The Structure and Function of
Macromolecules
AP Biology – Chapter 5
What are Macromolecules?
They are ENORMOUS…as far as molecules go.

Many are composed of thousands of atoms
Extremely complex

Shape is often vital to function
Most biological molecules are macromolecules

This does NOT mean that smaller and/or inorganic
molecules are unimportant to life.
Polymers
Monomer

Many smaller subunits that are either similar
OR identical to each other
Polymer is a long molecule

Covalent bonds link monomers (subunits)
Making a Polymer
Dehydration/Condensation Reactions
Joining of monomers with a covalent bond
 Water is lost as a result

Breaking Down a Polymer
Hydrolysis Reactions
Monomers separated by adding water
 Covalent bond between monomers is broken
 For more on dehydration and hydrolysis
reactions, click here.

Variety of Organic
Macromolecules
Relatively few building blocks still lead to
incredible variety in the molecules made
This is due to the ARRANGEMENT of the
molecules – HOW they are put together.
CARBOHYDRATES
Sugars and their
polymers
Elements: C, H, O

H:O always 2:1
Functions



Energy (quick)
Storage of Energy
Building and support
materials
Monosaccharides
MONOMERS of the carbohydrate

Monosaccharide = simple sugar

CH2O

Glucose (C6H12O6) most common

(and arguably most important)
FUNCTION: quick energy and as monomers for
all other carbohydrate molecules

Side note: can function as raw materials for
making other compounds like amino acids and
fatty acids.
Monosaccharides
Can be shown as a linear molecule
More realistic representation is as a ring



Sugars form rings in aqueous solution
Note that each bend in the ring is a carbon atom
Note that Hydrogens and Hydroxyl (OH) groups extend from each
carbon (except one).
Disaccharides
Two
monosaccharides
bound together
 by a ___?__ bond

As in all organic
molecules, these
covalent bonds are
created through
dehydration
reactions.
Examples of Disaccharides
Glucose + Glucose = Maltose
Glucose + Galactose = Lactose
Glucose + Fructose = Sucrose
Examples of Disaccharides
Functions of Disaccharides
Function 1
Transport in plants
 Sugar being transported from leaves to roots is
more safe (resists being consumed by the plant)
when transported as sucrose.

Side note:
Few adult mammals have the necessary
enzymes to break down lactose
 Preserves milk supply for young who need it

Polysaccharides
macromolecule - few hundred to a few
thousand monosaccharides linked
covalently (glycosidic linkages)
FUNCTION 1

Energy Storage
FUNCTION 2

Building and support material
Storage Polysaccharides
Starch

Made only by plants
 (Animals can break down starch , but they cannot
make it)
Storage Polysaccharides
Glycogen
Storage polysaccharide created and used by
ANIMALS
 Found in the liver and muscles
 Highly branched chains of glucose

Only about a day’s supply of glycogen is stored in
the body
 Note: Polysaccharides are NOT the major energy
storage compound in animals that they are in plants

Glycogen – diagram and photo
Structural Polysaccharides
Structural polysaccharides are those that are
used in building physical structures in an
organism
Most often we think of cell walls in plants,
but there are others.
Cellulose
Structural polysaccharide that makes up plant cell
walls
The bulk of the woody part of a plant
Cellulose structure



Long chains of glucose – similar to starch
Glucose molecules are linked differently from starch
Difference makes cellulose indigestible to almost all
organisms EXCEPT bacteria and some other microbes
Starch/Cellulose Comparison
Starch/Cellulose Comparison
Cellulose – detailed diagram
Chitin
Chitin is a structural
polysaccharide found
in



Arthropod
exoskeletons (insects,
crabs, lobsters, etc.)
Cell walls of fungus
Also used to make
strong surgical thread
that decomposes after
healing of the wound.
For More on Carbs…
Click Here
LIPIDS
Elements : C, H, O
Major types




