THE STRUCTURE &
FUNCTION OF LARGE
BIOLOGICAL
MACROMOLECULES
Campbell and Reece CHAPTER 5
Macromolecules are Polymers


polymer: long molecule consisting of many
similar, sometimes identical, building blocks
linked by covalent bonds
monomer: the smaller units that make up a
polymer
Many Monomers Make a Polymer
Making Polymers

2 monomers joined by dehydration reaction
Disassembling Polymers

hydrolysis reaction breaks apart 2 monomers
in a polymer
Diversity of Polymers



possible varieties of macromolecules infinite
only use 40 -50 monomers
small molecules common to all organisms are
ordered into species unique macromolecules
Carbohydrates

Simple Carbohydrates
 Sugars
 Monosaccharides
 Disaccharides

Complex Carbohydrates
 Polysaccharides
Monosaccharides

multiples of the unit CH2O

glucose most common monosaccharide
Monosaccharide Diversity

1.
2.
depending on position of the carbonyl group
in a sugar it is classified as either:
aldose (aldehyde sugar)
ketose (ketone sugar)
Monosaccharide Diversity




3 to 7 carbons
hexose: 6 carbons long
pentose: 5 carbons
triose: 3 carbons
Monosaccharide Diversity



most hexoses and pentoses form rings in
aqueous solutions
used in cellular respiration (especially
glucose)
serve as raw materials for synthesis of amino
acids and fatty acids
 if
not immediately used in these ways used to
build disaccharides or polysaccharides
Forms of Glucose
Alpha Glucose
Beta Glucose
Disaccharides

reaction: 2 monosaccharides joined in a
glycosidic linkage
 covalent
bond formed by dehydration reaction
Disaccharides




2 glucose = maltose (malt sugar)
glucose + galactose
glucose + fructose = sucrose (table sugar)
sucrose: form plants use to transport sugars
from leaves  roots & other
nonphotosynthetic parts of plant
Polysaccharides



1.
2.
polymers of hundreds to thousands of
monosaccharides joined by glycosidic
linkages
function determined by its sugar monomers
& positions of glycosidic linkages
2 types:
storage of monosaccharides to be used for
energy when needed
building material
Storage Polysaccharides

Plants store glucose (the monomers)as starch
(the polymer)
 represents
stored energy
Starch

most is made of α glucose monomers joined
in 1-4 linkages
 simplest

form of starch (amylose) is unbranched
complex starch, amylopectin, has 1-6 linkage
Storage Polysaccharides

Animals: store glucose (the monomers) as
glycogen (the polymer) in 1-4 & 1-6 linkages
 stored
mainly in liver & muscle cells
 humans store about 1 days supply of glucose
this way
Structural Polysaccharides


Cellulose: most abundant organic cpd on
Earth
is polymer of β glucose (makes every
monomer of glucose “upside down” from its
neighbors)
Starch & Cellulose
Starch


many are mostly
helical
digested by
enzymes breaking
its α linkages
Cellulose



never branched
has –OH groups
available for
H-bonds
digested by
enzymes breaking
its β linkages
Cellulose



digested by very few organisms (don’t have
enzymes to do it)
in humans: passes thru GI tract abrading
walls & stimulating mucus secretion along
the way  smoother passage of food thru
not technically a nutrient but is important
“Insoluble Fiber” = Cellulose
Cellulose


Cows: have bacteria and protists in their guts
that have enzymes that can digest cellulose
 nutrients that can be used by cow
Termites unable to digest cellulose in wood
it eats have prokaryotes & protists to break it
down and so termite can use nutrients
Termite Life Cycle
Termites
Chitin



another structural polysaccharide
used by arthropods to build exoskeletons
exoskeletons: made of chitin + calcium
carbonate
Chitin


also in many fungi cell walls
monomer has N group attached
Lipids



large group of hydrophobic molecules
do not have true monomers
Includes:
 Waxes
 Steroids
 Some
Pigments
 Oils, Fats
 Phospholipids
Fats


1.
2.
large molecules assembled from smaller
molecules by a dehydration reaction
2 parts:
Glycerol
Fatty Acid
Glycerol
Fatty Acids


long (16-18) chain of carbons (hydrophobic)
@ one end carboxyl group (hence fatty acid)
Triglyceride

