Polymer Principles
• Most macromolecules are polymers.
– Polymer = large molecule consisting of many identical
or similar subunits connected together.
– Monomer = subunit or building block molecule of a
polymer.
– Macromolecule = large organic polymer
• Formation of macromolecules from smaller building block
molecules represents another level in the hierarchy of
biological organization.
• Four classes
– Carbohydrates, Lipids, Proteins, Nucleic Acids
Polymer Principles cont’
• Dehydration reaction or Condensation
reaction = polymerization reactions during
which monomers are covalently linked,
producing net removal of a water molecule
for each covalent linkage.
– Process requires energy.
– Process requires biological catalysts or
enzymes.
Polymer Principles cont’
• Hydrolysis = a reaction process that breaks
covalent bonds between monomers by the
addition of water molecules.
– Example: Digestive enzymes catalyze
hydrolytic rxns which break apart large food
molecules into monomers that can be absorbed
into the bloodstream.
Polymer Principles cont’
• Question
– Monomers are linked into polymers by ______
_______, which involve the _________ of a
water molecule.
- Polymers are broken down to monomers by
_______ ________, which involves the _______
of a water molecule.
An immense variety of polymers can be built
from a small set of monomers.
• Structural variation of macromolecules is
the basis for the enormous diversity of life.
– There is unity in life as there are only about 40
to 50 common monomers used to construct
macromolecules.
– There is diversity in life as new properties
emerge when these universal monomers are
arranged in different ways.
Carbohydrates: Fuel and
Building Materials
• Sugars, the smallest carbohydrates, serve
as fuel and carbon sources
– Carbohydrates = organic molecules made of
sugars and their polymers
• Monomers are simple sugars called
monosaccharides.
• Polymers are formed by condensation rxns.
• Classified by the number of simple sugars.
Monosaccharides
• Simple sugar in which C, H, and O, occur in the
ratio of (CH2O).
– Are major nutrients for cells.
• Glucose is the most common.
– Can be produced by photosynthesic organisms from
CO2, H2O, and sunlight.
– Store energy in their chemical bonds which is harvested
by cellular respiration.
– Their carbon skeletons are raw materials for other
organic molecules.
– Can be incorporated as monomers into disaccharides
and polysaccharides.
Characteristics of a Sugar
• An –OH grp is attached to each carbon
except one, which contains a carbonyl grp.
• Size of the carbon skeleton varies from
three to seven carbon. Most common are:
Classification No. of Carbons Example
Triose
3
Glyceraldehyde
Pentose
5
Ribose
Hexose
6
Glucose
Disaccharides
• A double sugar that consists of two
monosaccharides joined by a glycosidic
linkage.
– Glycosidic linkage = covalent bond formed by
a condensation rxn between two sugar
monomers.
• Example: maltose
Disaccharides
• Examples of disaccharides
Disaccharides
Monomers
General Comments
Maltose
Glucose +
Glucose
Important in brewing
beer
Lactose
Glucose +
Galactose
Present in
Milk
Sucrose
Glucose +
Fructose
Table sugar; most
prevalent; transport
form in plants
Polysaccharides
• The polymers of sugars, have storage and
structural.
• Polymers of a few hundred or thousand
monosaccharides.
• Are formed by linking monomers in enzymemediated condensation rxns.
• Two important biological functions:
– Energy storage (starch and glycogen)
– Structural support (cellulose and chitin)
Storage polysaccharide
• Starch = glucose polymer that is a storage
polysaccharide in plants.
– Helical glucose polymer with a  1-4 linkage
– Stored as granules within plant organelles called
plastids
– Amylose, the simplest form, is an unbranched polymer
– Amylopectin is branched polymer
– Most animals have digestive enzymes to hydrolyze
starch
– Major sources in the human diet are potatoes and grains
(e.g. wheat, corn, and friuts)
Storage polysaccharide
• Glycogen = glucose polymer that is a
storage polysaccharide in animals.
– Large glucose polymer that is more highly
branched ( 1-4 and 1-4 linkages) than
amylopectin.
– Stored in the muscle and liver of humans and
other vertebrates.
Structural polysaccharides
• Cellulose = linear unbranched polymer of
D-glucose in  1-4,  1-4 linkages
– Major structural component of plant cell walls.
