels in the blood may contribute to
cardiovascular disease
Fake fat?

What do you see in this molecular

structure that suggests why Olestra is
not digested? Why might it cause the
symptoms described on the label?
 Olestra
Olestra- (also known by its
brand name Olean) is a fat
substitute that adds no
fat,calories, or cholesterol to
products. It has been used in
the preparation of otherwise
high-fat foods such as potato
chips, thereby lowering or
eliminating their fat content.
 W
O
R
• List some examples of lipids or fatty K
acids – not the foods that contain them,
T
but specific lipids.
O
G
• How are carbohydrates and lipids
E
different from one another? T
H
E
R
 A fatty acid consists of:
1. A chain of carbon 85%
and hydrogen
atoms.
2. A chain of sugar
molecules.
3. A chain of any
carbon-containing
monomers. 7% 9%

1 2 3
Why can’t you mix oil and water?
1. Oil floats on water.
93%
2. Oil is more dense
than water.
3. Oil is non-polar,
while water is
polar.
4. Oil is an organic
molecule, while
water is not. 7%
0% 0%

1 2 3 4
Which of these is the largest
object?
1. A carbon atom. 25% 25% 25% 25%

2. A fatty acid.
3. A phospholipid.
4. A cell membrane.

1 2 3 4
Proteins
 Monomers

Amino Carboxylic acid

group group

Amino acids are the monomers of proteins.

On your diagram, label the amino group and the
carboxylic acid group. What are some properties of
these groups?
 R-groups
determine the
properties of
individual
amino acids.
What process do you see happening here to create this
peptide bond between the two amino acids?

What is the scientific term for many monomers linked

together?
Protein Structure: 4 Levels
• Primary structure consists of its unique
sequence of amino acids
• Secondary structure, found in most proteins,
consists of coils and folds in the polypeptide
chain
• Tertiary structure is determined by interactions
among various side chains (R groups)
• Quaternary structure results when a protein
consists of multiple polypeptide chains
 Primary Structure
• Primary structure,
the sequence of
amino acids in a
protein, is like the
order of letters in a
long word
• Primary structure is
determined by
inherited genetic
information
 Secondary Structure
• The coils and folds of
secondary structure
result from hydrogen
bonds between
repeating constituents of
the polypeptide
backbone
• Typical secondary
structures are a coil
called an  helix and a
folded structure called a
 pleated sheet
Secondary Structure
Tertiary Structure
 Quaternary Structure
• Quaternary structure results when two or
more polypeptide chains form one
macromolecule

• Collagen is a fibrous protein consisting of

three polypeptides coiled like a rope
 Quaternary Structure
• Hemoglobin is a globular protein consisting
of four polypeptides: two alpha and two beta
chains
Some proteins, like keratin, are structural proteins.
Actin and myosin fibers in muscle cells, spider webs, and
silk are also structural proteins.
Some proteins, such as insulin, are hormones.
Some proteins are enzymes that build or break down other
molecules in living cells.
Some proteins are structured to carry or move substances,
such as hemoglobin that carries oxygen, or cell membrane
proteins that move substances across the membrane.
 Heat, acidity, or both can denature proteins. Denaturing
changes the shape of a protein, which changes its
appearance and functionality. Denaturing is what happens
when we fry an egg (egg whites contain albumin protein)
or use acids to turn milk into cheese (milk solids contain
casein proteins).
 The shape of a protein determines its function.

The shape of an individual protein is determined by the

order of amino acids in the primary chain, which affects how
the amino acid chain twists and folds into the final shape of
the protein.

DNA contains the code that instructs the cell machinery to

put amino acids together in a particular order to make a
particular protein. As long as the DNA contains the correct
code, the protein will function. Mistakes in the code
(mutations) change the order of amino acids, which
changes the structure of the protein, which prevents the
protein from carrying out its function.
True or False: Meat is an example
of a protein.
1. True: Meat is an
85%
important dietary
protein.
2. False: Meat is muscle
tissue that is made up
of many different
proteins, lipids, and
other molecules.
15%

1 2
___ bonds are responsible for primary structure
of proteins, while ___ bonds contribute to the
secondary structure.
1. Ionic; covalent 42%
2. Peptide; hydrogen
3. Peptide; covalent
26%
4. Hydrogen; ionic
21%

12%

1 2 3 4
When we say “proteins are made of
amino acids,” it means that:
1. Proteins are larger
33% 33% 33%
than amino acids.
2. Amino acids are
larger than
proteins.
3. Both amino acids
and proteins are
about the same
size.
1 2 3
 W
O
R
• List some examples of specific proteins K
– again, not foods that contain proteins,
T
but specific proteins.
O
G
• Why are there so many different kinds
E
of proteins? T
H
E
R
Nucleic Acids
 Monomers
Label the parts
on this
nucleotide.

Is this a
nucleotide of
DNA or RNA?
How can you
tell?
Nucleotides link together to form nucleic acids. The
sugars bind to the phosphate groups to form the
backbone of the chain.
DNA is two strands of
nucleotides side-by-
side.

What is the type of

bond that forms the
cross-links holding the
two strands together?
 ATP

Adenosine
triphosphate, the
universal energy
carrier, is a single
nucleotide (adenine)
with two extra
phosphate groups
attached.
 DNA is found inside of the
nucleus of a:
1. Cell
33% 33% 33%
2. Atom
3. Both

1 2 3
 Try to fill in this table from memory:

Monomers Polymers Examples

Complex Starch,
Simple sugars
Carbohydrates Cellulose, etc.

Hemoglobin,
Amino acids Proteins
Keratin, etc.

Fatty acids & Fats, waxes,

Lipids
glycerol oils, steroids.

Nucleotide Nucleic Acids DNA, RNA

 W
• Observe the structure of each of these O
monomers and identify them. R
K
1 2
T
O
G
Amino Acid Sugar E
T
3 H
Fatty Acid E
R
• The circled objects in our scale model W
represent... O
Small R
Molecule Chain K
Atom
Molecule
T
O
G
E
T
H
E
R
 Recap
• Atoms of carbon, hydrogen, oxygen, and a
few other elements bond together covalently
to make the biological molecules.
• Monomers (small molecules, such as
glucose) bond together to form polymers
(large chain molecules, such as complex
carbohydrates).
• The four classes of biological molecules are
carbohydrates, lipids, proteins, and nucleic
acids.