3 fatty acids + glycerol
Saturated & Unsaturated
Saturated Fats


include most animal fats
most are solids @ room temperatures
Unsaturated Fats


fats of plants, fish
usually liquid @ room temperature
Hydrogenated Vegetable Oil


seen on some food labels
means that unsaturated fats have been
synthetically converted to saturated fats to
keep from separating
Plaques

deposits of saturated & trans fats
(hydrogenated vegetable oils with trans
double bonds) in muscularis of arteries
Plaques

lead to atherosclerosis (leading cause of heart
attacks) by decreasing resilience of vessel &
impeding blood flow
Trans Fats


USDA now requires nutritional labels to
include amount of trans fats
some cities & Denmark ban restaurants from
using trans fats
Essential Fatty Acids


cannot be synthesized in body so must be
included in diet
include: omega-3 fatty acids:
 required for normal growth in children
 probably protect against cardiovascular
disease in adults
Omega-3 Fatty Acids
Energy Storage


1 g fat has 2x chemical potential energy as 1 g
of polysaccharide
plants (generally immobile) can store
majority of their energy in polysaccharides
except vegetable oils extracted from their
seeds
Functions of Fat


1.
2.
3.
Plants: storage of energy
Animals:
storage of energy
protect organs
insulation
Phospholipids

essential component of cell membranes
Phospholipids

when added to water self-assemble into lipid
bilayers
Steroids


lipids characterized by a carbon skeleton
made of 4 fused rings
cholesterol & sex hormones have functional
groups attached to these fused rings
Cholesterol in Animals




part of cell membranes
precursor for other steroids
vertebrates make it in liver + dietary intake
saturated fats & trans fats increase
cholesterol levels which is ass’c with
atherosclerotic disease

In plant seeds, the inside of the seed is rich
in lipids (oils). Describe & explain the form
the membrane around a droplet of oil would
need to take:
Proteins



word in Greek from “primary”
account for >50% of dry mass of most cells
instrumental in almost everything organisms
do
Proteins are Worker Molecules
Proteins



humans have tens of thousands of proteins,
each with specific structure & function
all made from 20 amino acids (a.a.)
Proteins are biologically functional
molecules made of 1 or more polypeptides,
each folded & coiled into a specific 3-D
structure
Amino Acid Monomers

all a.a. share common structure:
Amino Acid Structure


alpha carbon: center asymmetric carbon
its 4 covalent bonds are with:
1.
2.
3.
4.
amino group
carboxyl group
H atom
R = variable group= side chain
Amino Acids

http://www.johnkyrk.com/aminoacid.html
20 Amino Acids
R Groups

its physical & chemical properties determine
the unique characteristics of a.a. so affect the
physical & chemical properties of the
polypeptide chain
Peptide Bonds
Polypeptide Backbone


polypeptide chain
will have 1 amino
end (N-terminus)
and 1 carboxyl end
(C-terminus)
R side chains far
outnumber N & C
terminus so
produce the
chemical nature of
the molecule
Protein Structure & Function

polypeptide ≠ protein
Functional Protein

is not just a polypeptide chain but 1 or more
polypeptides precisely twisted, folded, &
coiled into a uniquely shaped molecule
Protein Shape

determined by a.a. sequence
Protein Shape
1.
Globular Protein

2.
roughly spherical
Fibrous Protein

long fibers

when polypeptide
released from
ribosome it will
automatically
assume the
functional shape
for that protein’s
(due to its primary
structure)
Name that Shape
Protein Structure


determines how it functions
almost all proteins work by recognizing &
binding to some other molecule
1st Level of Protein Structure
Secondary Structure


segments of each polypeptide chain that coil
or fold in patterns
result of:
 H-bonds
in polypeptide backbone
 α helix: every 4th a.a. held together by H-bonds
 β pleated: 2 parallel β strands held together by
H-bonds (is what makes spider silk so strong)
Secondary Structure
Tertiary Structure

1.
3-D shape stabilized by interactions between
side-chains
hydrophobic interactions


a.a. with nonpolar side chains usually end up
together at core of protein: result of exclusion
of nonpolar parts by water
once nonpolar side chains away from water,
van der Waals forces hold them together
Tertiary Structure:
Hydrophobic Interactions
Tertiary Structure
2. Disulfide Bridges
 covalent bonds that form between 2 S in side
chains of different a.a.
Quarternary Structure


for proteins that are made of >1 polypeptide
chain
the overall protein structure that results from
aggregation of all polypeptide subunits in
protein
http://www.learner.org/courses/biolo
gy/archive/animations/hires/a_proteo
1_h.html
Protein Structure