Fats and oils
Waxes
Phospholipids
steroids
Functions




Energy storage
Insulation
Cushioning
Cell communication
Lipid Structure
Composed of two kinds of smaller molecules

Glycerol



Fatty acids




An alcohol
3 carbons each with an –OH group
LONG carbon / hydrogen chains
Carboxyl group at one end
Hydrocarbon tail makes up bulk of the fatty acid
Glycerol linked to 3 fatty acids with ester
bonds/linkages


Ester bond = type of covalent bond
To view formation of lipids, click HERE
Lipid structure
Lipid structure relates to function
Lipids are hydrophobic
Due to the hydrocarbons in the fatty acid “tails”
 Hydrocarbons are NONPOLAR



(Carbon and hydrogen share electrons very equally
with no polarity resulting.)
When lipids are placed in water, water would
rather stick to itself than the lipid.

Lipids and water separate
Saturated vs Unsaturated fats
(fatty acid tail comparison)
Saturated fats
Each carbon is “holding hands” with the max
number of hydrogen atoms
 NO double bonds between carbon atoms of the
fatty acid tails
 Tails are STRAIGHT as a result

Straight tails allow for tight packing
 Solid at room temperature

Saturated fat – diagram
For more on lipids and
saturated/unsaturated
fats, click here
Saturated fat – diagram and
photo
Saturated vs unsaturated fats
Unsaturated fats
At least two carbons in the fatty acid chain are
NOT “holding hands” with the maximum
number of hydrogens they can
 Instead two of the carbons (or more) are
DOUBLY covalently bound to each other.
 This results in a bending of the fatty acid tail

Crooked tails prevent tight packing
 Liquid at room temperature

Unsaturated fat – diagram and
photo
Functions of Fat
Primary function = Energy Storage
One gram of fat stores twice the energy of a
gram of polysaccharide
 Advantageous to animals that have to move
around – unlike plants that can have unlimited
bulk without concern for mobility.
 Cells that store fat – adipose cells

Functions of Fat
Other functions specifically related to FAT
Cushioning
 Insulation

Phospholipids
Structure
Glycerol
 TWO fatty acid tails
 ONE phosphate group – “polar head”

Results in a molecule that is BOTH
hydrophobic AND hydrophilic
Fatty acids are nonpolar and hydrophobic
 Phosphate group is polar and hydrophilic

Phospholipid diagram
Phospholipid
Hydrophilic/phobic
nature causes
phospholipids to
naturally form
membranes when
placed in water
(aqueous solution)
To view membrane
formation click here.
Steroids
Structure


4 fused carbon rings
Various functional groups extend from carbon rings
Functions

Roles in cell membrane structure




CHOLESTEROL
Maintains cell membrane structure in animals
Also is a precursor to other hormones
Cell communication
Steroids - cholesterol
PROTEINS
MANY Important Functions

Structural proteins – support


Storage proteins – storage of amino acids





hemoglobin
Hormonal proteins – coordination of activities


Albumin in egg white; casein in milk
Transport proteins – transport many substances across cell
membranes or through the body


Silk in cocoons/webs; collagen in connective tissue
Insulin – controls concentration of sugar in the blood
Receptor proteins – receive chemical stimuli and respond
Contractile proteins – movement
Defensive proteins – protection against disease
Enzymatic proteins – speed up chemical reactions!!
Variety of Proteins
Variety within the different types of
proteins is staggering!

