 Polymers
are large molecules
consisting of many identical or similar
subunits connected together
› Monomer – single building block
 Macromolecules
polymers)
› Carbohydrates
› Lipids*
› Proteins
› Nucleic acids
(large organic
 Specifically
a dehydration reaction
 One monomer loses a hydroxyl and
the other loses a hydrogen
 This reaction is repeated as each
monomer is added
 Requires energy
 Requires enzymes

Process that breaks covalent bonds
between monomers by the addition of
water molecules
› Essentially the reverse of the dehydration
reaction
› A hydrogen from the water bonds to one
monomer, and the hydroxyl bonds to another
› Example: Digestive enzymes catalyze hydrolytic
reactions which break apart large food
molecules into monomers that can be absorbed
by the bloodstream
 Carbohydrates
are organic molecules
made of sugars and polymers of
sugars
 Provide energy and act as building
material
 Building block molecules are simple
sugars called monosaccharides
 Classified by the number of simple
sugars
 Single
sugar (CH2O)
 Major nutrients for cells (glucose most
common)
 Can be produced by photosynthetic
organisms from CO2, H2O and light
 Store energy in their chemical bonds
which is harvested by cellular
respiration
 Their
carbon skeletons are raw
materials for other organic molecules
 Carbon skeleton varies from 3 to 7
carbons
 Can be incorporated as monomers
into disaccharides and
polysaccharides
A double sugar that consists of two
monosaccharides joined by a glycosidic
linkage
 Glycosidic linkage = covalent bond formed
by a condensation reaction between two
sugar monomers

› Maltose (glucose + glucose)
› Lactose (glucose + galactose)
› Sucrose (glucose + fructose)
Polymers of a few hundred or thousand
monosaccharides
 Important biological functions:

› Energy storage (starch and glycogen)
 Starch = glucose polymer that is a storage
polysaccharide in plants
 Glycogen = glucose polymer that is a storage
polysaccharide in animals
› Structural support (cellulose and chitin)
 Cellulose = major structural component of plant cell
walls
 Chitin=carbohydrate used by arthropods for
exoskeletons
 Generally
not big enough to be
considered macromolecules
 Hydrophobic – little or no affinity for
water
 Consist mostly of hydrocarbons
 Includes waxes, pigments, fats,
phospholipids, and steroids
 Main
function is energy storage; also
provides cushioning and insulation
 Triacylglycerol or triglyceride
 Made of glycerol and 3 fatty acids
› glycerol = alcohol with three carbons
› fatty acid = a long hydrocarbon chain
with a carboxyl group
 saturated = no double bonds between
carbons in the fatty acid tail (animal fats)
 unsaturated = one or more double bonds in
the fatty acid tail (vegetable and fish oils)
 Make
up cell membranes
 Similar to fats, but they have only two
fatty acids rather than three
 The hydrocarbon tail is hydrophobic
but the phosphate head is hydrophilic
 Micelle = a phospholipid cluster with
the phosphate heads facing outward
and the hydrophobic tails inward
 When
placed in water, they selfassemble into a bilayer
 Phospholipid Bilayer = hydrophilic
heads are in contact with water,
whereas the hydrophobic tails are in
contact with each other and remote
from water.

Lipids characterized by
a carbon skeleton
consisting of four fused
rings
› Cholesterol is a
precursor from which
other steroids
(including sex
hormones) are
produced
 High levels may
contribute to
atherosclerosis
 Account
for more than 50% of the dry
mass of most cells
 Used for structural support, storage,
transport of other substances, cell
communication, movement, defense
against foreign substances, and
catalysis (enzymes)
Made up of 20 amino acids
 Polypeptides = polymers of amino acids
 Proteins consist of one or more
polypeptides folded and coiled into
specific three-dimensional structures
 Amino acids have a carbon atom
bonded to an amino group, a carboxyl
group, a hydrogen atom, and a variable
group symbolized by R

› The R group (or side chain) differs with each
amino acid
Amino acids are joined by a dehydration
reaction (removal of water) forming a
peptide bond between the carboxyl
group of one amino acid and the amino
group of the other
 Each polypeptide has a unique
sequence of amino acids
 The sequence of amino acids in a
protein is determined by inherited
genetic information (DNA)

A
functional protein is one or more
polypeptides precisely twisted, folded,
and coiled into a unique shape
 Many proteins are roughly spherical
(globular proteins)
 Others are like long fibers (fibrous
proteins)
 A protein’s structure determines its
function
 Basic
sequence of amino acids
 The order is crucial to the function of
the protein
› Sickle cell anemia results from the
substitution of one amino acid in
hemoglobin
› Frederick Sanger discovered insulin’s
primary structure in the late 1940’s

Segments of the polypeptide chain are
repeatedly coiled or folded as a result of
hydrogen bonds at regular intervals
along the polypeptide backbone
› Alpha (α) helix – delicate coil held together
by hydrogen bonding between every fourth
amino acid (found in fibrous proteins)
› Beta (β) pleated sheet – parallel regions are
held together by hydrogen bonds between
adjacent polypeptides
 The
overall shape of a polypeptide
resulting from interactions between
the R groups
› Hydrophobic interaction – the nonpolar
side chains cluster at the core of the
protein away from water (van der Waals
interactions hold them together)
› Disulfide bridges – the sulfur of one
cysteine amino acid binds to the sulfur of
another (-S-S-)
Some proteins
consist of two or
more polypeptides
 Structure in proteins
that results from
interactions
between and
among several
polypeptide chains

 Denaturation
is a process that alters a
protein’s native conformation and
biological activity.
 Occurs when:
› Proteins are transferred to an organic
solvent (ex. ether or chloroform)
› Chemical agents disrupt hydrogen
bonds, ionic bonds, and disulfide bridges
› Excessive heat disrupts weak interactions
Predicting protein conformation based
on amino acid sequence is difficult
because most proteins pass through
intermediate stages in the folding
process
 Chaperone proteins (chaperonins)
temporarily brace a protein while it folds
spontaneously
 Knowledge of protein folding would
allow the design of proteins for specific
purposes


DNA - deoxyribonucleic acid
› Contains coded information that programs
›
›
›
›
all cell activity
Contains directions for its own replication
Is copied and passed from one generation
of cells to another
Found primarily in the nucleus in eukaryotic
cells
Makes up genes that contain instructions for
protein synthesis (direct the synthesis of
mRNA)
 RNA
- ribonucleic Acid
› Functions in the actual synthesis of
proteins coded for by DNA
› Sites of protein synthesis are on ribosomes
› Messenger RNA (mRNA) carries encoded
genetic message from the nucleus to the
cytoplasm
› Flow of genetic information goes from
DNA to RNA to protein

Nucleic acids are polymers of
nucleotides
1. A five carbon sugar (ribose or deoxyribose)
2. A phosphate group
3. A nitrogenous base



Purines – adenine (A) and guanine (G)
Pyrimidines – cytosine (C), uracil (U), and thymine
(T)
Base Pairings: A-T, C-G (in DNA) and A-U,
C-G (in RNA)
 James
Watson and Francis Crick
proposed the double helix structure of
DNA in 1953
› DNA consists of two nucleotide chains
held together by hydrogen bonds
between paired bases and van der
Waals attraction between stacked bases
and wound in a double helix (twisted
ladder)