http://www.stolaf.edu/people/giannini/flashanima
t/proteins/protein%20structure.swf
Collagen



fibrous protein:
40% of all protein
in human body
3 identical
polypeptides
“braided” into
triple helix
gives collagen its
great strength
Hemoglobin


globular protein
made of 2 alpha & 2
beta subunits
(polypeptides)
each has
nonpolypeptide
part = heme which
has Fe to bind O2
Sickle Cell Disease


due to substitution of one a.a. (valine) for the
normal one, glutamine
causes normal disc-shape of RBC to become
sickle shaped because the abnormal
hemoglobin crystallizes
Sickle Cell Disease


go thru periodic “sickle-cell crises”
angular sickled cells clog small blood vessels
 impedes blood flow  causes pain
Protein Structure

1.
2.
3.

also depends on physical & chemical
environment protein is in:
pH
salt concentration
temperature
all of the above can change weak bonds &
forces holding protein together
Denaturation


process in which a protein loses its native
shape due to the disruption of weak chemical
bonds & interactions
denatured protein becomes biologically
inactive
Denaturation Agents

taking protein out of water  nonpolar
solvent: hydrophilic a.a that were on outer
edge  to core vise versa with hydrophobic
a.a.
Protein Structure


most proteins probably go thru some
intermediate shape stages b/4 achieving their
stable shape
chaperonins: protein molecules that assist in
the proper folding of other proteins
Chaperonins
Misfolded Proteins

ass‘c with:
 Alzheimer’s
 Mad
Cow disease
 Parkinson’s
 Senile Dementia
X-ray Crystallography

used to determine the 3-D shape of proteins
Nuclear Magnetic Resonance
(NMR) Spectroscopy

does not require crystallization of protein
Bioinformatics

uses computers to store, organize, & analyze
data to predict 3-D structure of polypeptides
from a.a. sequences
NUCLEIC ACIDS


1.

1.

are polymers made of monomers called
nucleotides
genes code for a.a. sequences in proteins
DNA
deoxyribonucleic acid
RNA
ribonucleic acid
Nucleic Acid Roles
DNA:
1.
self-replication
2.
reproduction of organism
3.
flow of genetic information: DNA  RNA
synthesis  protein synthesis
Nucleic Acid Roles
RNA:
1.
mRNA



conveys genetic instructions for building
proteins from DNA  ribosomes
in eukaryotic cells means from nucleus 
cytoplasm
prokaryotic cells also use mRNA
Nucleic Acids

polymers of nucleotides (the monomers)
Nucleoside

portion of a nucleotide w/out any phosphate
group(s)
Nitrogenous Bases



1.
each has 1 or 2 rings that include N
are bases because the N atoms can take up
H+
2 families:
Pyrimidines

2.
(1) 6-sided ring made of C & N
Purines

(1) 6-sided ring fused to a 5-sided ring
Pyrimidines
1.
Cytosine
2.
Thymine
3.
Uracil
Purines
1.
Adenine
2.
Guanine
Sugars in Nucleic Acids
added to
1.
Deoxyribose
2.
Ribose
Phosphate Group


added to 5’ C of the sugar
(base was added to 1’ C)
Nucleotide Polymers

1 nucleotide added to next in phosphodiester
linkages
Nucleic Acid Backbone




Phosphodiester
linkages 
repeating pattern of
phosphate – sugar –
phosphate – sugar..
notice:
phosphate end is 5’
sugar end is 3’

Polynucleotides have built-in
direction along their sugarphosphate backbones
DNA bases held together by Hbonds with backbones going in
opposite directions
Linear Order of Bases

specifies start, stop of
transcription/translation and codons
determine primary structure of proteins
(which determines the 3-D structure of a
protein which in turn determines the
function of the protein)
DNA Molecules




dbl stranded (in opposite directions =
antiparallel)
bases held together by H-Bonds
most have thousands – millions base pairs
bases pair using complementary base rules
Complimentary Bases
DNA Molecules
RNA

1.
2.

complementary base pairing occurs between:
2 strands of RNA
2 stretches of same RNA strand
Uracil pairs with Adenine instead of
Thymine (none in RNA)
DNA & Proteins


genes & their proteins document the
hereditary background of an organism
able to expect 2 species that appear to be
closely related based on fossil & anatomical
evidence to also share a greater proportion of
their DNA & protein sequences than do more
distantly related species
Hemoglobin


human & gorilla hgb differ only by 1 a.a out
of 46 in β chain
human & frog differ by 67 a.a.