There are many thousands of different types of
enzymes alone – each specifically designed for
a particular chemical reaction.
Importance of Shape
Conformation – term for the unique 3-D
shape of a protein
Shape is absolutely critical to protein
function!!
Protein Structure
Elements: CHON
Monomers = AMINO ACIDS
POLYPEPTIDE is a polymer of amino acids

Polypeptide may or may NOT be a fully functional
protein
One or more polypeptides configured in it’s
particular shape = a protein
Protein Structure – AMINO
ACIDS
An amino acid consists of 5 components

4 components ALWAYS the same





Carbon atom at center
Hydrogen
Amino group
Carboxyl group
R-group


The R group is the ONLY component that varies among amino
acids.
The R group determines the characteristics of the amino acid
Nonpolar Amino Acids
Polar Amino Acids
Forming a Polypeptide
20 different amino acids exist
Can be assembled in any order
Options for HUGE variety of polypeptides
Forming a Polypeptide
To join two amino acids:
Carboxyl group of one must meet the amino
group of another
 An enzyme will join them via a dehydration
reaction
 The resulting bond is called a peptide bond
 Repeating the process over and over creates a
polypeptide

Forming a Polypeptide
Formation of a Polypeptide
The repeated sequence of atoms that
remains constant from one amino acid to
the next is the polypeptide backbone.
The different appendages attached to the
backbone are the R groups

The reactivity of the R groups with each other
determines many unique properties of each
polypeptide chain
Four Levels of Protein Structure
A functional protein is NOT just a
polypeptide chain

It is one or MORE polypeptide chains precisely
twisted, folded and coiled into a uniquely
shaped molecule
ORDER OF AMINO ACIDS determine the
3-D SHAPE
SHAPE determines how the protein
WORKS.
Four Levels of Protein Structure
Use a piece of scrap
paper
Primary structure

The ORDER of the
amino acids in the
chain
Four Levels of Protein Structure
Secondary Structure



Result from the
regularly repeating
structure of the
backbone
Hydrogen bonds
between the constant
parts of the amino
acids
Results in


Alpha helix (spiral) OR
Beta pleated sheets
(fan)
Four Levels of Protein Structure
Tertiary Structure


Results from interactions
between R-groups
Hydrophobic interactions




Also involves van der
Waals attractions
Disulfide bridges
Hydrogen bonds
Results in COMPLEX
folding and twisting of the
polypeptide
Four Levels of Protein Structure
Quaternary Structure




Results when two or more
polypeptide chains
combine to make a
functional protein
Example – Hemoglobin is
composed of 4 chains.
For a protein structure
animation, click HERE
Or HERE
Overview of Protein Structure diagram
Different representations of a protein’s
conformation - Lysozyme
Environment and Protein
Conformation (SHAPE)
Environment plays an important role in
shape of a protein
Environment unsuitable, protein can
DENATURE

– loss of a protein’s SHAPE (conformation)
What can cause a protein to
denature?
pH

pH changes in the environment can interfere with the ability of a
polypeptide chain to hold its shape by interfering with the hydrogen
bonds or other types of bonds within the molecule
Temperature Extremes

Temperature extremes, especially HOT temperatures, cause an
increase in molecular movement which can cause the protein to lose
its shape
Other causes of denaturing
Changes in salinity
 Moving a protein from an aqueous to some organic solution
 Hydrophilic regions of the protein that were once on the outside
would move inside and vice versa
For more on denaturing of proteins, click HERE.
Or HERE

Denatutration of a Protein diagram
NUCLEIC ACIDS
Genes give the information for constructing
proteins
Genes are made of nucleic acids
64
Two types of Nucleic Acid
DNA

Deoxyribonucleic Acid
RNA

Ribonucleic Acid
DNA
The genetic material inherited from parents
Nucleic Acid Structure
Nucleic Acids (both RNA and DNA) are
polymers
The monomers making up these polymers
are nucleotides
Nucleotide structure
3 parts
Nitrogenous base
 Sugar (ribose; which is a 5-carbon [or
penotose]sugar)
 Phosphate group

Nucleotides – Nitrogenous Bases
There are two
families of
nitrogenous
bases

Pyrimidines




Cytosine
Thymine
uracil
Purines


Adenine
guanine
Shape of the DNA Molecule
Double helix
For an
animation
showing the
structure of
DNA, click
HERE.
http://www.tvcc.edu/depts/biology/HotPot/
Biol%201406/biomolecule_structure.htm