– Differs from starch in its glycosidic linkages
Starch
Cellulose
Glucose
monomers
 configuration
 1-4 linkage
Glucose monomer
 configuration
 1-4 linkages
Structural polysaccharides
• Chitin
– Structural polysaccharide that is a polymer of
an amino sugar
• Forms exoskeletons of arthropods
• Found as a building material in the walls of some
fungi
• Monomer is an amino sugar, similar to beta-glucose
with a nitrogen-containing group replacing the
hydroxyl on carbon 2
Lipids
• Insoluble in water
• Include fats, oils, and waxes
• Many have three fatty acids attached to a
glycerol molecule. (Triglyceride)
• Fatty acids
– Saturated
– Unsaturated
• Monounsaturated and polyunsaturated
Lipids
• Phospholipids
– Similar to triglycerides except that one of the fatty acid
chains is replaced by a phosphate group.
– Phosphate and glycerol are polar.
– Structural foundation of cell membranes.
• Steroids
– Backbone of four linked carbon rings
– Includes cholesterol and hormones, including
testosterone and estrogen.
Proteins
• Central to almost every life function.
• A protein is a functional molecule that
consists of one or more polypeptides, each
folded into a specific 3D-shape.
– Polypeptide is a polymer of amino acids.
• Monomer = Amino acid
– Review page 53 for the 20 amino acids of
proteins
Overview of Protein Function
review page 52
•
•
•
•
•
•
•
•
Enzymatic proteins
Storage proteins
Hormonal proteins
Contractile and motor proteins
Defensive proteins
Transport proteins
Receptor proteins
Structural proteins
Four Levels of Protein Structure
(review pages 56-57)
• Primary structure
– The number and order (sequence) of amino
acids.
– Dehydration reaction
– Covalent bonding
– Coded by DNA
Four Levels of Protein Structure CONT’
• secondary structure
– Contributes to the protein’s overall
conformation.
– Stabilized by hydrogen bonds between the
oxygen ( with a partial negative charge) of one
peptide bond and the partially positive
hydrogen attached to the nitrogen of another
peptide bond.
Four Levels of Protein Structure CONT’
• secondary structure
– Alpha helix
• Is a coil produced by hydrogen bonding between
every fourth peptide bond (3.6 amino acids per turn)
– Beta pleated sheets
• Sheets of parallel chains folded into accordion pleats
• Regions are held together by either intrachain or
inter chain hydrogen bonds (between adjacent
polypeptide.
• Make up the dense core of many globular proteins
(e.g. lysozyme) and the major portion of some
fibrous proteins (e.g. fibroin, the structural protein
Four Levels of Protein Structure CONT’
• Tertiary structure
– Three-demensional shape of a protein
– Types of bonds contributing to tertiary structure
• Weak interactions
– Shape is stabilized by the cumulative effect of weak
interactions.
» Hydrogen bonding between polar side chains.
» Ionic bonds between charged side chains
» Hydrophobic interactions between nonpolar side
chains in protein’s interior
Four Levels of Protein Structure CONT’
• Tertiary structure
– Strong interactions
• Covalent linkage
– Disulfide bridges form between two cysteine monomers
brought together by folding of the protein.
Four Levels of Protein Structure CONT’
• Quaternary structure
– Structure that results from the interactions
between and among 2 or more polypeptides
chains
• Example
– Collagen = a fibrous protein with three helical
polypeptides supercoiled into a triple helix
– Hemoglobin = globular protein that has four subunits.
Mutation:
Change in the primary structure
(review page 58)
• Sickle-Cell Disease
– Inherited disorder
– A change in one amino acid affects the
structure of the hemoglobin molecule
• Causing red blood cells to deform into a sickle
shape that clogs tiny vessels.
Denaturing Proteins
• The bonds and interactions that maintain the
three-dimensional shape of proteins may be
disrupted by:
– pH
– Salt concentration
– Temperature
• Causing the protein to unravel.
Nucleic Acids
• Informational polymers
• Nucleic acids store and transmit heredity
information
• Two types of nucleic acids
– DNA- deoxyribonucleic acid
– RNA- ribonucleic acid
• Flow of information
– DNA  RNA  protein
Nucleic Acids
• A nucleic acid strand is a polymer of
nucleotides
– Monomer = nucleotide
• Three parts
– Nitrogenous base
» Pyrimidines  cytosine, thymine, and uracil
» Purines  adenine and guanine
– Pentose sugar
– Phosphate group